Preliminary support for the role of reward relevant effort and chronotype in the depression/insomnia comorbidity.

BACKGROUND: The presence of insomnia in the context of depression is linked to a number of poor outcomes including reduced treatment response, increased likelihood of relapse, and greater functional impairment. Given the frequent co-occurrence of depression and insomnia, research into systems and processes relevant to both disorders, specifically reward processing and circadian rhythm disruption, may help parse this complex comorbidity. METHODS: A pilot study was conducted on a sample of 10 veterans with clinically significant depression and insomnia symptoms. Participants completed objective (actigraphy) and subjective (sleep diary) assessments of sleep, self-reports of chronotype, and behavioral tasks assessing reward relevant effort before and after 6 sessions of Cognitive Behavioral Therapy for Insomnia. RESULTS: Insomnia and depression significantly improved following CBT-I. Subjective sleep parameters significantly improved with large effect sizes. Actigraphy results were nonsignificant, but effect sizes for sleep efficiency and onset latency were in the medium range. Chronotype shifted significantly toward morningness following CBT-I, and an earlier chronotype at baseline was associated with increased reward effort following treatment. Changes in chronotype, depression and insomnia were not associated with changes in effort. LIMITATIONS: Findings are limited by small sample size and lack of randomized control group. CONCLUSIONS: Findings should be interpreted as hypothesis generating in the service of furthering research aimed at uncovering potential mechanisms underlying the depression/insomnia comorbidity. Analyses of sleep data in extant datasets of reward processing impairments in depression as well as original projects aimed at exploring potential sleep, circadian rhythm, and reward interactions in depression are encouraged.

Meta-Analysis of the Antidepressant Effects of Acute Sleep Deprivation.

OBJECTIVE: To provide a quantitative meta-analysis of the antidepressant effects of sleep deprivation to complement qualitative reviews addressing response rates. DATA SOURCES: English-language studies from 1974 to 2016 using the keywords sleep deprivation and depression searched through PubMed and PsycINFO databases. STUDY SELECTION: A total of 66 independent studies met criteria for inclusion: conducted experimental sleep deprivation, reported the percentage of the sample that responded to sleep deprivation, provided a priori definition of antidepressant response, and did not seamlessly combine sleep deprivation with other therapies (eg, chronotherapeutics, repetitive transcranial magnetic stimulation). DATA EXTRACTION: Data extracted included percentage of responders, type of sample (eg, bipolar, unipolar), type of sleep deprivation (eg, total, partial), demographics, medication use, type of outcome measure used, and definition of response (eg, 30% reduction in depression ratings). Data were analyzed with meta-analysis of proportions and a Poisson mixed-effects regression model. RESULTS: The overall response rate to sleep deprivation was 45% among studies that utilized a randomized control group and 50% among studies that did not. The response to sleep deprivation was not affected significantly by the type of sleep deprivation performed, the nature of the clinical sample, medication status, the definition of response used, or age and gender of the sample. CONCLUSIONS: These findings support a significant effect of sleep deprivation and suggest the need for future studies on the phenotypic nature of the antidepressant response to sleep deprivation, on the neurobiological mechanisms of action, and on moderators of the sleep deprivation treatment response in depression.