Sleep disturbances and depressive symptoms are associated closely with daytime dysfunctions, yet few studies have investigated their temporal relationship in a randomized controlled trial. We investigated the inter-relationships among sleep, depressive symptoms and daytime functioning following an integrative body-mind-spirit (I-BMS) intervention. One hundred and eighty-five participants (mean age 55.28 years, 75.1% female) with co-existing sleep and depressive symptoms were randomized to I-BMS or waiting-list. Daytime functioning variables included the daytime dysfunction items of the Pittsburg Sleep Quality Index (PSQI-day), Somatic Symptom Inventory, Hospital Anxiety Depression Scale and Short Form Health Survey collected at baseline, post-treatment and 3-month follow-up. Sleep and depressive symptoms were measured by the sleep items of the PSQI (PSQI-night) and Center for Epidemiological Studies Depression Scale (excluding the sleep item) (CESD-M). Regression and path analyses were used to understand the role of daytime functioning in sleep and depressive symptoms. We found significant group and time effects on almost all daytime variables and significant group × time interactions on PSQI-day and somatic symptoms. The adjusted regression model showed that CESD-M was associated with all daytime variables. However, PSQI-night was associated only with PSQI-day. Path analyses indicated that PSQI-day bridged PSQI-night and CESD-M in a two-way direction after the I-BMS intervention. The conclusion was that, following I-BMS intervention, improvement in daytime functioning was related predominantly to improvement in depressive symptoms. Night-time sleep related only to daytime dysfunction that was specific to sleep disturbances. Therefore, 'sleep-specific daytime impairment' could be regarded as a major link from night-time sleep to depressive symptoms. More studies are required to understand the concept of 'sleep-specific daytime impairment'.
Keywords: Functioning variables; Integrative mind-body group; mild to moderate depression; serial mediations; sleep disturbances.
© 2017 European Sleep Research Society.