0717 THE ROLE OF LIGHT AND PHASE OF ENTRAINMENT IN SEASONAL AFFECTIVE DISORDER

• Published in: Sleep (New York, N.Y.) N.Y.), 2017-04, Vol.40 (suppl_1), p.A265-A265
• Main Authors: DuPont, CM, Miller, MA, Hasler, BP, Roecklein, KA
• Format: Article
• Language: English
• Subjects: Jet lag; Light; Seasonal affective disorder
• ISSN: 0161-8105; 1550-9109
• DOI: 10.1093/sleepj/zsx050.716

Abstract Introduction: The phase shift hypothesis suggests that seasonal affective disorder (SAD) is caused by a circadian phase delay in winter. As light is the most robust entrainment cue, light exposure is proposed to be involved in SAD etiology. Blue light may be of particular interest as it is most effective for circadian photoreception. The timing of light exposure is also important for entrainment, as morning light leads to a phase advance, and evening light to a phase delay. Therefore, we hypothesized that evening circadian phase in winter will mediate the relationship between morning and/or evening light exposure and depression symptomatology. Methods: Individuals (n=28; 75% female; aged 18–65) with varying degrees of seasonality were recruited in Pittsburgh during the winter. Participants wore an actigraphy watch with a photodiode for one week. Light was analyzed for blue wavelength ranges (400-500nm; photons/cm2/sec) across a minimum of four days. Total daily light exposure was averaged across each day. The Composite Scale of Morningness was used as a proxy for circadian phase. The Structured Clinical Interview Guide for the Depression Rating Scale, SAD Version (SIGH-SAD) was used to measure depression symptomatology. Age and gender will be used as covariates. Results: Circadian preference was significantly associated with higher SIGH-SAD scores (R2=0.176, β= -0.40, p=0.04), while controlling for age and gender. There was no significant association between light exposure and circadian phase (R2=0.020, β=0.05, p=0.20), or light exposure and SIGH-SAD scores (R2=0.059, β=0.23, p=0.32), thus precluding mediation. Conclusion: The current study replicated previous findings that a delayed circadian phase is associated with greater depressive symptomatology. However, there is currently no evidence to suggest the role of total daily blue light exposure on depressive symptomatology or circadian phase, as estimated by circadian timing preference. Support (If Any): Supported by R01MH103313 (K.R.)