Nocturnal Wakefulness Is Associated With Suicidality in Depressed Inpatients: A Polysomnographic Study

Depression is a common psychiatric disorder and a major public health concern. Suicidal ideation and behaviour are frequently reported during major depressive episodes. Sleep disturbances are being progressively recognised as a risk factor for suicide. However, due to the paucity of studies adopting an objective sleep assessment, sleep issues of suicidal depressed individuals have been insufficiently characterised yet. This study aims to compare polysomnographic features of depressed suicidal and non-suicidal subjects. Forty four subjects hospitalised for a major depressive episode, either unipolar or bipolar, underwent polysomnography upon admission to a psychiatric ward. Hamilton depression rating scale was adopted to evaluate depression severity; item 3 of the scale was used to evaluate the presence or absence of suicidal ideation. Polysomnographic features of subjects with and without suicidal thoughts were statistically compared. Suicidal ideation was present in 47.7% of subjects (N = 21). Wake after sleep onset was significantly different in the two subsamples (p = 0.047) and higher in subjects with suicidal ideation (90.6 vs. 67.1 min). In addition, there was a trend toward significance in the comparison of WAKE% (p = 0.053), which was higher in subjects with suicidal ideation (18.6% vs. 14.9%). Mean length of awakenings was higher in the suicidal ideation group (15.37 vs. 7.44 min; p = 0.009). PSG evaluated nocturnal wakefulness was higher in subjects with suicidal ideation, confirming that sleep disturbances play a key role in suicidality. In particular, the length of awakenings may be a powerful marker of suicidality.