Psychiatry Research EG

Complaints of sleep difficulties are among the most common symptoms presented by depressed patients. Changes in sleep patterns are components of the diagnostic criteria for depressive illness as well as all major symptom- based rating scales of depression.1,2 Several studies have consistently demonstrated that sleep disturbance is one of the most important predictors of a new or remitting depressive episode.3-5 Also the relief of sleep disturbance is an important determinant of adherence to the treatment plan.1 It is also known that stable sleep-wake rhythms and adequate sleep hygiene are essential in the prevention of relapse in remitted depressed patients. 6 Hence, there may be a complex and potentially mutually reinforcing relationship between sleep disturbance and depression. Epidemiological studies showed that about 20% of subjects complaining of insomnia screened in the general population have been classified as depressed.7,8 A omplaint of persistent insomnia represents an antecedent or significant risk factor for the development of major depression.9,10 With regard to comorbidity, epidemiological studies estimate that complaints of poor sleep quality are observed in between 50% to 90% of subjects with diagnosed depression.11,12 These data indicate a strong bidirectional relationship between sleep and depression, suggesting a common pathophysiology. However, this correlation does not give us any insight into the cause-effect relationship between them. Several studies and hypothetical models have been advanced to explain this shared neurobiology.