0466 Effects of Cognitive Behavioural Therapy and Bright Light Therapy on Cognitive Functioning in Youths with Comorbid Insomnia and Eveningness

Abstract Introduction Insomnia and eveningness are common in youth and their co-occurrence may risk daytime cognitive impairments. While cognitive behavioral therapy for insomnia (CBT-I) could effectively improve sleep, its impact on youth cognitive functioning is understudied, and whether addressing circadian disturbances associated with insomnia yields greater cognitive performance benefits remains unclear. This study examined the effects of CBT-I with and without BLT on self-reported and objectively measured cognitive performance in youths with comorbid insomnia and eveningness. Methods A total of 146 participants (mean age = 19.9, SD = 3.2, 55.5% female) with DSM-5 insomnia disorder and eveningness (Reduced Morningness–Eveningness Questionnaire ≤ 11) were randomized into CBT-I with BLT (CBT-I+BLT, N = 50), CBT-I with placebo light (CBT-I-BLT, N = 53), or waitlist group (N = 43). Assessments included subjective sleep quality (Pittsburgh Sleep Quality Index, PSQI), sleep duration (sleep diary and actigraphy), subjective (Cognitive Failures Questionnaire, CFQ) and objective cognitive performance (working memory, episodic memory, executive function). Treatment effects were analyzed using linear mixed models controlled for age, gender, depression, and time of testing. Results A significant Time×Group interaction was observed for sleep quality (PSQI, F = 4.69, p = 0.011), with both CBT-I groups showing a greater improvement than the waitlist (all ps < 0.001). No between-group differences were found for subjective or objective sleep duration (all ps > 0.05). For neurocognitive outcomes, a significant Time×Group interaction was observed for subjective cognitive performance (CFQ total: F = 3.47, p = 0.034; Distractibility: F = 4.88, p = 0.010), with significant within-group improvements observed only in CBT-I-BLT group (CFQ total: p < 0.001; Distractibility: p = 0.009). No significant between-group differences were found for any objective cognitive measures. Conclusion CBT-I significantly improved sleep quality and self-reported cognitive functioning in youth with insomnia and eveningness, though no effects were observed on objectively measured cognitive abilities. Adjunct bright light therapy did not further enhance the treatment effects on cognitive functioning. Longer-term follow-up is warranted to examine the treatment effects over time in this youth population. Support (if any) General Research Fund from the Hong Kong Research Grants Council awarded to SXL (Ref. 17608918).