This study will examine the use of a transdiagnostic Sleep and Circadian Treatment (TranS-C) in treating Major Depressive Disorder (MDD) in Chinese adults. Sleep disturbance is highly comorbid with a range of psychological disorders, especially MDD. MDD is a major public health concern and a leading cause of disability worldwide. A shift in treatment perspectives, from a disorder-specific approach to a transdiagnostic approach, has been proposed. While the disorder-specific approach tends to understand and treat different mental disorders as independent psychological problems, the transdiagnostic approach aims to identify common clinical features (e.g. sleep disturbances) across a range of psychological disorders. The transdiagnostic approach would potentially facilitate timely dissemination of evidence-based psychological treatments and contribute to significant public health implications.

This study will be a randomized controlled trial on the efficacy of TranS-C for MDD. TranS-C integrates elements of evidence-based interventions, namely cognitive-behavioral therapy for insomnia, delayed sleep phase type, and interpersonal and social rhythm therapy. Prior to all study procedures, an online informed consent (with phone support) will be obtained from potential participants. Around 150 eligible participants will be randomly assigned to the TranS-C group or the care-as-usual control group (CAU group) in a ratio of 1:1. The randomization will be performed by an independent assessor using a computer-generated list of numbers. No deception is necessary. Participants in the TranS-C group will receive TranS-C once per week for 6 consecutive weeks respectively. The group treatment will be delivered by a clinical psychology trainee under the supervision of a clinical psychologist. The TranS-C group will complete a set of online/paper-and-pencil questionnaires before the treatment commences, 1-week, and 12-week after the treatment sessions are completed. The CAU group will complete the same set of online/paper-and-pencil questionnaires during the same periods.

Inclusion Criteria:

1. Hong Kong Citizen who is able to speak Cantonese and read Chinese;
2. Aged ≥ 18 years;
3. Presence of the DSM-IV diagnostic criteria of MDD based on Chinese-bilingual Structured Clinical Interview for DSM-IV (SCID);
4. Score on PHQ-9 is 10 or above;
5. More than 1 sleep or circadian problem according to the Sleep and Circadian Problem Checklist, including time needed to fall asleep more than 30 minutes for more than 3 nights per week, less than 6 hours of sleep per night or at least 9 hour of sleep per night per 24 hour period for at least 3 nights per week, variability in the sleep-wake schedule at least 2.78 hours within a week, and falling asleep after 2 am on at least 3 nights per week;
6. Adequate opportunity and circumstances for sleep to occur; and
7. Willing to give informed consent and comply with the trial protocol.

Exclusion Criteria:

1. Presence of other psychiatric disorders as defined by the DSM-IV diagnostic criteria using SCID;
2. Major medical or neurocognitive disorders that make participation infeasible;
3. Have suicidal ideation based on Beck Depression Inventory (BDI-II) Item 9 score ≥ 2;
4. Untreated sleep disorders based on SLEEP-50 (≥ 7 on narcolepsy; ≥ 15 on OSA; ≥ 7 on RLS/PLMD);
5. Past or current involvement in a psychological treatment programme for depression and/or sleep problems;
6. Shift work, pregnancy, work, family, or other commitments that interfere with regular night-time sleep patterns;
7. Hospitalization; and
8. A change in psychotropic drugs within 2 weeks before baseline assessment