Eveningness Predicts Negative Affect Following Sleep Restriction.

Although considerable research has shown that sleep loss results in decreased positive affect, findings regarding change in negative affect are inconsistent. Such inconsistency may be due in part to variability in individual difference factors, such as chronotype, which is associated with both sleep and affective outcomes. Chronotype represents the tendency to be a morning- or evening-type person and is underpinned by the timing of circadian processes linked to sleep and mental health. The present study examined the predictive effect of chronotype above and beyond that of depression on affective response to sleep restriction in a sample of healthy sleeping adults (n = 73). Participants completed measures of chronotype and depression at baseline and measures of positive and negative affect before and after one night of sleep restriction (4 hours between 4 a.m. and 8 a.m.). Results indicate a large, significant decrease in positive affect following sleep restriction, but no statistically significant change in negative affect. Subsequent analyses showed that chronotype predicted affective response to sleep restriction, such that eveningness predicted a medium, significant increase in negative affect following sleep restriction, controlling for depression-however, there was no association between chronotype and change in positive affect in response to sleep restriction. These findings highlight a differential effect of sleep loss on positive and negative affect and suggest that evening chronotype may confer a distinct vulnerability for increased negative affect following sleep loss.