Addiction

"Addictive" redirects here. For other uses, see Addiction (disambiguation) and Addictive (disambiguation).

Not to be confused with Addition.

Addiction
Brain positron emission tomography images that compare brain metabolism in a healthy individual and an individual with a cocaine addiction
Specialty	Psychiatry, clinical psychology, toxicology, addiction medicine
Symptoms	Recurrent compulsion to engage in a rewarding activity despite negative consequences
Complications	Suicide, overdose (if drugs), depression, coma
Risk factors	Family history, adverse childhood experiences, attention deficit hyperactivity disorder
Treatment	Cognitive behavioral therapy, behavior modification, medication

Addiction is a neuropsychological disorder characterized by a persistent and intense urge to use a drug or engage in a behavior that produces an immediate psychological reward, despite substantial harm and other negative consequences. Repeated substance use produces long-lasting changes in brain networks involved in reward, executive function, stress reactivity and mood. These changes underlie both the intense drive to use a substance and the reduced capacity to control that urge. It is therefore understood as a brain disorder arising from a complex mix of psychosocial and neurobiological factors. A number of researchers argue that this framing is incomplete, and that addiction is better understood as learned behavior shaped by choice and social context.

Addiction takes both substance and non-substance forms. Substance addictions include alcoholism, cannabis addiction, amphetamine addiction, cocaine addiction, nicotine addiction and opioid addiction. The DSM-5-TR recognizes only gambling disorder as a behavioral (non-substance) addiction and lists internet gaming disorder as a condition for further study, while the ICD-11 additionally classifies gaming disorder as a disorder due to addictive behaviors. Other candidate behavioral addictions, and the question of whether food can be addictive, are debated in the research literature but are not recognized in either manual. Across these forms, addiction is defined less by any single symptom than by a pattern: impaired control over the substance or behavior, increasing priority given to it over other activities, and continued use despite harm, accompanied for many substances by tolerance and withdrawal. It carries a substantial risk of further illness and early death, most immediately from overdose, and co-occurring psychiatric conditions are common.

Genetic and environmental factors each account for roughly half of an individual's risk of developing an addiction. Genetic vulnerability is polygenic, reflecting the small combined effects of many common variants rather than any single gene. Environmental contributors include adverse childhood experiences, chronic stress, family and peer influences, socioeconomic constraint and the availability of substances, and adolescence is a period of heightened vulnerability. At the level of mechanism, addiction is described as a recurring cycle in which dopaminergic signalling gives a drug and its associated cues a strong pull on attention and behavior, brain stress systems become overactive as ordinary pleasures are muted, and reduced prefrontal cortex control leaves craving poorly restrained.

Addiction is diagnosed clinically. The DSM-5-TR grades substance use disorder as mild, moderate or severe and treats severe substance use disorder as synonymous with drug addiction. The ICD-11 instead distinguishes a harmful episode of use, a harmful pattern of use, and dependence. Prevention approaches with the strongest supporting evidence include family skills programs, school-based personal and social skills education, and policies that limit availability and raise price. Addiction is managed as a chronic, relapsing condition, usually combining medication, where an effective one exists, with psychological and social support. Effective medications are available for opioid, alcohol and tobacco use disorders, but none is approved for stimulant use disorder, for which psychosocial treatment remains the mainstay. Harm reduction measures address the damage associated with continued use. Outcomes vary widely: an estimated 35–54% of people with a substance use disorder reach remission, though typically only after many years. The Global Burden of Disease Study estimated around 100 million cases of alcohol use disorder worldwide in 2016, followed by opioid and cannabis dependence, and drug use was one of only three risk factors whose age-standardized attributable burden rose between 2010 and 2023. Addiction carries substantial economic and social costs, and anthropological and structural accounts situate heavy drug use within cultural norms and unequal distributions of power.

Signs and symptoms

Addiction is defined less by any single symptom and more by a pattern, including impaired control over the substance or behavior, increasing priority given to it over other activities, and continued use despite harm. Impaired control appears as using more or for longer than intended, persistent unsuccessful attempts to cut down, and a great deal of time spent obtaining, using or recovering. Social impairment follows, with failure to meet obligations at work, school or home, and the abandonment of former activities. Risky use (continuing despite knowledge of physical or psychological harm) and, for many substances, tolerance and withdrawal, complete the picture. Specific physical and behavioral signs vary widely by substance and are covered in the articles on individual substance use disorders.

Complications

Acute confusional state caused by alcohol withdrawal, otherwise known as delirium tremens

Addiction carries a substantial risk of further illness and of early death. The most immediate danger is overdose, which for opioids and other sedatives acts by suppressing breathing. Injecting drug use also carries a risk of blood-borne infection, including HIV and hepatitis C. Long-term use damages particular organ systems depending on the substance, with liver cirrhosis and cognitive impairment following sustained heavy drinking and lung disease following tobacco smoking.

Psychiatric conditions frequently co-occur with addiction, and each worsens the outlook for the other, so current guidance is that both be treated at the same time rather than one after the other. Loss of pleasure in ordinary activities (anhedonia) is common and is associated with mood disorders. Globally, alcohol use accounted for an estimated 99.2 million disability-adjusted life years in 2016 and drug use for 31.8 million.

Types

Substance use disorder

Main article: Substance use disorder

Further information: Substance abuse and Substance-related disorder

Addiction and dependence glossary
addiction – a neuropsychological disorder characterized by a persistent and intense urge to use a drug or engage in a behavior that produces natural reward addictive drug – psychoactive substances that with repeated use are associated with significantly higher rates of substance use disorders, due in large part to the drug's effect on brain reward systems dependence – an adaptive state associated with a withdrawal syndrome upon cessation of repeated exposure to a stimulus (e.g., drug intake) drug sensitization or reverse tolerance – the escalating effect of a drug resulting from repeated administration at a given dose drug withdrawal – symptoms that occur upon cessation of repeated drug use physical dependence – dependence that involves persistent physical–somatic withdrawal symptoms (e.g., delirium tremens and nausea) psychological dependence – dependence that is characterized by emotional-motivational withdrawal symptoms (e.g., anhedonia and anxiety) that affect cognitive functioning. reinforcing stimuli – stimuli that increase the probability of repeating behaviors paired with them rewarding stimuli – stimuli that the brain interprets as intrinsically positive and desirable or as something to approach sensitization – an amplified response to a stimulus resulting from repeated exposure to it substance use disorder – a condition in which the use of substances leads to clinically and functionally significant impairment or distress drug tolerance – the diminishing effect of a drug resulting from repeated administration at a given dose

The DSM-5 discourages using the term "drug addiction" because of its "uncertain definition and its potentially negative connotation" and prefers the term "substance use disorder" to describe the wide range of the disorder, from a mild form to a severe state of chronically relapsing, compulsive pattern of drug taking.

