Psychology of Addiction: Understanding Substance Use Disorders

What Is Addiction?

Addiction is a pattern of compulsive substance use (or, in some cases, behavior) that continues despite clear harm to a person's health, relationships, work or wellbeing. In clinical terms the DSM-5-TR calls it substance use disorder, rated as mild, moderate or severe. The psychology of addiction asks why this happens: why people lose control over something they once chose freely, why cravings return years later, and what helps people change.

The DSM-5-TR describes eleven criteria grouped into four areas: impaired control (using more than intended, unsuccessful efforts to cut down, craving), social impairment (failing to meet obligations, giving up activities, continued use despite relationship problems), risky use (use in dangerous situations or despite known physical or psychological harm), and pharmacological criteria (tolerance and withdrawal). These criteria guide professional assessment rather than self-diagnosis.

For a broad overview of the different types of addiction and where to get help, see our main addiction page. This page focuses on the psychological theories and research behind addiction and recovery.

Brain Changes in Addiction

The reward system

The brain's reward circuits, which involve the neurotransmitter dopamine and regions such as the ventral striatum, evolved to reinforce behaviors important for survival, such as eating and social bonding. Many addictive substances trigger a larger and faster dopamine response in these circuits than natural rewards do, which strengthens learning about the substance and the cues around it. This is one reason substances can come to dominate motivation.

Adaptation, stress and self-control

With repeated use, the brain adapts. Neuroscientists such as Nora Volkow and George Koob have described three overlapping stages: binge or intoxication, driven by reward; withdrawal and negative affect, in which stress systems become more active and ordinary pleasures feel blunted; and preoccupation or anticipation, marked by craving and weakened control by the prefrontal cortex, the region involved in planning and impulse control. Over time, many people describe using less to feel good and more to avoid feeling bad.

Wanting versus liking

In 1993, psychologists Terry Robinson and Kent Berridge proposed the incentive-sensitization theory. They argued that repeated use makes the brain's "wanting" system hypersensitive to drug cues, even while "liking" (the actual pleasure) stays the same or declines. This helps explain a puzzling feature of addiction: people can intensely crave a substance they no longer enjoy. The theory has substantial support from animal and human studies.

Many of these brain changes can improve with sustained recovery, though some cue-related learning appears long-lasting, which helps explain why relapse risk can persist. See our page on neuroplasticity for more on how the brain changes with experience.

Psychological Mechanisms

Neuroscience explains part of the picture. Classic learning theories explain much of the rest, and they underpin many effective treatments.

Classical conditioning and cue reactivity

Through classical conditioning, places, people, objects, times of day and moods that have repeatedly been paired with use become cues that trigger craving automatically. Laboratory studies show that simply seeing drug-related images can raise heart rate and craving in people with substance use disorders. This is why returning to an old neighbourhood or feeling a familiar kind of stress can be so risky in early recovery.

Operant conditioning and negative reinforcement

In operant conditioning, behaviors followed by rewards become more frequent. Early on, positive reinforcement (a pleasant effect) may dominate. Later, negative reinforcement often takes over: using relieves withdrawal, anxiety, loneliness or painful memories, so use is strengthened even as overall life gets worse. Immediate relief tends to outweigh delayed harm, a pattern behavioral economists call delay discounting.

Social learning and expectancies

Albert Bandura's social learning theory highlights how people learn substance use patterns by watching family, friends and media. People also develop expectancies, beliefs about what a substance will do for them, such as making them more confident or relaxed. Research shows these expectancies predict later drinking and drug use, independently of the actual effects.

Coping, self-medication and thinking patterns

The self-medication hypothesis, associated with psychiatrist Edward Khantzian, proposes that some people use substances to manage painful emotional states. Thinking patterns such as minimising ("it's not that bad"), rationalising and denial can protect continued use from change. Shame can also keep the cycle going, because it pushes people toward secrecy and isolation rather than help.

Major Models of Addiction

Over the past century, addiction has been explained in very different ways. Each model has influenced how society responds.

The brain disease debate

The U.S. National Institute on Drug Abuse and many medical bodies describe addiction as a chronic, relapsing brain condition, a view summarised by Volkow, Koob and McLellan in 2016. Supporters argue the model reduces stigma and supports medical care.

Critics such as psychologist Gene Heyman and neuroscientist Marc Lewis argue that the evidence is more mixed. They point out that most people who meet criteria for addiction eventually stop, often without treatment, and that use responds to incentives and life changes. A classic study by Lee Robins and colleagues (1974) found that most U.S. soldiers who had become dependent on heroin in Vietnam did not resume dependent use after returning home, suggesting environment plays a huge role. Bruce Alexander's "Rat Park" experiments in the late 1970s suggested that rats in enriched social environments consumed less morphine than isolated rats, though attempts to replicate them have had mixed results. Many researchers now favour a middle position in which brain changes are real but interact with context and choice.

