Rumination as Mediator between Stress and Sleep Quality: A Diary Study in a Non-Clinical Sample of Women.

A substantial body of literature has established that sleep quality (SQ) is significantly threated by stress. Some evidence suggests that rumination may partially account for this association. However, very little reasearch has examined this hypothesis longitudinally. The present study aims to investigate whether rumination functions as mediator in the stress-SQ relationship within the time interval of a week. 166 women (age range: 18-65) without any psychopathological diagnosis completed an initial questionnaire including trait-assessment measures (Ruminative Response Scale, Perceived Stress Scale, Pittsburgh Sleep Quality Index). After one week, a 6-days diary study was conducted to assess the associations between stress, pre-sleep rumination, and SQ on a daily basis. The results showed an indirect effect of stress on SQ through pre-sleep rumination in all daily assessments. In the midweek assessment, the direct effect was also significant. Concerning the trait-level assessment, stress was associated with higher rumination and lower SQ, but rumination was not a significant mediator of the stress-SQ relationship. Overall, these findings suggest that daily, but not trait rumination significantly mediates stress effects on SQ. Higher perceived stress during the day is related to higher tendency to ruminate before sleeping, leading to lower SQ. Future studies should consider daily-level fluctuations in stress and rumination as possible explanations for SQ outcomes.