Substance use disorder is one of the substance-related disorders. It is a long-term, relapsing condition in which a person continues seeking and taking a substance despite the harm it causes. Repeated use alters the brain circuits that handle reward, stress and self-control, which is why cutting down becomes harder over time. The substances most often involved are alcohol, nicotine, cannabis, opioids, cocaine and amphetamines. Use may begin socially, or follow from a prescribed medication. No single theory accounts for substance use disorder on its own. Phenomenological, operant and classical conditioning, cognitive, and cue reactivity models each explain part of it.

Behavioral addiction

Main article: Behavioral addiction

The term behavioral addiction refers to a compulsion to engage in a natural reward despite adverse consequences.

Addiction can exist without psychotropic drugs, an idea that was popularized by psychologist Stanton Peele. These are termed behavioral addictions. Such addictions may be passive or active, but they commonly contain reinforcing features, which are found in most addictions. Sexual behavior, eating, gambling, playing video games, and shopping are all associated with compulsive behaviors in humans and have been shown to activate the mesolimbic pathway and other parts of the reward system. Diagnostic manuals recognize only some of these as disorders. Gambling disorder is the only behavioral addiction classified as a clinical disorder in the DSM-5-TR, which lists internet gaming disorder as a condition requiring further study; the ICD-11 classifies both gambling disorder and gaming disorder as disorders due to addictive behaviors. Compulsive sexual behavior disorder, compulsive buying–shopping disorder and problematic use of social media are discussed in the research literature as candidate addictive disorders, but are not currently classified as addictions in either manual.

Food addiction

Main article: Food addiction

Whether food can be addictive is disputed. Neither the DSM-5-TR nor the ICD-11 recognises a food or eating addiction, and researchers disagree about whether the concept is best framed as an addiction to specific foods, a pattern of disordered eating, or neither. Proponents argue that ultra-processed foods high in refined carbohydrate and fat meet the criteria conventionally used to identify an addictive substance, because processing delivers these nutrients faster and in higher concentrations than they occur in nature. Critics respond that no single constituent has been isolated as the addictive agent, unlike the case for a drug. Most research uses the Yale Food Addiction Scale, which applies the DSM-5 criteria for substance use disorder to eating. Food addiction as measured this way overlaps with, but is not the same as, binge eating disorder: not everyone with an eating disorder screens positive, and not everyone screening positive has a diagnosed eating disorder.

Causes

Further information: Addiction vulnerability

Several genetic and environmental risk factors exist for developing an addiction. Genetic and environmental risk factors each account for roughly half of an individual's risk for developing an addiction; the contribution from epigenetic risk factors to the total risk is unknown. Even in individuals with a relatively low genetic risk, exposure to sufficiently high doses of an addictive drug for a long period of time (e.g., weeks–months) can result in an addiction. Adverse childhood events are associated with negative health outcomes, such as substance use disorder. Childhood abuse or exposure to violent crime is related to developing a mood or anxiety disorder, as well as a risk of substance dependence.

While regarded biomedically as a neuropsychological disorder, addiction is multi-layered, with biological, psychological, social, cultural, and spiritual (biopsychosocial–cultural–spiritual) elements. A biopsychosocial–cultural–spiritual approach fosters the crossing of disciplinary boundaries, and promotes holistic considerations of addiction.

Ethnographic engagements and developments in fields of knowledge have contributed to biopsychosocial–cultural–spiritual understandings of addiction, including the work of Philippe Bourgois, whose fieldwork with street-level drug dealers in East Harlem highlights correlations between drug use and structural oppression in the United States.

Genetic factors

Main articles: Epigenetics of cocaine addiction and Molecular and epigenetic mechanisms of alcoholism

Further information: Alcoholism § Genetic variation, History of drinking, History of smoking, and Prevalence of tobacco use

Genetic factors, along with socio-environmental (e.g., psychosocial) factors, have been established as significant contributors to addiction vulnerability. Addiction is substantially heritable. Twin and adoption studies estimate the heritability of alcohol use disorder at approximately 50%, with comparable estimates across other substances. This risk is polygenic: it reflects the combined small effects of many common variants rather than any single gene.

Genome-wide association studies (GWAS) are used to examine genetic associations with dependence, addiction, and drug use, and have begun to map this architecture, and distinguish loci associated with a broad general liability to addiction across substances from loci conferring risk for a specific drug. These studies rarely identify genes from proteins previously described via animal knockout models and candidate gene analysis. Instead, large percentages of genes involved in processes such as cell adhesion are commonly identified. The important effects of endophenotypes are typically not capable of being captured by these methods. Genes identified in GWAS for drug addiction may be involved either in adjusting brain behavior before drug experiences, subsequent to them, or both. Individual common variants each contribute only a small increment of risk, so genetic vulnerability is best understood as an aggregate rather than as the effect of any identified gene.

Environmental factors

Environmental risk factors for addiction are the experiences of an individual during their lifetime that interact with the individual's genetic composition to increase or decrease his or her vulnerability to addiction. For example, after the nationwide outbreak of COVID-19 in China, more people quit (vs. started) smoking. People who smoke, on average, reduced the quantity of cigarettes they consumed. More generally, several different environmental factors have been implicated as risk factors for addiction, including various psychosocial stressors. The National Institute on Drug Abuse (NIDA) and studies cite lack of parental supervision, the prevalence of peer substance use, substance availability, and poverty as risk factors for substance use among children and adolescents. The brain disease model of addiction posits that an individual's exposure to an addictive drug is the most significant environmental risk factor for addiction. Many researchers, including neuroscientists, indicate that the brain disease model presents a misleading, incomplete, and potentially detrimental explanation of addiction.

