Effects of CBT and BLT in Youth With Unipolar Depression and Evening Chronotype

Adolescence is a vulnerable period often linked to the emergence of emotional and behavioural difficulties, particularly major depressive disorder (MDD). It is also associated with a gradual change of circadian rhythm characterised by an intrinsic phase delay with an increased evening preference linked to pubertal development. The optimal treatment for youth depression remains controversial. CBT for depression (CBT-D) is one of the most extensively tested psychological treatments for managing mild to moderate depression. Nonetheless, well-designed randomised controlled trials (RCTs) of CBT-D conducted in young people were limited, and the existing research showed that more than 60% of youth did not respond to psychological treatments. Therefore, improving the current model of care and outcomes in youth with depression is imperative, yet rigorous controlled trials of the treatment for youth depression remain limited. In addition, despite the close interplay between circadian disruption and mood problems, little is known as to whether the adjunctive circadian-focused intervention could potentially enhance the treatment outcome of adolescent depression, especially in those with circadian vulnerability (eveningness).

The study is a randomised controlled trial that examines the effects of cognitive behavioural therapy and bright light therapy in youth with unipolar depression and evening chronotype. Eligible participants will be randomised to one of the following groups: CBT-D plus bright light therapy (CBTD+BLT), CBT for depression only (CBTD-BLT), or waiting list control (WL) using an automated online system. For both treatment groups, the intervention will consist of 8 weekly group sessions (90-min, 4-6 adolescents in each group) of CBT-D delivered in the afternoon/evening after school within a 10-week window. The intervention is structured and based on the well-established CBT elements for treating depression, which combines cognitive and behavioural strategies targeting the common difficulties and problems encountered by depressed adolescents. Participants in both treatment groups will also be introduced to the daily light-based intervention by wearing a portable light device (Re-timers) at home for 30 minutes daily for seven weeks, starting from the second week of the group intervention. Participants in the CBTD-BLT group will receive a placebo light intervention, where they will be exposed to dim red light (50 lux), whereas participants in the CBT-D plus light therapy group will receive the active light treatment. All participants initially randomised to the WL condition will be offered treatment opportunities at the end of the WL period.

The primary aim of the study is to test the efficacy of CBT-D and CBT-D plus bright light therapy in reducing depression severity in adolescents with depression and eveningness when compared with the waiting list control. The secondary aim of the study is to examine the effects of CBT-D and CBT-D plus bright light therapy on the subjective and objective sleep and circadian measures, as well as the measures of quality of life, daytime symptoms and functioning (e.g., sleepiness, fatigue).

• Change of Self-report Depressive Symptoms [Time frame: Baseline and one-week post-treatment/Week 9 for all participants, and post-treatment 1-month follow-up and post-treatment 6-month follow-up for the participants in the treatment groups]
• Change of Suicidal Ideation [Time frame: Baseline and one-week post-treatment/Week 9 for all participants, and post-treatment 1-month follow-up and post-treatment 6-month follow-up for the participants in the treatment groups]
• Change in Self-Report Chronotype Measures [Time frame: Baseline and one-week post-treatment/Week 9 for all participants, and post-treatment 1-month follow-up and post-treatment 6-month follow-up for the participants in the treatment groups]
• Change in Self-Report Circadian Typology [Time frame: Baseline and one-week post-treatment/Week 9 for all participants, and post-treatment 1-month follow-up and post-treatment 6-month follow-up for the participants in the treatment groups]
• Change in Insomnia Symptoms [Time frame: Baseline and one-week post-treatment/Week 9 for all participants, and post-treatment 1-month follow-up and post-treatment 6-month follow-up for the participants in the treatment groups]
• Change in Sleep Quality [Time frame: Baseline and one-week post-treatment/Week 9 for all participants, and post-treatment 1-month follow-up and post-treatment 6-month follow-up for the participants in the treatment groups]
• Change in Total Sleep Time (TST) measured by sleep diary [Time frame: Baseline and one-week post-treatment/Week 9 for all participants, and post-treatment 1-month follow-up and post-treatment 6-month follow-up for the participants in the treatment groups]
• Change in Sleep Onset Latency (SOL) measured by sleep diary [Time frame: Baseline and one-week post-treatment/Week 9 for all participants, and post-treatment 1-month follow-up and post-treatment 6-month follow-up for the participants in the treatment groups]
• Change in Wake After Sleep Onset (WASO) measured by sleep diary [Time frame: Baseline and one-week post-treatment/Week 9 for all participants, and post-treatment 1-month follow-up and post-treatment 6-month follow-up for the participants in the treatment groups]
• Change in Sleep Efficiency (SE) measured by sleep diary [Time frame: Baseline and one-week post-treatment/Week 9 for all participants, and post-treatment 1-month follow-up and post-treatment 6-month follow-up for the participants in the treatment groups]
• Change in Total Sleep Time (TST) measured by actigraphy [Time frame: Baseline and one-week post-treatment/Week 9 for all participants, and post-treatment 1-month follow-up and post-treatment 6-month follow-up for the participants in the treatment groups]
• Change in Sleep Onset Latency (SOL) measured by actigraphy [Time frame: Baseline and one-week post-treatment/Week 9 for all participants, and post-treatment 1-month follow-up and post-treatment 6-month follow-up for the participants in the treatment groups]