depressant, any one of various substances that diminish functional activity, usually by depressing the nervous system. Barbiturates, sedatives, alcohol, and meprobamate are all depressants. Depressants have various modes of action and effects. Some are primarily used medically to relieve emotion stress, anxiety, and tension; others induce sleep, and still others are used to relieve pain. Depressants also reduce the rate and force of contraction of the heart and are used in the treatment of some forms of heart disease. Many depressants can induce psychological dependence and addiction (see drug addiction and drug abuse). Typically, overdosage results in confusion, coma, and convulsions. In many cases, the effects of one depressant are intensified if another depressant is taken at the same time, e.g., if barbiturates are taken with alcohol. Because of their potential for abuse, there are now strict regulations regarding the dispensing of many depressant drugs.