Drug Abuse and Substance Use Disorder

How drug use becomes a disorder

Drugs act on the brain's reward circuit by releasing large amounts of dopamine, far more than natural rewards such as food or social contact. With repeated use the brain adapts:

• Tolerance: the same dose has less effect, so more is used.
• Dependence: the body adapts to the drug, so stopping causes withdrawal.
• Craving and habit: cues linked to the drug (people, places, stress) trigger strong urges.
• Weakened self-control: the prefrontal cortex, which handles planning and impulse control, works less well.

These changes explain why people keep using despite clear harm, and why willpower alone often fails. Physical dependence can occur with prescribed medicines taken correctly; that alone is not a substance use disorder.

Symptoms and diagnostic criteria

Doctors use the DSM-5-TR criteria. Over 12 months:

2 to 3 criteria = mild, 4 to 5 = moderate, 6 or more = severe. For practical signs that family and friends notice, see signs of drug abuse.

Causes and risk factors

• Genetics: inherited factors account for roughly 40 to 60% of addiction risk.
• Early use: the teenage brain is still developing, and earlier first use raises the risk of later disorder.
• Mental health: depression, anxiety, ADHD, bipolar disorder, schizophrenia and PTSD often co-occur. Each can worsen the other.
• Trauma and adversity: childhood abuse, neglect and household dysfunction.
• Chronic pain and long-term opioid prescribing.
• Environment: availability of drugs, peer use, poverty and social isolation.
• The drug itself: fast-acting routes (smoking, injecting) and potent drugs such as fentanyl and methamphetamine lead to disorder faster.

Types by substance

• Opioids: heroin, fentanyl, prescription painkillers. Highest overdose risk. See opioid use disorder.
• Stimulants: cocaine, methamphetamine, misused ADHD medicines. See stimulant use disorder.
• Sedatives: benzodiazepines and barbiturates. Dangerous withdrawal.
• Cannabis: cannabis use disorder affects a minority of users, more often with daily or high-potency use.
• Alcohol: the most common, and often combined with other drugs. See alcohol use disorder.
• Hallucinogens, inhalants and others.

Health effects and complications

• Overdose: a leading cause of injury death in US adults in recent years, driven mainly by illicit fentanyl.
• Infections: HIV, hepatitis B and C, heart valve infection (endocarditis), skin abscesses from injecting.
• Heart and lungs: heart attack, stroke and heart rhythm problems with stimulants; lung damage from smoking.
• Brain and mental health: psychosis, depression, anxiety, memory problems.
• Liver and kidneys: from drugs, alcohol and infections.
• Pregnancy: miscarriage, low birth weight and neonatal withdrawal syndrome.
• Social: job loss, debt, housing instability, legal problems and family breakdown.

Diagnosis

There is no blood test for addiction. A doctor makes the diagnosis by asking about substance use, its effects and the 11 criteria, often using validated screening questions. Urine or blood drug tests can confirm recent use but cannot show whether someone has a disorder. Assessment also covers mental health, physical health (including tests for HIV, hepatitis and liver function), pregnancy and social needs such as housing and safety.

Treatment

Treatment is tailored to the substance, severity and the person's goals. Combining approaches works best.

Medications

• Opioid use disorder: buprenorphine, methadone and extended-release naltrexone. These reduce cravings and withdrawal and cut the risk of overdose death substantially. They are effective long-term treatments, not "replacing one drug with another".
• Alcohol use disorder: naltrexone, acamprosate, disulfiram.
• Tobacco: nicotine replacement, varenicline, bupropion.
• Stimulants and cannabis: no FDA-approved medicines yet; behavioral therapies are the mainstay.
• Naloxone for anyone at risk of opioid overdose, and for their families.

Supervised withdrawal

Withdrawal from alcohol, benzodiazepines and barbiturates can be life-threatening and should be managed medically. Opioid withdrawal is rarely dangerous but very unpleasant, and is best managed by starting buprenorphine or methadone. See drug withdrawal.

Behavioral therapies

• Cognitive behavioral therapy to recognize triggers and build coping skills
• Contingency management: small rewards for drug-free tests, the most effective therapy for stimulant use
• Motivational interviewing to strengthen readiness to change
• Family therapy, especially for adolescents

Support and harm reduction

Peer support (Narcotics Anonymous, SMART Recovery), recovery coaches, sober living housing, syringe services programs, fentanyl test strips and treatment of co-occurring mental health conditions all reduce harm and support recovery.

Outlook

Substance use disorder is a chronic condition with relapse rates similar to other chronic illnesses such as asthma and high blood pressure. Relapse does not mean treatment failed; it means treatment needs adjusting. Many people achieve lasting recovery, especially with medication, continued support and stable housing and work.

Prevention

• Delay the age of first use and talk openly with teenagers about drugs.
• Store prescription medicines securely and dispose of unused ones at take-back sites.
• Treat depression, anxiety, ADHD and trauma early.
• Use opioids for pain only as prescribed and for the shortest time needed.

Frequently asked questions

What is the medical term for drug abuse?

The current medical term is substance use disorder, named for the specific drug, for example opioid use disorder or stimulant use disorder. It replaced the older categories of "substance abuse" and "substance dependence" in 2013 and is graded mild, moderate or severe.

What causes drug abuse?

No single cause. Genetics account for about half of the risk. Early first use, trauma, mental health conditions, chronic pain, peer and family drug use, and easy access to drugs add to it. Repeated use then changes brain circuits for reward and self-control.

Can substance use disorder be cured?

It is usually managed rather than cured, like other chronic conditions. With treatment, many people stop using or greatly reduce harm and live healthy lives. Medications for opioid and alcohol use disorders significantly improve outcomes and reduce deaths.

What is the most effective treatment for drug addiction?

For opioid use disorder, medication with buprenorphine or methadone is the most effective treatment and cuts overdose deaths. For stimulants, contingency management works best. Combining medication where available with therapy and peer support gives the best results.

Is it safe to quit drugs cold turkey?

It depends on the drug. Stopping alcohol, benzodiazepines or barbiturates suddenly after heavy use can cause seizures and be fatal. Quitting opioids abruptly is not usually dangerous by itself, but it raises overdose risk if you relapse because tolerance falls. Get medical advice first.