Digital Insomnia and Circadian Therapy for Reducing Depression Symptoms in College Students

Inclusion Criteria: * Youths aged between 18-24 years old. * Insomnia disorders as determined by DSM-5 criteria with a predominant complaint of difficulty initiating sleep. * Presence of an evening chronotype according to the score on the Horne-Östberg Morning-Eveningness Questionnaire (MEQ) and having a late bedtime of 12:00 am/midnight or later for at least 3 nights per week in the last 3 months. * Presented with at least subclinical depressive symptoms as determined by Patient Health Questionnaire-9 ≥ 10. * Accessibility to a smartphone. Exclusion Criteria: * Having a diagnosed sleep disorder that may potentially contribute to the disruption of sleep quantity and quality other than insomnia and delayed sleep phase syndrome, as ascertained by Structured Diagnostic Interview for Sleep patterns and Disorders (DISP), such as restless leg syndrome and OSA, and narcolepsy. * Diagnosed with neuropsychiatric disorders such as major depressive disorder, anxiety disorders, bipolar affective disorders, schizophrenia, moderate or above suicidality. * Concurrent, regular use of medications known to affect sleep continuity and quality, including both Western medications (e.g. hypnotics, steroids, antidepressants, antihistamines) and over-the-counter medications (e.g. melatonin). * Participate in other psychotherapy (e.g., CBT, mindfulness) currently or in the past three months.