Treatment of Delayed Sleep Phase Disorder in Adolescents and Young Adults

All participants will receive morning bright light therapy using Re-timer glasses, a common treatment for Delayed Sleep Phase Disorder. Re-timer is a light device, worn just like a pair of glasses that produces a 100% UV-free light, which helps your body recognise when to be awake and when to sleep. Following basic sleep education, participants will be instructed to advance their wake up time by half an hour each day and wear the Re-timer bright light glasses for 30 minutes immediately after rising from bed. 1) Green Bright Light: Participants will follow instructions regarding their sleep timing (as explained above) and undergo morning bright light therapy with green wavelength light. 2) Green Bright Light plus Exercise: Participants will follow instructions regarding their sleep timing, undergo morning bright light therapy with green wavelength light and complete 30 minutes of exercise immediately after rising from bed each morning, (whilst wearing the Re-timer glasses), by playing a motion sensing video game. 3) Red Bright Light: Participants will follow instructions regarding their sleep timing (as explained above) and undergo morning bright light therapy with red wavelength light. 4) Red Bright Light plus Exercise: Participants will follow instructions regarding their sleep timing, undergo morning bright light therapy with red wavelength light and complete 30 minutes of exercise immediately after rising from bed each morning, (whilst wearing the Re-timer glasses), by playing a motion sensing video game. Participants attend three treatment sessions in total, which will be administered by a Psychologist, Clinical Psychologist or Provisional Psychologist. Each of the 3 treatment sessions are one week apart (e.g., 21 days of treatment) and will last approximately 1.5 hours each time. Treatment will involve basic sleep education regarding normal sleep and the circadian rhythm, as well as individualised behavioural instructions, including how and when to use the Re-timer glasses, when to avoid bright light in the evening, and in the exercise conditions, the duration, intensity and type of exercise prescribed. Behavioural instructions will differ for each participant, depending on the severity of sleep timing delay and desired bed and wake up times. Participants will advance their wake up time by half an hour each day until their desired wake up time is achieved (usually no earlier than 6am). Therefore, the number of days spent advancing sleep timing will depend upon participant’s natural wake up time and their desired wake up time. For example, someone waking at noon, who wishes to wake at 7am, may require 10 days of advancement. Whereas, someone waking at 10am, who wishes to wake at 8am may only require 4 days of advancement. Following sleep timing advancement, participants will undergo a period of consolidation, to maintain their desired sleep schedule, for the remainder of the treatment period. Adherence to the interventions will be assessed daily, by self- and parent-report on the sleep diary (e.g., how long did you wear the Re-timer glasses/ exercise for this morning in minutes?). As an additional objective measure of sleep timing and activity levels, actigraphic data will be collected.