The psychoanalytic theory model defines addiction as a form of defense against feelings of hopelessness and helplessness as well as a symptom of failure to regulate powerful emotions related to adverse childhood experiences (ACEs), various forms of maltreatment and dysfunction experienced in childhood. In this case, the addictive substance provides brief but total relief and positive feelings of control. The Adverse Childhood Experiences Study by the Centers for Disease Control and Prevention has shown a strong dose–response relationship between ACEs and numerous health, social, and behavioral problems throughout a person's lifespan, including substance use disorder. Children's neurological development can be permanently disrupted when they are chronically exposed to stressful events such as physical, emotional, or sexual abuse, physical or emotional neglect, witnessing violence in the household, or a parent being incarcerated or having a mental illness. As a result, the child's cognitive functioning or ability to cope with negative or disruptive emotions may be impaired. Over time, the child may adopt substance use as a coping mechanism or as a result of reduced impulse control, particularly during adolescence. Many children who experience abuse go on to develop an addiction in adolescence or adult life. This pathway towards addiction that is opened through stressful experiences during childhood can be avoided by a change in environmental factors throughout an individual's life and opportunities of professional help.

Social and environmental influences include family dynamics, early and adverse experiences, socioeconomic status, peer networks, and cultural norms. Adverse childhood exposures and maladaptive developmental trajectories are robust environmental influences on the development of alcohol use disorder, and adverse childhood experiences are recognised more generally as a social determinant of vulnerability to substance use disorders. Social networks exert a bidirectional influence, while wider sociocultural factors (including public-health control policies and the social determinants of health) shape both exposure and outcome. Because social risk factors are modifiable, prevention that targets them in childhood and adolescence can reduce the risk of later disorder. Together, these levels of analysis present addiction as a dynamic condition emerging from the interaction of neurobiological processes, individual psychological traits and broader social environments. Social factors act largely through chronic stress, peer modelling, socioeconomic constraint and the availability of substances, influencing both the likelihood of exposure and the risk of escalation or relapse.

Stress and addiction

Stress can play a central and key role in the development and persistence of addiction. It can influence neurophysiological pathways, decision-making processes, and relapse risk. Acute and chronic stress can activate the hypothalamic pituitary adrenal gland, which can result in elevated cortisol and corticotropin-releasing factor. These hormonal changes alter reward processing and increase the motivational value of substances, mainly those that temporarily reduce negative affect.

In preclinical models, repeated stress exposure aids dopamine release in the nucleus accumbens and sensitizes the mesolimbic reward system, increasing the reinforcing aspects of drugs. Chronic stress also disturbs glutamatergic signaling in the prefrontal cortex, which impairs executive functions including inhibitory control and self-regulation. These changes increase the susceptibility to compulsive drug seeking and decrease the ability to ignore conditioned cues that are associated with substance use.

Stress can also be one of the most reliable predictors of a potential relapse. Human neuroimaging studies show that stress-induced activation of the amygdala and reduced prefrontal cortex regulation correlate with self-reported craving and subsequent return to use. Individuals that have a history of trauma or chronic social stress (things like discrimination, poverty, or unstable housing) show an increased risk for substance use disorders due to both neurobiological sensitization and behavioral coping responses.

Stress interacts very strongly with reward circuitry and decision-making systems; this means many treatment approaches integrate stress-reduction strategies. These include cognitive behavioral therapy, mindfulness-based interventions, and medications targeting stress-related neurochemistry.

Social control theory

Main article: Social control theory

According to Travis Hirschi's social control theory, adolescents with stronger attachments to family, religious, academic, and other social institutions are less likely to engage in delinquent and maladaptive behavior, such as drug use leading to addiction.

Developmental stage

Adolescence represents a period of increased vulnerability to developing an addiction. In adolescence, the incentive-rewards systems in the brain mature well before the cognitive control center. This consequently grants the incentive-rewards systems disproportionate power in the behavioral decision-making process. Therefore, adolescents are increasingly likely to act on their impulses and engage in risky, potentially addictive behavior before considering the consequences. Not only are adolescents more likely to initiate and maintain drug use, but once addicted they are more resistant to treatment and more liable to relapse.

Most individuals are exposed to and use addictive drugs for the first time during their teenage years. In the United States, there were just over 2.8 million new users of illicit drugs in 2013 (7,800 new users per day); among them, 54.1% were under 18 years of age.

Adolescence is a critical developmental period in which the prefrontal cortex (responsible for planning, inhibitory control, and evaluating long-term consequences) experiences significant maturation. During this period, limbic reward circuits mature earlier than prefrontal cortex regulatory networks, creating a developmental imbalance in which reward sensitivity is high, but cognitive control is not fully developed yet. This mismatch contributes to higher experimentation with substances and vulnerability to addiction.

Neuroimaging studies show that adolescents exhibit reduced prefrontal cortex activation during decision-making tasks, risk-taking behavior, and heightened dopamine reactivity compared with adults. Exposure to substances during this early period of their life can disrupt synaptic pruning and myelination. This can produce long-term alterations in executive functioning and reward processing that increase the chance of developing a substance use disorder.

Comorbid disorders

Individuals with comorbid mental health disorders such as depression, anxiety, attention deficit hyperactivity disorder, or post-traumatic stress disorder are more likely to develop substance use disorders. The NIDA cites early aggressive behavior as a risk factor for substance use. Substance use disorders frequently co-occur with other psychiatric conditions, and current guidance recommends that comorbid psychiatric and physical conditions be treated concurrently rather than sequentially.

Psychological theories

Psychological contributions include learning and conditioning processes, impulsivity, reward sensitivity, and the use of substances to cope with negative mood or trauma. Conditioning models hold that environmental cues can acquire motivational significance of their own and trigger craving and relapse even after long periods of abstinence. Reviews of alcohol use disorder identify overvaluation of the drug's reinforcing effects, elevated impulsivity across several dimensions, the acute effects of stress and environmental triggers, and a lack of alternative rewarding activities as well-established psychological determinants. Psychological factors primarily shape how people perceive, react to, and regulate internal states. This shows how these factors influence the use of substances as coping strategies or sources of reinforcement. These processes interact with biological and social vulnerabilities, each reinforcing the others. Biological sensitivities make a person more strongly react to social challenges. These social challenges repeatedly activate and increase biological sensitivity. A cycle is created where both types of vulnerabilities keep reinforcing each other. These include: impaired inhibitory control, heightened reward drive, stress, and trauma. These interactions determine whether substance use will evolve into damaging patterns (compulsive drug seeking behaviors, loss of control of drug use, reliance on substance for coping) that are characteristic of addiction.

