Effect of Morning Light Exposure on Mood

The objective is to determine the effectiveness of daily morning light therapy for regulating the circadian rhythm to improve mood and reduce suicidal thinking. Our working hypotheses are that daily exposure to the active light for two weeks will 1) lead to a phase advance entrainment of sleep timing relative to a placebo light therapy, 2) lead to improved/sustained mental health outcomes, including suicidal ideation, relative to a placebo light therapy, and that 3) most military Service members will rate the use of a light "headset" device acceptable as a treatment option after their experience.

Over a 3-year period of performance, investigators aim to 1) determine the effectiveness of daily morning active light condition therapy for regulating circadian timing and sleep, 2) determine the effectiveness of daily morning active light condition therapy for sustaining or improving mental health outcomes, including suicidal ideation, relative to placebo light therapy, and 3) determine the acceptability and "buy-in" from military personnel using a daily light headset device.

During this study, 400 military personnel will complete a double-blind, placebo-controlled, counterbalanced, crossover design study of the effects of 30-minutes of daily morning active light condition therapy versus a placebo light therapy on measured sleep and mental health outcomes. Participants will complete two weeks of morning active light condition therapy with a commercially available headset with four built-in light-emitting diode (LEDs) and internal compliance monitors, and two weeks wearing the same type of glasses fit with placebo light-emitting diode (LEDs), in a counterbalanced order, separated by a two-week washout period. An online assessment battery for mental health and suicidal ideation will be completed before and after each treatment period, and sleep/circadian rhythms will be monitored throughout via continuous actigraphy and daily brief sleep/mood/suicidal ideation logs. It is important to note that investigators also monitored sleep/circadian rhythms via 5-channel at-home EEG recordings for the first few participants who completed the study before investigators removed the use of the EEG recording device from the study protocol due to prohibitive costs associated with using the manufacturer's software.

Inclusion criteria

• Ages 18-60 years
• At least an 8th grade reading level
• Score ≥ 5 (i.e., mild depression or greater) on the Patient Health Questionnaire 9 (PHQ-9)
• Service member of any Armed Forces branch, including active duty, Reserve, or National Guard

Exclusion criteria

• Not actively serving in an Armed Force branch
• Scored (i.e., < 5) range on the PHQ-9 (non-depressed)
• Pregnant or trying to become pregnant
• Breastfeeding
• History of psychotic disorder or manic episodes
• Bipolar disorder
• Diseases of the eye
• Have had cataract surgery
• Frequent and light-sensitive migraine headaches
• Self-reported plan to regularly engage in nightshift work during the 6-week course of the study