Any agent that suppresses, inhibits, or decreases some aspects of central nervous system (CNS) activity.

The main classes of CNS depressants are the sedatives/hypnotics, opioids, and neuroleptics. Examples of depressant drugs are alcohol, barbiturates, anesthetics, benzodiazepines, opiates and their synthetic analogues. Anticonsulvants are sometimes included in the depressant group because of their inhibitory action on abnormal neural activity.

Disorders related to depressants use are classified as psychoactive substance use disorders in ICD-IO in categories F10 (for alcohol), F11 (for opioids), and F13 (for sedatives or hypnotics).

World Health Organization. Lexicon of alcohol and drug terms published by the World Health Organization. Internet. Accessed August 20, 2009.