Risk Factors and Vulnerability

Most people who try alcohol or other drugs do not develop a substance use disorder. Vulnerability reflects several interacting influences:

• Genetics: twin and adoption studies suggest that roughly 40–60% of the variation in addiction risk is heritable. Genes influence how strongly substances are experienced, how the body processes them, and traits such as impulsivity.
• Age of first use: starting in adolescence is associated with higher risk, possibly because the brain's control systems are still developing. See adolescent psychology.
• Early adversity and trauma: adverse childhood experiences are strongly associated with later substance problems. See childhood trauma.
• Mental health conditions: depression, anxiety, PTSD and ADHD commonly co-occur with substance use disorders.
• Social environment: peer use, family patterns, availability, poverty and isolation all play roles.

Protective factors include supportive relationships, stable housing and employment, engagement in school or meaningful work, effective coping skills and community connection. Prevention programs target these factors as well as risks.

Behavioral Addictions

Psychologists increasingly study whether behaviors can become addictive in the same way as substances. The DSM-5-TR includes gambling disorder in its substance-related and addictive disorders chapter, based on evidence of similar craving, tolerance-like escalation, loss of control and brain reward patterns. Internet gaming disorder is listed for further study, and ICD-11 recognises gaming disorder. Other proposed behavioral addictions, such as compulsive buying, workaholism and food addiction, remain more debated. Critics warn against labelling every enthusiastic activity as an addiction, while supporters point to genuine suffering in severe cases. See gaming addiction for one detailed example.

Treatment Approaches

Effective treatment usually addresses biological, psychological and social factors together. Care is matched to severity and individual needs, ranging from brief advice in primary care to outpatient therapy and residential programs.

Psychological therapies

• Cognitive behavioral therapy: helps people identify triggers, build coping skills, challenge unhelpful beliefs and plan for high-risk situations. It has broad research support across substances.
• Motivational interviewing: developed by William Miller and Stephen Rollnick, it is a collaborative conversation style that helps people resolve ambivalence about change. It is often used as a first step.
• Contingency management: provides tangible rewards, such as vouchers, for verified abstinence or treatment goals. Based on operant principles, it has some of the strongest evidence for stimulant use disorders.
• Family and couples approaches: involve loved ones, improve communication and can increase treatment engagement.
• Mutual-support groups: twelve-step groups and alternatives such as SMART Recovery offer peer support; research suggests that active involvement is associated with better outcomes for many people.

Medical care

For some substance use disorders, particularly involving opioids, alcohol and tobacco, medications have strong research support, especially combined with psychological support. Medically supervised withdrawal may be needed for some substances, because stopping suddenly can be dangerous. Decisions about medication or withdrawal management should always be made with a doctor.

Stages of change

James Prochaska and Carlo DiClemente's transtheoretical model (1983) describes change as moving through stages: precontemplation, contemplation, preparation, action and maintenance. The model is widely used to match interventions to a person's readiness, though researchers debate whether people really move through discrete stages.

Recovery and Relapse

Recovery is usually understood as more than stopping use: it involves building a satisfying life in which substances no longer play a central role. Large surveys suggest that many people who once met criteria for a substance use disorder eventually achieve remission, often after several attempts. Rebuilding relationships, purpose, health and identity are all part of the process.

Relapse is common, with rates comparable to other chronic conditions such as hypertension and asthma, so it is generally treated as information rather than failure. G. Alan Marlatt's relapse prevention model (developed with Judith Gordon in 1985) identifies high-risk situations, such as negative emotions, interpersonal conflict and social pressure, and teaches specific coping responses. Marlatt also described the abstinence violation effect: after a single lapse, thinking "I've blown it" can turn a slip into a full relapse. Learning to respond to lapses with problem-solving rather than self-blame is a core skill. Mindfulness-based relapse prevention and urge surfing build on this approach.

Harm Reduction and Public Health

Harm reduction aims to reduce the health and social harms of substance use for people who are not ready or able to stop. It sits alongside abstinence-focused treatment rather than replacing it. Examples include syringe service programs to prevent HIV and hepatitis transmission, wide distribution of overdose-reversal medication, and low-barrier access to treatment.

Critics have argued that harm reduction might encourage use. Research reviews generally find that well-run programs reduce disease transmission and deaths without increasing use, and they can act as a bridge into treatment. Public health approaches also include prevention in schools and communities, reducing stigma, and addressing social conditions such as poverty, housing and isolation that make addiction more likely.

Getting Help

If substance use is causing problems for you or someone you care about, talking with a primary care doctor or a mental health professional is a useful first step. In the United States, the SAMHSA National Helpline offers free, confidential treatment referral. Our guide to supporting someone covers how to help a loved one, and crisis resources lists immediate help if someone is in danger.