Clinical Research Directory

Inclusion Criteria for Healthy Control Group: * Adults aged 18 to 65 years living in Hong Kong * Being fluent and literate in Cantonese * A Patient Health Questionnaire-9 (PHQ-9) score of below 5, indicating minimal or no depressive symptoms * Accessibility to an Internet-enabled mobile device (iOS or Android operating system) * Willingness to provide informed consent and comply with the trial protocol. Exclusion Criteria for Healthy Control Group: * Presence of any psychiatric disorder(s) as assessed by MINI * Shift work, pregnancy, or work, family, or other commitments that interfere with regular sleep-wake patterns * Presence of other untreated sleep disorders based on cut-off scores of individual sections in SLEEP-50. We will not exclude those with current suicidal risks (i.e., non-fleeting intent or plan), which is a common symptom of MDD. However, if serious suicidal risk (i.e., PHQ-9 Item 9 score \> 2) is identified, the participant will be referred to the PI (a clinical psychologist) for further assessment and professional mental health services if deemed necessary. Inclusion Criteria for the Major Depressive Disorder (MDD) group: * Adults aged 18-65 years living in Hong Kong * Being fluent and literate in Cantonese * A PHQ-9 score of at least 10, indicating a moderate level of depression. * Meeting the DSM diagnostic criteria for current MDD according to the Mini International Neuropsychiatric Interview (MINI) * Experiencing ≥ 1 sleep or circadian problem in the past 3 months according to the sleep and circadian problems checklist (i.e., time needed to fall asleep ≥ 30 minutes, wake after sleep onset ≥ 30 minutes, \< 6-hour sleep per night or ≥ 9-hour sleep per night per 24-hour period, and falling asleep after 2:00 AM ≥ 3 nights per week; and variability in the sleep-wake schedule ≥ 2.78 hours within a week) * Access to an Internet-enabled mobile device (iOS or Android operating system) * Willingness to provide informed consent and comply with the trial protocol. Exclusion Criteria for the Major Depressive Disorder (MDD) group: * Severe medical or neurocognitive disorder(s) that make participation unsuitable based on the team's clinical experience * Presence of other psychiatric disorders as assessed by MINI * A history of electroconvulsive therapy (ECT) * Current involvement in any psychological treatment programme that targets depression and/or sleep and circadian problems * A change in the class or dose of any prescribed psychotropic drugs within 6 weeks before the baseline assessment * Shift work, pregnancy, or work, family, or other commitments that interfere with regular sleep-wake patterns * Presence of other untreated sleep disorders, including narcolepsy, obstructive sleep apnoea (OSA), and restless leg syndrome (RLS)/periodic leg movement disorder (PLMD) based on the cut-off scores of SLEEP-50 (narcolepsy ≥ 7; OSA ≥ 15; RLS/PLMD ≥ 7)