Personality theories

Main article: Personality theories of addiction

Personality theories of addiction are psychological models that associate personality traits or modes of thinking (i.e., affective states) with an individual's proclivity for developing an addiction. Data analysis demonstrates that psychological profiles of drug users and non-users have significant differences, and the psychological predisposition to using different drugs may be different. Models of addiction risk that have been proposed in psychology literature include: an affect dysregulation model of positive and negative psychological affects, the reinforcement sensitivity theory of impulsiveness and behavioral inhibition, and an impulsivity model of reward sensitization and impulsiveness.

Social learning theory

Main article: Social learning theory

Social learning theory, as originally proposed by Albert Bandura, holds that behavior is shaped by the reciprocal relationships between personal factors, the external environment, and the behavior itself (a principle known as reciprocal determinism). Applied to addiction, this frames drug use as arising from the interaction between an individual's personal characteristics, their social environment, and drug-related behavior itself, and characterizes addiction as a chronically evolving biopsychosocial disorder. On this account, effective treatment should target every node of the model and the relationships between them, rather than any single factor in isolation.

Evolutionary perspectives

Some scholars have proposed evolutionary explanations for addiction, suggesting that vulnerabilities to substance or behavioral dependence reflect by-products or dysregulated expressions of reward and learning systems that were adaptive in ancestral environments. Classic accounts argue that purified drugs and rapid delivery methods exploit ancient motivational circuitry by providing "false fitness signals" that mimic cues once linked to survival or reproduction. Other reviews emphasise how psychoactive substances and behavioral reinforcers act on conserved mechanisms for reward, reinforcement, and emotion, which in modern settings can be overstimulated or maladapted. These perspectives do not replace proximate neurobiological models, but aim instead to situate contemporary patterns of vulnerability within a broader evolutionary framework.

Mechanisms

Addiction develops when repeated exposure to a rewarding stimulus produces lasting changes in the brain circuits that govern reward, stress and self-control. Current accounts describe this as a recurring three-stage cycle. During binge/intoxication, dopaminergic signalling in the basal ganglia gives the drug and the cues surrounding it a powerful pull on attention and behavior. During withdrawal/negative affect, brain stress systems in the extended amygdala become overactive and ordinary pleasures become muted, so that use is increasingly driven by relief rather than reward. During preoccupation/anticipation, reduced prefrontal cortex control over these systems leaves craving poorly restrained and makes relapse more likely. Each stage is associated with persistent changes in gene expression and synaptic plasticity within the affected circuits. Due to the causal relationship between ΔFosB expression and addictions, it is used preclinically as an addiction biomarker. ΔFosB expression in these neurons directly and positively regulates drug self-administration and reward sensitization through positive reinforcement, while decreasing sensitivity to aversion.

Reward circuitry

Main article: Reward system

The reinforcing effects of most addictive drugs depend on dopamine signalling in the nucleus accumbens, the same pathway that responds to natural rewards such as food and sex. Altered dopamine neurotransmission is frequently observed following the development of an addictive state. In people and in animals that have developed an addiction, altered dopamine or opioid neurotransmission is evident in the nucleus accumbens and elsewhere in the striatum.

Cognitive and stimulus control

Cognitive control and stimulus control, which is associated with operant and classical conditioning, represent opposite processes (i.e., internal vs external or environmental, respectively) that compete over the control of an individual's elicited behaviors. Cognitive control, and particularly inhibitory control over behavior, is impaired in both addiction and attention deficit hyperactivity disorder. Stimulus-driven behavioral responses (i.e., stimulus control) that are associated with a particular rewarding stimulus tend to dominate one's behavior in an addiction.

In operant conditioning, behavior is influenced by outside stimuli, such as a drug. The operant conditioning theory of learning is useful in understanding why the mood-altering or stimulating consequences of drug use can reinforce continued use (an example of positive reinforcement) and why the addicted person seeks to avoid withdrawal through continued use (an example of negative reinforcement). Stimulus control is using the absence of the stimulus or the presence of a reward to influence the resulting behavior.

Cognitive control is the intentional selection of thoughts, behaviors, and emotions based on our environment. It has been shown that drugs alter the way our brains function and their structure. Cognitive functions such as learning, memory, and impulse control, are affected by drugs. These effects promote drug use, as well as hinder the ability to abstain from it. The increase in dopamine release is prominent in drug use, specifically in the ventral striatum and the nucleus accumbens. Dopamine is responsible for producing pleasurable feelings, as well as driving us to perform important life activities. Addictive drugs cause a significant increase in this reward system, causing a large increase in dopamine signaling as well as increase in reward-seeking behavior, in turn motivating drug use. This promotes the development of a maladaptive drug to stimulus relationship. Early drug use leads to these maladaptive associations, later affecting cognitive processes used for coping, which are needed to abstain from them successfully.

Mesocorticolimbic pathway

ΔFosB accumulation from excessive drug use

Top: this depicts the initial effects of high dose exposure to an addictive drug on gene expression in the nucleus accumbens for various Fos family proteins (i.e., c-Fos, FosB, ΔFosB, Fra1, and Fra2).
Bottom: this illustrates the progressive increase in ΔFosB expression in the nucleus accumbens following repeated twice daily drug binges, where these phosphorylated (35–37 kilodalton) ΔFosB isoforms persist in the D1-type medium spiny neurons of the nucleus accumbens for up to 2 months.

Understanding the pathways in which drugs act and how drugs can alter those pathways is key when examining the biological basis of drug addiction. The reward pathway, known as the mesolimbic pathway, or its extension, the mesocorticolimbic pathway, is characterized by the interaction of several areas of the brain.

