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Addiction and substance use disorders
· Condition or disorder
Well replicatedStrong, repeated evidence.
Compulsive use of alcohol or drugs that continues despite clear harm, with craving and loss of control.
See it on the Psychology map →What it says
DSM-5 (2013) merged 'abuse' and 'dependence' into one substance use disorder, rated mild to severe across 11 criteria such as craving, tolerance, failed attempts to cut back and giving up important activities. In 2023 about 48 million Americans aged 12 and older met criteria. US overdose deaths topped 100,000 a year in 2021–23 before falling in 2024. Methadone and buprenorphine roughly halve the risk of death in opioid addiction; therapy and mutual-help groups also help. Many, likely most, eventually recover.
Why it matters
Seeing addiction as a treatable condition rather than a moral failing changed policy and care. It shows how reward learning can be turned against a person's own goals.
The evidence
National surveys (NSDUH), CDC death records, twin studies putting heritability near 50 percent, brain imaging of reward circuits, and controlled trials of medications.
Open questions
Whether addiction is best called a 'brain disease' or a learned pattern of choice is debated, as is why only a minority of users become addicted.
Inside this (1)
Connections (5)
▸Dopamine, reward and prediction error is hijacked in Addiction and substance use disordersWell replicated
The connection
Cocaine, amphetamine, opioids, alcohol and nicotine all raise dopamine in the brain's reward circuit, often far more than food or sex. That surge acts as a powerful teaching signal, stamping in cues and habits so craving grows, while repeated use dulls the response to everyday rewards.
Who showed it and when
Gaetano Di Chiara showed in 1988 that most abused drugs raise dopamine in rats; Nora Volkow's brain scans from the 1990s found fewer dopamine receptors in people with addiction.
The evidence
Animal studies, human brain imaging and reward-prediction research converge; blocking dopamine reduces drug-seeking in animals.
Open questions
'Hijacking' simplifies: dopamine drives wanting more than pleasure, and why only some users become addicted points to genes, stress and environment too.
▸Habits and habit formation can harden into Addiction and substance use disordersMixed evidence
The connection
Repeated drug use may shift control of behavior from goal-directed brain circuits, which weigh consequences, toward habit circuits in the dorsal striatum, which respond automatically to cues. Use that began as a choice for pleasure can become a cue-triggered routine that runs even when the person no longer wants it.
Who showed it and when
Proposed by Barry Everitt and Trevor Robbins at Cambridge in 2005, building on rat studies of how habits form with repeated reward.
How solid is it?
Rats with long drug histories keep seeking drugs even when punished, and imaging suggests a shift toward the dorsal striatum, but human evidence is mixed.
Open questions
Some researchers argue people with addiction remain largely goal-directed and that compulsion is overstated; how much habit explains relapse is debated.
▸Present bias (hyperbolic discounting) is steep in Addiction and substance use disordersWell replicated
The connection
People with addictions discount future rewards much more steeply than others: in choice tasks they more often take a small amount now over a larger amount later. That steep present bias helps explain why the immediate high wins out over long-term health, money and relationships.
Who showed it and when
Warren Bickel and colleagues found steep discounting in opioid users in the late 1990s; similar results followed for alcohol, nicotine, cocaine and gambling.
The evidence
Meta-analyses in 2011 and 2017 confirmed steeper discounting across many substance use disorders; in some studies it also predicts relapse.
Open questions
Whether steep discounting comes before drug use, results from it, or both is unsettled; there is evidence for each direction.
▸Addiction and substance use disorders are a major group of Mental disorders: what they are and how commonWell replicated
The connection
Substance use disorders are among the most common mental disorders, affecting about one in six Americans aged 12 and older in a given year. They often occur alongside depression, anxiety, PTSD and ADHD, and having one raises the risk of the other.
Who showed it and when
The US National Survey on Drug Use and Health (begun in 1971, yearly since 1990, now run by SAMHSA) and the Epidemiologic Catchment Area study of the 1980s.
The evidence
Large surveys consistently find that roughly half of people with a substance use disorder also have another mental disorder.
Open questions
Which comes first, mental illness leading to self-medication or substance use causing mental illness, varies by person and is hard to untangle.
▸Gambling disorder was the first behavior added to Addiction and substance use disordersWell replicated
The connection
Gambling disorder shares the hallmarks of drug addiction: tolerance (bigger bets), withdrawal-like restlessness, failed attempts to stop, craving and the same reward circuitry. In 2013 DSM-5 moved it from the impulse-control disorders into the addiction chapter, the only behavior placed there.
Who showed it and when
DSM-5 work group, 2013; 'internet gaming disorder' was listed only for further study, while the WHO added gaming disorder to ICD-11 in 2019.
The evidence
Brain imaging, genetic overlap and treatment studies, including some benefit from naltrexone, an opioid-blocking addiction drug, support the grouping.
Open questions
Whether other compulsive behaviors, such as shopping, sex or social media, are true addictions or ordinary habits labeled as illness remains contested.