As with alcohol, the effects of benzodiazepine on neurochemistry, such as decreased levels of serotonin and norepinephrine, are believed to be responsible for the increased depression. Additionally, benzodiazepines can indirectly worsen mood by worsening sleep (i.e., benzodiazepine-induced sleep disorder). Like alcohol, benzodiazepines can put people to sleep but, while asleep, they disrupt sleep architecture: decreasing sleep time, delaying time to REM sleep, and decreasing deep sleep (the most restorative part of sleep for both energy and mood). Just as some antidepressants can cause or worsen anxiety in some patients due to being activating, benzodiazepines can cause or worsen depression due to being a central nervous system depressant—worsening thinking, concentration and problem solving (i.e., benzodiazepine-induced neurocognitive disorder). However, unlike antidepressants, in which the activating effects usually improve with continued treatment, benzodiazepine-induced depression is unlikely to improve until after stopping the medication.In a long-term follow-up study of patients dependent on benzodiazepines, it was found that 10 people (20%) had taken drug overdoses while on chronic benzodiazepine medication despite only two people ever having had any pre-existing depressive disorder. A year after a gradual withdrawal program, no patients had taken any further overdoses.Just as with intoxication and chronic use, benzodiazepine withdrawal can also cause depression. While benzodiazepine-induced depressive disorder may be exacerbated immediately after discontinuation of benzodiazepines, evidence suggests that mood significantly improves after the acute withdrawal period to levels better than during use. Depression resulting from withdrawal from benzodiazepines usually subsides after a few months but in some cases may persist for 6–12 months.
In the DSM-5, Unspecified Depressive Disorder encompasses symptoms that are characteristic of depressive disorders and cause significant impairment in functioning, but do not meet the criteria for the diagnosis of any specified depressive disorders. In the DSM-IV, this was called Depressive Disorder Not Otherwise Specified.Depressive personality disorder (DPD) is a controversial psychiatric diagnosis that denotes a personality disorder with depressive features. Originally included in the DSM-II, depressive personality disorder was removed from the DSM-III and DSM-III-R. Recently, it has been reconsidered for reinstatement as a diagnosis. Depressive personality disorder is currently described in Appendix B in the DSM-IV-TR as worthy of further study.Recurrent brief depression (RBD), distinguished from major depressive disorder primarily by differences in duration. People with RBD have depressive episodes about once per month, with individual episodes lasting less than two weeks and typically less than 2–3 days. Diagnosis of RBD requires that the episodes occur over the span of at least one year and, in female patients, independently of the menstrual cycle. People with clinical depression can develop RBD, and vice versa, and both illnesses have similar risks.Minor depressive disorder, or simply minor depression, which refers to a depression that does not meet full criteria for major depression but in which at least two symptoms are present for two weeks.