Day-to-day associations between subjective sleep and affect in regard to future depression in a female population-based sample.

Background: Poor sleep is a risk factor for depression, but little is known about the underlying mechanisms.

Aims: Disentangling potential mechanisms by which sleep may be related to depression by zooming down to the 'micro-level' of within-person daily life patterns of subjective sleep and affect using the experience sampling method (ESM).

Method: A population-based twin sample consisting of 553 women underwent a 5-day baseline ESM protocol assessing subjective sleep and affect together with four follow-up assessments of depression.

Results: Sleep was associated with affect during the next day, especially positive affect. Daytime negative affect was not associated with subsequent night-time sleep. Baseline sleep predicted depressive symptoms across the follow-up period.

Conclusions: The subtle, repetitive impact of sleep on affect on a daily basis, rather than the subtle repetitive impact of affect on sleep, may be one of the factors on the pathway to depression in women.