Abstract
BACKGROUND: Disturbed sleep is a core symptom of major depressive disorder (MDD), with nearly 90% of those with MDD reporting disturbed sleep. However, combining insomnia and hypersomnia into a single diagnostic domain ignores distinct biological differences between those symptom presentations. To better understand depression it may be necessary to explore these symptoms independently, beginning with the more prevalent insomnia. METHOD: The present study evaluated global insomnia symptom severity in a broad sample of MDD outpatients from the Sequenced Treatment Alternatives to Relieve Depression (STAR*D) trial, excluding patients who reported hypersomnia symptoms. The three insomnia-related symptoms from the 16-item Quick Inventory of Depressive Symptomatology- clinician rated (QIDS-C) were combined to create a global insomnia score to classify baseline insomnia severity. A modified depression severity score was then used to assess depression severity (mQIDS-C), excluding sleep-related items. RESULTS: A repeated measures ANCOVA revealed a significant improvement in insomnia score over the acute phase treatment (F = 33.1, d.f. = 6, 9897, p < 0.0001). Improvement in insomnia score over the acute phase treatment remained statistically significant even after controlling for change in depression severity (p = 0.0004). Participants with one point higher insomnia score at baseline were significantly less likely to remit at study exit (odds ratio = 0.88, 95% confidence interval = 0.85, 0.92, p < 0.0001) even after controlling for baseline depression severity. LIMITATIONS: Objective confirmation of sleep profiles was not available. CONCLUSION: Greater severity of insomnia reduces likelihood of MDD remission, and insomnia symptoms improved independent of depression remission.