Abstract
BACKGROUND: Disturbed sleep is a common problem in both chronic pain and major depressive disorder (MDD). Moreover, many patients with chronic pain are depressed. OBJECTIVES: To examine the effects of depression on the sleep behaviour of chronic pain patients by comparing patients who did or did not meet diagnostic criteria for MDD. METHODS: A total of 60 patients with chronic musculoskeletal pain underwent structured diagnostic interviews for MDD and insomnia, and completed questionnaires assessing pain severity, disability, sleep quality, beliefs and attitudes about sleep, and sleep hygiene. For four consecutive days, they also completed a sleep diary, and reported on sleep hygiene practices and presleep arousal. RESULTS: Thirty-three patients (55%) met diagnostic criteria for MDD, most of whom (n=32 [97%]) also fulfilled criteria for insomnia disorder. Insomnia was also common among patients without MDD (21 of 27 [78%]). Participants with MDD had higher self-reports of pain, disability, dysfunctional beliefs about sleep, and, on a prospective basis, greater presleep arousal and poorer sleep hygiene. However, diary assessments of specific sleep parameters (eg, sleep onset latency, total sleep time, sleep efficiency) did not differ between the groups. DISCUSSION: Chronic pain patients with comorbid MDD exhibited more dysfunctional beliefs about sleep, poorer sleep hygiene practices and greater presleep arousal; however, diary-recorded sleep characteristics may not differ from those of patients without MDD. Chronic pain itself may disturb sleep so extensively that MDD introduces little additive effect. CONCLUSION: MDD in chronic pain may be related to the cognitive and behavioural aspects of insomnia, rather than to an incremental disturbance in the initiation or maintenance of sleep.