Delayed sleep phase in young people with unipolar or bipolar affective disorders

Background: Circadian disturbances may play a key role in the pathogenesis of some forms of mood disorders. Despite marked changes in circadian rhythms during the normal course of adolescence and young adulthood, less is known about changes in the 24-h sleep-wake cycle in young persons with mood disorders. Methods: Seventy-five young participants with mood disorders (unipolar: n=46, 20.1±4.7 years old; bipolar I or II: n=29, 23.2±4.3) and 20 healthy participants (24.8±2.5 years old) underwent actigraphy monitoring during a depressive phase over seven consecutive days and nights. Sleep phase delay was defined as mean sleep onset ≥1:30 am and/or sleep offset ≥10:00 am. Results: A delayed sleep phase was found in 62% of participants with bipolar disorders when depressed, compared with 30% of those with unipolar depression (χ2=6.0, p=0.014) and 10% of control participants (χ2=11.2, p