A case-control study of frequent nightmares in patients with major depressive disorder (MDD)

Abstract

Introduction: Nightmare disturbance is a common yet often neglected sleep complaint in patients with major depressive disorder (MDD). The aims of the present study were to establish the clinical, psychosocial, and polysomnographic profiles of the depressed patients with frequent nightmares through a case-control study. Methods: Three groups of participants were recruited from the psychiatric outpatient clinic of a regional hospital and the local community in Hong Kong: 1) depressed patients with an active complaint of frequent nightmares, which were defined as having nightmares at least once per week as confirmed by both the retrospective questionnaire assessment and prospective daily mood and dream diary (n=35), 2) age- and gender-matched depressed patients without frequent nightmares (n=35), 3) age- and gender-matched healthy normal controls (n=35). All recruited depressed patients had no comorbid posttraumatic stress disorder (PTSD). Comprehensive in-depth assessments were conducted, including a clinical interview by Mini International Neuropsychiatric Interview (MINI), a battery of questionnaires (Beck Depression Inventory, BDI; Hospital Anxiety and Depression Scale, HADS; Insomnia Severity Index, ISI; Revised-Impact of Event Scale, R-IES; and Beck’s Scale for Suicidal Ideation, BSSI), and one overnight polysomnographic and 7-day of actigraphic sleep assessments. Results: Depressed patients with frequent nightmares were more likely to show melancholic features (p<.05), more severe insomnia symptoms (p<.001), increased anxiety (p<.001) and depressive symptoms (p<.001) as well as a heightened level of suicidal risk (p<.001). They also scored significantly higher on R-IES intrusion (p<.001), avoidance (p<.001), and hyperarousal (p<.001). In addition, depressed patients with frequent nightmares exhibited higher REM density (p<.05), longer REM latency (p<.05) and less REM sleep periods (p<.05) as compared to healthy controls. Whilst there were no significant differences in average sleep parameters as measured by actigraphy, depressed patients with frequent nightmares showed a greater night-to-night variability in wake-after-sleep onset (p<.01), % of wake time (p<.01), % of mobile time (p<.01) and fragmentation index (p<.05). Conclusion: Frequent nightmares represent a distressing sleep problem associated with a more severe clinical presentation and increased suicidality in patients with MDD. Enhanced clinical attention and targeted sleep treatment should be directed to address nightmare complaint in depressed patients.