• Dopaminergic neurons in the ventral tegmental area (VTA) fire in response to cues that predict a reward, and project to the nucleus accumbens through the mesolimbic pathway. Nearly all addictive drugs increase dopamine release along this pathway, although they act on it by different routes.
• The nucleus accumbens, made up largely of GABAergic medium spiny neurons, is a principal target of these projections. It is involved in learning conditioned responses to drug-associated cues, and in the growing sensitivity to those cues as addiction progresses.
• The prefrontal cortex, including the anterior cingulate and orbitofrontal cortices, is a further target of the mesocorticolimbic pathway. It weighs competing information in determining whether a behavior is carried out, and forms the associations between drug reward and environmental cues that give those cues their power. Importantly, these cues are strong mediators of drug-seeking behavior and can trigger relapse even after months or years of abstinence.

Other brain structures that are involved in addiction include:

• The hippocampus contributes through its role in learning and memory, and influences activity in the same dopamine pathway.

Role of dopamine and glutamate

Dopamine is the primary neurotransmitter of the brain's reward system, and also has roles in movement, emotion, cognition and motivation. Natural rewards such as eating, and recreational drug use, both trigger dopamine release, which underlies their reinforcing quality.

Excessive intake of many types of addictive drugs results in repeated release of high amounts of dopamine, which in turn affects the reward pathway directly through heightened dopamine receptor activation. Prolonged and abnormally high levels of dopamine in the synaptic cleft can induce receptor downregulation in the neural pathway. Downregulation of mesolimbic dopamine receptors can result in a decrease in the sensitivity to natural reinforcers.

Drug seeking is driven by glutamatergic projections from the prefrontal cortex to the nucleus accumbens, and chronic drug exposure produces lasting glutamate-mediated changes along this route.

Neuroadaptation and sensitization

Reward sensitization is a process that causes an increase in the amount of reward (specifically, incentive salience) that is assigned by the brain to a rewarding stimulus (e.g., a drug). In simple terms, when reward sensitization to a specific stimulus (e.g., a drug) occurs, an individual's "wanting" or desire for the stimulus itself and its associated cues increases. Reward sensitization normally occurs following chronically high levels of exposure to the stimulus.

"Cue-induced wanting" or "cue-triggered wanting", a form of craving that occurs in addiction, is responsible for most of the compulsive behavior that people with addictions exhibit. During the development of an addiction, the repeated association of otherwise neutral and even non-rewarding stimuli with drug consumption triggers an associative learning process that causes these previously neutral stimuli to act as conditioned positive reinforcers of addictive drug use (i.e., these stimuli start to function as drug cues). As conditioned positive reinforcers of drug use, these previously neutral stimuli are assigned incentive salience (which manifests as a craving) – sometimes at pathologically high levels due to reward sensitization – which can transfer to the primary reinforcer (e.g., the use of an addictive drug) with which it was originally paired.

In contrast to ΔFosB's reward-sensitizing effect, CREB transcriptional activity decreases user's sensitivity to the rewarding effects of the substance. CREB transcription in the nucleus accumbens is implicated in psychological dependence and symptoms involving a lack of pleasure or motivation during drug withdrawal.

Molecular and epigenetic mechanisms

Epigenetics is the study of stable phenotypic changes that do not involve alterations in the DNA sequence. Illicit drug use has been found to cause epigenetic changes in DNA methylation, as well as chromatin remodeling. The epigenetic state of chromatin may pose a risk for the development of substance addictions. It has been found that emotional stressors, as well as social adversities, may lead to an initial epigenetic response, which causes an alteration to the reward-signalling pathways. This change may predispose one to experience a positive response to drug use.

Altered epigenetic regulation of gene expression within the brain's reward system plays a significant and complex role in the development of drug addiction. Addictive drugs are associated with three types of epigenetic modifications within neurons. These are (1) histone modifications, (2) epigenetic methylation of DNA at CpG sites at (or adjacent to) particular genes, and (3) epigenetic downregulation or upregulation of microRNAs which have particular target genes. As an example, while hundreds of genes in the cells of the nucleus accumbens (NAc) exhibit histone modifications following drug exposure – particularly, altered acetylation and methylation states of histone residues – most other genes in the NAc cells do not show such changes.

Transgenerational

Main article: Transgenerational epigenetic inheritance

Epigenetic genes and their products (e.g., proteins) are the key components through which environmental influences can affect the genes of an individual: they serve as the mechanism responsible for transgenerational epigenetic inheritance, a phenomenon in which environmental influences on the genes of a parent can affect the associated traits and behavioral phenotypes of their offspring (e.g., behavioral responses to environmental stimuli). In addiction, epigenetic mechanisms play a central role in the pathophysiology of the disease; it has been noted that some of the alterations to the epigenome which arise through chronic exposure to addictive stimuli during an addiction can be transmitted across generations, in turn affecting the behavior of one's children (e.g., the child's behavioral responses to addictive drugs and natural rewards).

The general classes of epigenetic alterations that have been implicated in transgenerational epigenetic inheritance include DNA methylation, histone modifications, and downregulation or upregulation of microRNAs. With respect to addiction, more research is needed to determine the specific heritable epigenetic alterations that arise from various forms of addiction in humans and the corresponding behavioral phenotypes from these epigenetic alterations that occur in human offspring. Based on preclinical evidence from animal research, certain addiction-induced epigenetic alterations in rats can be transmitted from parent to offspring and produce behavioral phenotypes that decrease the offspring's risk of developing an addiction. More generally, the heritable behavioral phenotypes that are derived from addiction-induced epigenetic alterations and transmitted from parent to offspring may serve to either increase or decrease the offspring's risk of developing an addiction.

Diagnosis

Further information: Substance use disorder § Diagnosis, and Problem gambling § Diagnosis

Diagnostic criteria

DSM-5

The fifth edition of the DSM uses the term substance use disorder to refer to a spectrum of drug use-related disorders. The DSM-5 eliminates the terms abuse and dependence from diagnostic categories, instead using the specifiers of mild, moderate, and severe to indicate the extent of disordered use. The number of diagnostic criteria present in a given case determines these specifiers. In the DSM-5, the term drug addiction is synonymous with severe substance use disorder.

The DSM-5 introduced a new diagnostic category for behavioral addictions. Problem gambling is the only condition included in this category in the fifth edition. Internet gaming disorder is listed as a "condition requiring further study" in the DSM-5.

