Most depressed patients suffer from sleep abnormalities, which are one of the critical
symptoms of depression. They are robust risk factors for the initiation and development of depression.
Studies about sleep electroencephalograms have shown characteristic changes in depression such as
reductions in non-rapid eye movement sleep production, disruptions of sleep continuity and
disinhibition of rapid eye movement (REM) sleep. REM sleep alterations include a decrease in REM
sleep latency, an increase in REM sleep duration and REM sleep density with respect to depressive episodes. Emotional
brain processing dependent on the normal sleep-wake regulation seems to be failed in depression, which also promotes the
development of clinical depression. Also, REM sleep alterations have been considered as biomarkers of depression. The
disturbances of norepinephrine and serotonin systems may contribute to REM sleep abnormalities in depression. Lastly,
this review also discusses the effects of different antidepressants on REM sleep disturbances in depression.