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Colloquially known as "downers", depressants or central nervous system (CNS) depressants are drugs that lower neurotransmission levels, decrease the electrical activity of brain cells, or reduce arousal or stimulation in various areas of the brain. Some specific depressants do influence mood, either positively (e.g., opioids) or negatively, but depressants often have no clear impact on mood (e.g.,... Wikipedia