A systematic review on sleep alterations anticipating the onset of bipolar disorder

Background: Sleep alterations are frequent occurrence in Bipolar Disorder (BD), both in acute and interepisodic phases. Sleep alterations have been also described both long before BD onset, as aspecific risk syndromes, or as immediate prodromes of BD onset. The aim of the present study is to systematically review the relationship between sleep alterations anticipating for the full-blown onset of BD, both in general and according to specific polarities of onset. Methods: A systematic literature research according to PRISMA statement and considering: 1. prospective studies about BD patients’ offspring with sleep alterations who later developed BD. 2. prospective studies assessing patients with sleep disorders who later developed BD. 3. retrospective studies on BD patients where sleep alterations before BD onset of the disease were reported. Results: A total of 16 studies were included in this review. Sleep disturbances may frequently appear 1 year before the onset of BD or more, often during childhood or adolescence. A decreased need for sleep may precede the onset of the illness, specially a manic episode, while insomnia appears to anticipate either a manic or a depressive episode. Hypersomnia seems to precede bipolar depressive episodes. Conclusions: Sleep alterations frequently appear long before the onset of BD, and appear to be related specifically to the polarity of the index episode. The detection and treatment of sleep alterations in special high risk populations may help achieving an earlier detection of the illness.