Psychoactive substances are natural or synthetic substances that act on the central nervous system and alter mental processes such as mood, perception, cognition, consciousness, and behaviour. These substances may be legally prescribed medications (e.g., pain medications or sedatives), legally available substances such as alcohol or caffeine, or controlled or illicit drugs. Psychoactive substances can be used for medical, social, cultural, or recreational purposes, but some carry risks of misuse, dependence, and health or social harms when used in harmful ways.
