Excessive daytime sleepiness (EDS) is often related to depression, and there are several possible relationships between them. EDS can usually occur due to either insomnia or hypersomnia. The symptomatology of depression prominently includes insomnia and the resultant EDS, which may, in such cases, be residual symptoms as a response to antidepressant treatment. Furthermore, insomnia and daytime sleepiness may be short- or long-term side effects of antidepressant treatment as well. The clinical assessment of depression should adequately address whether EDS is a symptom of current depression, a prior depression residual symptom, or a side effect of antidepressant medication. With the purpose of showing current evidence about the investigations of EDS related to depression, we conducted a review of the literature using the following databases: ISI, MEDLINE and SciELO from 1990 to 2007. Although the underlying mechanisms of EDS in depression are complex and intertwined, the comprehensive assessment of this sleep disorder plays a key role in areas related to the prediction of responses to treatment, relapses, and etiological models in depression.
Sleep; disorders of excessive somnolence; sleep initiation and maintenance disorders; depressive disorder