Self-reported symptoms of insomnia are often inconsistent with objective measures of sleep, including measures derived from actigraphy. Cognitive behavioural therapy for insomnia (CBT-I) effectively improves insomnia symptoms, but whether it reduces subjective-objective sleep discrepancy is not well understood. This study examined whether CBT-I reduces subjective-objective sleep discrepancy against a control condition, and explored associations between changes in discrepancy and changes in sleep-related attitudes. Participants were 112 (age M±SD=47.1 ± 12.3, 67.9% female) adults with comorbid insomnia and major depressive disorder from the TRIAD (Treatment of Insomnia and Depression) study. They were randomized to 7-session CBT-I or control interventions to augment antidepressant pharmacotherapy over 16 weeks. 2-week actigraphy and sleep diary were collected at baseline, in the middle, and at the end of the trial. Subjective-objective sleep discrepancy was operationalised as the discrepancy between self-report and actigraphy time-in-bed (TIB), total sleep time (TST), sleep onset latency (SOL), and wake after sleep onset (WASO). The Dysfunctional Beliefs and Attitudes about Sleep Scale (DBAS) was administered at baseline and mid-intervention. At baseline, self-report TIB and TST were significantly shorter, whilst SOL and WASO longer than those from actigraphy. Multilevel models using daily data showed that after controlling for age and sex, the CBT-I group showed significantly greater reduction in subjective-objective sleep discrepancy in all (except TIB) domains compared to the control group (all p-values<.01). Improvements were evident from mid-intervention. The differential effects of the two interventions on the overall reduction of subjective-objective sleep discrepancy in TST, SOL, and SE (but not WASO) was significantly associated with changes in DBAS from baseline to mid-intervention (all p-values<.05). CBT-I was effective in reducing the subjective-objective sleep discrepancy in patients with comorbid insomnia and major depression. Improvements in subjective-objective sleep discrepancy was associated with improved sleep-related attitudes, a therapeutic target of CBT-I. MH078924, MH078961, MH079256.
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