The relationship between insomnia and depressive symptoms: genuine or artifact?

Somatic symptom overlap between depression and insomnia has emerged as a major concern. Self-report measures such as the Beck Depression Inventory Second Edition (BDI-II) include somatic symptoms related to depression that are also present in the research diagnostic criteria for insomnia. This study aimed firstly to examine the relationship between the cognitive and somatic factors of the BDI-II and global scores on the Pittsburgh Sleep Quality Index (PSQI) in individuals presenting for insomnia treatment and secondly to examine whether treating insomnia in depressed individuals with insomnia will lead to a reduction in their depressive symptoms and whether this reduction is related to a decrease in the somatic or cognitive factors of depressive symptoms.

A total of 379 individuals (133 males and 246 females), with a mean (M) age of 49.95 (standard deviation [SD] = 14.15) years, were used to address the first aim. To address the second aim, a total of 64 participants (27 males and 37 females) with both insomnia and depressive symptoms were treated for their insomnia. Their ages ranged between 22 and 87 (M = 50.97, SD = 15.13) years.

A significant relationship was found between both the cognitive and somatic factors of the BDI-II and global scores on the PSQI. Furthermore, although results in this study are only suggestive, they lend support to the idea that the relationship between insomnia and depression is not due to somatic symptom overlap. Results may also support the hypothesis that insomnia is primary to the presentation of depressive symptoms.

Clinicians and health care providers could initially treat insomnia in individuals suffering from insomnia who also experience depressive symptoms, as this will not only remit insomnia but also abate the accompanying depressive symptoms.