AbstractBased on self‐rating questionnaire evaluation of symptoms of major affective disorder, 67% of patients who presented to a major sleep disorders center reported an episode of depression within the previous 5 years, and 26% described themselves as depressed at presentation. Furthermore, patients with sleep apnea, narcolepsy, or sleep‐related periodic leg movements all averaged high rates of self‐reported depressive symptomatology, which suggests that sleep disorders should be considered in the differential diagnosis of affective disorders, and vice versa. Change scores on the Profile of Mood States were obtained for four subgroups of patients who were undergoing conventional treatment. Significant improvement in scores was observed in obstructive sleep apneics treated surgically and in patients with sleep‐related periodic leg movements placed on clonazepam, but not in narcoleptics placed on a stimulant or in insomniacs with chronic use of sedative‐hypnotic drugs who were withdrawn from sleep medications. Differential improvement in POMS scores after treatment for different sleep disorders could mean that the relationship to mood disturbance differs for different sleep