Past editions have used physical dependence and the associated withdrawal syndrome to identify an addictive state. Physical dependence occurs when the body has adjusted by incorporating the substance into its "normal" functioning – i.e., attains homeostasis – and therefore physical withdrawal symptoms occur on cessation of use. Tolerance is the process of the body adapting to a substance so that larger amounts are needed for the same effect. Withdrawal describes the physical and psychological symptoms that appear when a substance the body has adapted to is reduced or stopped. Which symptoms occur, and how dangerous they are, depends heavily on the substance: withdrawal from alcohol or benzodiazepines can be life-threatening, whereas withdrawal from most other substances is distressing but not usually dangerous.

Medical researchers who actively study addiction have criticized the DSM classification of addiction for being flawed and involving arbitrary diagnostic criteria.

ICD-11

The eleventh revision of the International Classification of Diseases, commonly referred to as ICD-11, conceptualizes diagnosis somewhat differently. ICD-11 first distinguishes between problems with psychoactive substance use ("Disorders due to substance use") and behavioral addictions ("Disorders due to addictive behaviours"). With regard to psychoactive substances, ICD-11 explains that the included substances initially produce "pleasant or appealing psychoactive effects that are rewarding and reinforcing with repeated use, [but] with continued use, many of the included substances have the capacity to produce dependence. They have the potential to cause numerous forms of harm, both to mental and physical health." Instead of the DSM-5 approach of one diagnosis ("Substance Use Disorder") covering all types of problematic substance use, ICD-11 offers three diagnostic possibilities: 1) Episode of Harmful Psychoactive Substance Use, 2) Harmful Pattern of Psychoactive Substance Use, and 3) Substance Dependence.

Screening and assessment

Screening instruments are used to identify people who may have a substance use problem and to gauge its severity, usually before a full diagnostic assessment. The World Health Organization's ASSIST covers lifetime and recent use, craving, and use-related problems across substance classes; the TAPS tool combines screening and assessment in one instrument; and the CRAFFT is designed for adolescents and includes items on substance-related driving risk. The DAST is a self-report measure of problematic drug use. Distinct from these, the Addictions Neuroclinical Assessment is a research framework that profiles people across three domains (executive function, incentive salience and negative emotionality) rather than a clinical screening questionnaire.

Prevention

Main article: Preventive healthcare

Because many risk factors for addiction are social and modifiable, prevention strategies that target them can improve outcomes; when delivered during childhood and adolescence, such strategies reduce the risk of later substance use disorder. Prevention is usually organized in three tiers: universal programs aimed at a whole population, selective programs aimed at groups at raised risk, and indicated programs aimed at individuals already showing early signs of problem use. Interventions with the strongest evidence include family skills programs, personal and social skills education delivered in schools, and policies that limit availability and raise the price of alcohol and tobacco. Programs based on information provision alone, or on fear-based messaging, have not been found effective and may be counterproductive.

Management

Main article: Treatment and management of addiction

Addiction is generally managed as a chronic, relapsing condition rather than something resolved in a single episode of care. The most effective treatment combines medication (where an effective one is available) with psychological and social support, emphasising long-term management and relapse prevention. To be effective, pharmacological or biologically based treatment needs to be accompanied by other interventions such as cognitive behavioral therapy (CBT) and dialectical behavioral therapy (DBT), individual and group psychotherapy, behavior modification strategies, twelve-step programs, and residential treatment facilities.

Pharmacological

The medications available differ between substances. For opioid use disorder, opioid agonist maintenance treatment with methadone or buprenorphine is common. It retains people in treatment and suppresses illicit opioid use more effectively than no opioid replacement, and is associated with reduced mortality and lower transmission of blood-borne infections such as HIV and hepatitis C. The opioid antagonist naltrexone is an alternative for some patients. For alcohol use disorder, oral naltrexone and acamprosate are recommended as first-line medications alongside psychosocial support, whereas trial evidence that disulfiram reduces drinking is weaker. For tobacco (nicotine) dependence, varenicline, cytisine and nicotine e-cigarettes are among the most effective aids for quitting long-term, followed closely by using two forms of nicotine replacement therapy at once (for example a patch together with gum or a lozenge), bupropion is also used. No medication has been approved for cocaine or amphetamine (stimulant) use disorder, for which psychosocial treatment remains the principal care.

Psychological and behavioral

Psychological and behavioral therapies are used across all forms of addiction, both alone and together with medication; commonly used approaches include CBT, motivational interviewing, contingency management (which provides tangible rewards for verified abstinence), and twelve-step facilitation. For stimulant use disorder, contingency management (particularly when combined with a community reinforcement approach) has the strongest supporting evidence among psychosocial treatments. For alcohol use disorder, structured twelve-step facilitation programmes that encourage participation in Alcoholics Anonymous are at least as effective as other established therapies such as CBT for sustaining abstinence and may lower health-care costs. The transtheoretical model (TTM) can help determine when treatment should begin and which method is likely to be most effective, as beginning too early may make a person defensive and resistant to change.

Transtheoretical model (stages of change model)

Main article: Transtheoretical model

The transtheoretical model describes behavior change as a stepwise progression through a series of stages (precontemplation, contemplation, preparation, action and maintenance) through which people commonly move back and forth rather than in a single linear sequence, with relapse treated as an expected part of the process rather than a failure. In addiction treatment the model is used to gauge a person's readiness to change and to time intervention accordingly, since beginning too early may make a person defensive and resistant to change.

Harm reduction

Main article: Harm reduction

Harm reduction covers measures that reduce the damage associated with continued substance use rather than requiring abstinence. Approaches include needle and syringe programmes, naloxone distribution to reverse opioid overdose, drug checking, and supervised consumption facilities. Opioid agonist maintenance treatment also functions as harm reduction: independently of whether use stops, it is associated with reduced mortality and lower transmission of blood-borne infections.

Prognosis

Addiction is generally understood as a chronic, relapsing condition rather than one resolved in a single episode of care, and long-term outcomes vary widely. A systematic review and meta-analysis of long-term follow-up studies estimated that between 35% and 54% of people with a substance use disorder achieved remission (defined as no longer meeting diagnostic criteria for at least six months) but that this typically occurred only after a mean follow-up of around 17 years, with roughly 7–9% of cases remitting in any given year. Its authors concluded that for a substantial proportion of people the condition behaves more like a long-term than an acute disorder, and argued for treatment models designed around chronicity. Substance use disorders are treatable: there is evidence of clinically significant benefit for medications in opioid, nicotine and alcohol use disorders, for behavioral therapies across all substance use disorders, and for neuromodulation in nicotine use disorder.

