Daylight Heals, Night Light Steals: The surprising Link Between Light Exposure and Mental Health

In a recent study published in the journal Nature Mental Health, an international team of researchers conducted a large-scale, cross-sectional analysis of sleep, light exposure, mental health, and physical activity to understand the association between light exposure during the day and night and the risk of self-harm and psychiatric disorders.

Growing evidence indicates that healthy circadian rhythms play a pivotal role in mental health, with disrupted sleep cycles implicated in various psychiatric disorders. The suprachiasmatic nuclei in the hypothalamus in humans house the central circadian rhythm, which modulates physiological functions, behavior, cognition, as well as basic cellular functions. These circadian rhythms are, in turn, modulated by the patterns of light exposure during the day and at night.

Robust and stable circadian rhythms have evolved in biological systems under the predictable patterns of light exposure during the day and darkness during the night. In the modern age, humans spend most of the day indoors under artificial electric lighting, which is relatively dim compared to natural light during the day and bright at night. This disruption of the natural patterns of light exposure can subsequently disturb the circadian rhythms and result in psychiatric disorders and adverse mental health outcomes.