A depressant, or central depressant, is a drug or endogenous compound that lowers or depresses arousal levels and reduces excitability. Depressants are also occasionally referred to as “downers” as they lower the level of arousal when taken. Stimulants or “uppers” increase mental and/or physical function are the functional opposites of depressants. Depressants are widely used throughout the world as prescription medicines and as illicit substances.