Approved Research

Quantifying the Impact of Daylight on Seasonal Patterns in Mood Disorders

Lay summary

Mental disorders are the leading cause of disability worldwide, resulting in enormous personal suffering and socioeconomic costs. There is a consensus in psychiatry that symptoms of bipolar disorder (BD) and major depressive disorder (MDD) display a seasonal pattern of onset in some individuals. Importantly, the current editions of the DSM-5 and ICD-11 adopted a seasonal pattern specifier for BD and MDD. However, very little is known about factors driving seasonality in BD and MDD and how symptom onset is tuned to seasonal changes in daylight duration and intensity.

Studies of the association between hospital admissions of patients and daylight duration (photoperiod), daylight intensity (solar radiation), and maximum temperature have shown that (hypo)manic episodes tend to peak during spring and summer months. In contrast, depressive episodes displayed peaks in early winter and less frequently in summer. Recently, an international team of investigators from over 60 countries determined that greater maximum monthly increase in the amount of solar insolation (the amount of electromagnetic energy from the sun hitting a given location on the Earth) at the BD patient's geographical location was associated with younger age of onset and greater incidence of suicide attempts. My laboratory analyzed National Aeronautics and Space Administration (NASA) global-scale meteorological data from 51 locations in the northern and southern hemispheres and found that the computed monthly measures of solar insolation and the rates of change in solar insolation over a one-year period varied widely, even for cities at the same latitude, due to microclimatic variations between locations including amounts of cloud cover, levels of water vapor, amounts of atmospheric pollutants, and altitude above sea level. This finding highlights the imperative to elucidate daylight effects on objectively measured markers of psychiatric illness.

Here, we propose to develop and apply a novel set of digital tools that will enable systematic characterization of daylight-dependent changes in wrist-worn accelerometer-derived psychomotor activity and brain microstructure imaged via magnetic resonance imaging (MRI). We also propose to develop an interactive website and a mobile health (mHealth) app that will allow the end user (patient) to monitor local trends in sunlight parameters and climatic variables in real time. We will then disseminate these digital tools to the research and clinical communities.  Further, successful completion of our aims will produce foundational information regarding how individual's psychomotor symptom onset and microstructure variation are synchronized to daylight and how this can be disrupted by psychiatric illness.