Drug use

Although the DSM precludes a diagnosis of major depressive disorder for those presenting with "the direct physiological effects of a substance", sedative hypnotic drugs such as alcohol and benzodiazepines increase the risk of a syndrome that is, at least, highly similar to major depression. This increased risk may be due in part to the effects of drugs on neurochemistry, such as decreased levels of serotonin and norepinephrine. Alcoholism or excessive alcohol consumption significantly increases the risk of developing this syndrome. Benzodiazepines, a class of medication which are commonly used to treat insomnia, anxiety and muscular spasms, also increase the risk. Chronic, severe depression can develop as a result of chronic use of benzodiazepines or as part of a protracted withdrawal syndrome.