Epidemiology

Further information: Countries by alcohol consumption, Opioid epidemic, and Prevalence of tobacco use

Due to cultural variations, the proportion of individuals who develop a drug or behavioral addiction within a specified time period (i.e., the prevalence) varies over time, by country, and across national population demographics (e.g., by age group, socioeconomic status, etc.). The Global Burden of Disease Study estimated that in 2016 alcohol use disorders were the most prevalent substance use disorder worldwide, with about 100 million cases, followed by opioid dependence at about 27 million and cannabis dependence at about 22 million. In the same year, alcohol use as a risk factor accounted for an estimated 99.2 million disability-adjusted life years (DALYs), or 4.2% of the global total, and drug use for 31.8 million DALYs, or 1.3%. Alcohol-attributable burden was heaviest in countries with a low Socio-demographic Index, whereas drug-attributable burden increased with higher socio-demographic development. Between 2010 and 2023, drug use was one of only three risk factors worldwide whose age-standardised attributable DALY rate rose.

Regional variation

Patterns differ markedly by region. Alcohol-attributable burden falls most heavily on countries with a low Socio-demographic Index, whereas drug-attributable burden rises with higher socio-demographic development. In Europe, mortality from alcohol and illicit drugs is highest in the east of the continent, and first alcohol use before age 13 was reported for 28% of European children in 2014. Alcohol dependence is less prevalent across much of Asia than in Western countries, reflecting both socioeconomic and biological differences in drinking behavior. In Latin America, heroin consumption is low in most countries despite regional opium production, with the highest incidence in Mexico.

History

Modern research on addiction has led to a better understanding of the disease with research on the topic dating back to 1875, specifically on morphine addiction. This furthered the understanding of addiction being a medical condition. It was not until the 19th century that addiction was seen and acknowledged in the Western world as a disease, being both a physical condition and mental illness. Today, addiction is understood both as a biopsychosocial and neurological disorder that negatively impacts those who are affected by it, most commonly associated with the use of drugs and excessive use of alcohol.

Terminology

The word addiction derives from the Latin "addico", meaning "giving over" with both positive connotations (devotion, dedication) and negative ones (being enslaved to a creditor in Roman law). This dual meaning persisted in traditional English dictionaries, encompassing both legal surrender and personal devotion to habits. Later, the 19th century temperance movements narrowed the definition of addiction to just drug-related disease, ignoring behavioral addictions and the possibility of positive or neutral addictions. This restrictive view opposes the current understanding of addiction.

Addiction and addictive behavior are polysemes denoting a category of mental disorders, of neuropsychological symptoms, or of merely maladaptive/harmful habits and lifestyles. A common use of the term addiction in medicine is for neuropsychological symptoms denoting pervasive/excessive and intense urges to engage in a category of behavioral compulsions or impulses towards sensory rewards (e.g., alcohol, betel quid, drugs, sex, gambling, video gaming). Addictive disorders or addiction disorders are mental disorders involving high intensities of addictions (as neuropsychological symptoms) that induce functional disabilities (i.e., limit subjects' social/family and occupational activities); the two categories of such disorders are substance-use addictions and behavioral addictions.

The etymology of the term addiction throughout history has been misunderstood and has taken on various meanings associated with the word. An example is the usage of the word in the religious landscape of early modern Europe. "Addiction" at the time meant "to attach" to something, giving it both positive and negative connotations. The object of this attachment could be characterized as "good or bad". The meaning of addiction during the early modern period was mostly associated with positivity and goodness; during this early modern and highly religious era of Christian revivalism and Pietistic tendencies, it was seen as a way of "devoting oneself to another".

The suffixes "-holic" and "-holism"

In contemporary English, "-holic" is a suffix that can be added to a subject to denote an addiction to it. It was extracted from the word alcoholism (one of the first addictions to be widely identified both medically and socially) (correctly the root "alcohol" plus the suffix "-ism") by misdividing or rebracketing it into "alco" and "-holism". Terms formed this way, such as chocoholic and workaholic, are colloquial rather than diagnostic; the only behavioral addictions recognised in current diagnostic manuals are gambling disorder and gaming disorder.

Society and culture

Economic and social cost

Addiction causes an "astoundingly high financial and human toll" on individuals and society as a whole. In the United States, the total economic cost to society is greater than that of all types of diabetes and all cancers combined. These costs arise from the direct adverse effects of drugs and associated healthcare costs (e.g., emergency medical services and outpatient and inpatient care), long-term complications (e.g., lung cancer from smoking tobacco products, liver cirrhosis and dementia from chronic alcohol consumption, and meth mouth from methamphetamine use), the loss of productivity and associated welfare costs, fatal and non-fatal accidents (e.g., traffic collisions), suicides, homicides, and incarceration, among others. The US National Institute on Drug Abuse has found that overdose deaths in the US have almost tripled among males and females from 2002 to 2017, with 72,306 overdose deaths reported in 2017 in the US. 2020 marked the year with the highest number of overdose deaths over a 12-month period, with 81,000 overdose deaths, exceeding the records set in 2017.

Structural and political accounts

Emerging in the early 1980s, the critical medical anthropology model was introduced, and as Merrill Singer offers 'was applied quickly to the analysis of drug use'. Where the cultural model of the 1950s looked at the social body, the critical medical anthropology model revealed the body politic, considering drug use and addiction within the context of macro level structures including larger political systems, economic inequalities, and the institutional power held over social processes.

Highly relevant to addiction, the three issues emphasized in the model are:

• Self-medication
• The social production of suffering
• The political economy (Licit and Illicit Drugs)

These three key points highlight how drugs may come to be used to self-medicate the psychological trauma of socio-political disparity and injustice, intertwining with licit and illicit drug market politics. Social suffering, "the misery among those on the weaker end of power relations in terms of physical health, mental health and lived experience", is used by anthropologists to analyze how individuals may have personal problems caused by political and economic power. From the perspective of critical medical anthropology, heavy drug use and addiction are consequences of such larger-scale unequal distributions of power.

