Psychoactive drug

A psychoactive drug, psychopharmaceutical, mind-altering drug, consciousness-altering drug, psychoactive substance, or psychotropic substance is a chemical substance that alters psychological functioning by modulating central nervous system (CNS) activity. Psychoactive and psychotropic drugs both affect the brain, with psychotropics sometimes referring to psychiatric drugs or high-abuse substances. Novel psychoactive substances are designer drugs made to mimic illegal ones and bypass laws.

Psychoactive drug use dates back to prehistory for medicinal, recreational, or religious purposes, with evidence of widespread cultural use. Many animals intentionally consume psychoactive substances, and some traditional legends suggest animals first introduced humans to their use. Psychoactive substances are used across cultures for purposes ranging from medicinal and therapeutic treatment of mental disorders and pain, to performance enhancement. Their effects are influenced by the drug itself, the environment, and individual factors. Psychoactive drugs are categorized by their pharmacological effects into types such as anxiolytics (reduce anxiety), entactogens (enhance empathy), stimulants (increase CNS activity), depressants (decrease CNS activity), and hallucinogens (alter perception and emotions). Psychoactive drugs are administered through various routes—including oral ingestion, injection, rectal use, and inhalation—with the method and efficiency differing by drug.

Psychoactive drugs alter brain function by interacting with neurotransmitter systems—either enhancing or inhibiting activity—which can affect mood, perception, cognition, behavior, and potentially lead to dependence or long-term neural adaptations such as sensitization or tolerance. Addiction and dependence involve psychological and physical reliance on psychoactive substances, with treatments ranging from psychotherapy and medication to emerging psychedelic therapies; global prevalence is highest for alcohol, cannabis, and opioid use disorders.

The legality of psychoactive drugs has long been controversial, shaped by international treaties like the 1961 Single Convention on Narcotic Drugs and national laws such as the United States Controlled Substances Act. Distinctions are made between recreational and medical use. Enforcement varies across countries. While the 20th century saw global criminalization, recent shifts favor harm reduction and regulation over prohibition. Widely used psychoactive drugs include typically legal recreational substances like caffeine, alcohol, and nicotine; prescription-only medications such as SSRIs, opioids, and benzodiazepines; and typically illegal drugs like cannabis, cocaine, and psychedelics.