The effect of poor sleep quality on depressive symptoms has been consistently found. The aim of our study was to assess the heterogenity of sleep quality in relations between circadian preferences and depressive symptomatology among major depression patients.

The sample was consisted of 225 patients with first diagnosis major depression. Mean age of the sample was 29.92 (SD±10.49). The patients completed a package of psychological instruments including the Morningness–Eveningness Questionnaire, Pittsburgh Sleep Quality Index, and Beck Depression Inventory.

The latent structure of sleep quality among first diagnose major depressive patients was examined by applying latent class analysis (LCA) to the seven components of the PSQI, using Mplus 4.01. We also examined the latent structure of sleep quality in conjunction with the MEQ and BDI scores.

We found that evening-type depressive patients were more prone to report greater scores of subjective sleep quality, sleep latency, sleep duration, use of sleep medication and daytime dysfunction sub-scales of the PSQI. Direct effect of evening-type chronobiological preference was significantly linked to greater depression scores. Indirect effects of chronobiological characteristics through components of the PSQI were only significant for use of sleep medication and daytime dysfunction sub-scales of the PSQI (p<.05).

These findings suggest that sleep quality in general operates and influences on depression in concert with chronobiological characteristics; however, the construct of sleep quality appear like to be heterogeneous in nature and is influential on severity of depression symptoms through distinct mechanisms among depressive patients.