Cultural and anthropological accounts

Cultural model

The cultural model, an anthropological understanding of the emergence of drug use and abuse, was developed by Dwight Heath. Heath undertook ethnographic research and fieldwork with the Camba people of Bolivia from June 1956 to August 1957. Heath observed that adult members of society drank 'large quantities of rum and became intoxicated for several contiguous days at least twice a month'. This frequent, heavy drinking from which intoxication followed was typically undertaken socially, during festivals. Having returned in 1989, Heath observed that while much had changed, 'drinking parties' remained, as per his initial observations, and 'there appear to be no harmful consequences to anyone'. Heath's observations and interactions reflected that this form of social behavior, the habitual heavy consumption of alcohol, was encouraged and valued, enforcing social bonds in the Camba community. Despite frequent intoxication, "even to the point of unconsciousness", the Camba held no concept of alcoholism (a form of addiction), and no visible social problems associated with drunkenness, or addiction, were apparent.

As noted by Merrill Singer, Heath's findings, when considered alongside subsequent cross-cultural experiences, challenged the perception that intoxication is socially 'inherently disruptive'. Following this fieldwork, Heath proposed the 'cultural model', suggesting that 'problems' associated with heavy drinking, such as alcoholism – a recognised form of addiction – were cultural: that is, that alcoholism is determined by cultural beliefs, and therefore varies among cultures. Heath's findings challenged the notion that 'continued use [of alcohol] is inexorably addictive and damaging to the consumer's health'.

The cultural model did face criticism by Sociologist Robin Room and others, who felt anthropologists could "downgrade the severity of the problem". Merrill Singer found it notable that the ethnographers working within the prominence of the cultural model were part of the 'wet generation': while not blind to the 'disruptive, dysfunctional and debilitating effects of alcohol consumption', they were products 'socialized to view alcohol consumption as normal'.

Subcultural model

Historically, addiction has been viewed from the etic perspective, defining users through the pathology of their condition. As reports of drug use rapidly increased, the cultural model found application in anthropological research exploring western drug subculture practices.

The approach evolved from the ethnographic exploration into the lived experiences and subjectivities of 1960s and 70s drug subcultures. The seminal publication "Taking care of business", by Edward Preble and John J. Casey, documented the daily lives of New York street-based intravenous heroin users in detail, providing insight into the dynamic social worlds and activities that surrounded their drug use. These findings challenge popular narratives of immorality and deviance, conceptualizing substance use as a social phenomenon. The prevailing culture can influence drug-taking behaviors, along with the physical and psychological effects of the drug. To marginalized individuals, drug subcultures can provide social connection, symbolic meaning, and socially constructed purpose that they may feel is unattainable through conventional means. The subcultural model demonstrates the complexities of addiction, highlighting the need for an integrated approach. It contends that a biosocial approach is required to achieve a holistic understanding of addiction.

Addiction in art

The creative arts therapies (including art therapy, music therapy, drama and dance) are sometimes used as complementary treatments for substance use disorders, generally alongside conventional therapy. Artwork produced during treatment has also been used as an informal aid to assessment and to tracking progress. Proposed benefits include offering a non-verbal outlet for difficult emotions, containing shame, and strengthening self-awareness and engagement in treatment. However, a 2018 systematic review found insufficient evidence to confirm that visual art, drama, or dance and movement therapies reduce substance misuse, although music therapy showed some promise in preparing people for treatment.

The arts are used in advocacy and public education about addiction. Artists (particularly those with lived experience of addiction and recovery) use their work to reduce stigma and to reframe addiction as a treatable health condition rather than a moral failing, an approach intended to promote public compassion and shift responses from the criminal-justice system toward the public-health system.

Research directions

Vaccines intended to reduce the effects of addictive drugs have been investigated since the early 2000s. The approach conjugates the drug molecule to a carrier protein so that the immune system produces antibodies that bind the drug in the bloodstream, reducing the amount that reaches the brain. Candidates have been tested against nicotine, cocaine, opioids and fentanyl.

No such vaccine is licensed for use in any country. A Cochrane review found no evidence that nicotine vaccines improve long-term smoking cessation, and two phase III trials of NicVAX reported quit rates of approximately 11% in both the vaccine and the placebo groups. Anti-cocaine vaccine development has likewise not produced an approved product, and no pharmacological treatment for cocaine dependence is currently approved.

GLP-1 receptor agonist medications such as semaglutide, developed for type 2 diabetes and obesity, have attracted interest as possible treatments for substance use disorders because they act on the brain's reward system and reduce reward-driven behavior. Large observational studies have associated their use with lower rates of alcohol- and opioid-related harm; however, the small number of completed randomized controlled trials has not yet confirmed a consistent benefit, and specialists currently describe these medications as promising but unproven for this indication.

See also

• Autonomic nervous system
• Binge drinking
• Binge eating disorder
• Cognitive liberty
• Darwinian hedonism
• Discrimination against drug addicts
• Dopaminergic pathways
• Pavlovian-instrumental transfer
• Philosophy of medicine
• Substance dependence

Notes

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Further reading

• Pelchat ML (March 2009). "Food Addiction in Humans". The Journal of Nutrition. 139 (3): 620–622. doi:10.3945/jn.108.097816. PMID 19176747.
• Gordon HW (April 2016). "Laterality of Brain Activation for Risk Factors of Addiction". Current Drug Abuse Reviews. 9 (1): 1–18. doi:10.2174/1874473709666151217121309. PMC 4811731. PMID 26674074.
• Szalavitz M (2016). Unbroken Brain. St. Martin's Press. ISBN 978-1-250-05582-8.
• Courtwright DT (2019). The Age of Addiction: How Bad Habits Became Big Business. Cambridge, Massachusetts: Harvard University Press. ISBN 978-0-674-24822-9.

External links

• "The Science of Addiction: Genetics and the Brain". learn.genetics.utah.edu. Learn.Genetics – University of Utah.
• Why do our brains get addicted? – a TEDMED 2014 talk by Nora Volkow, the director of the National Institute on Drug Abuse at NIH.

Kyoto Encyclopedia of Genes and Genomes (KEGG) signal transduction pathways:

• KEGG – human alcohol addiction
• KEGG – human amphetamine addiction
• KEGG – human cocaine addiction