Central nervous system depressants which were specifically produced for therapeutic uses due to their calming effects and sleep-induction and anxiety-reduction effects. Includes barbiturates, meprobamate, and benzodiazepines. Used at low doses for daytime application as anxiety reducers, or at higher doses for inducement of sleep. All produce high levels of tolerance over the long term, and ceasing use can engender potentially life-threatening withdrawal symptoms. Severe abuse can produce dangerous intoxication effects, while chronic abuse can produce a wide range of serious, often irreversible, problems.