Translational psychiatryFeb 1, 2017

How the timing of light exposure relates to mood and brain activity

Circadian Biology Weekly Brief ↗PubMed ↗DOI ↗OA ↗

Updated Apr 2, 2026

Abstract

Circadian disruption by nighttime light is associated with increasing incidence of mood disorders.

Pervasive exposure to artificial light at night complicates synchronization of biological processes regulated by .
Many physiological systems, including sleep-wake behavior and hormone secretion, are influenced by these rhythms.
Circadian disruption may impair brain regions responsible for emotion and mood regulation.
Altered neuroplasticity, neurotransmission, and clock gene expression could be mechanisms through which aberrant light exposure impacts mood.
Emerging evidence highlights the health effects of nighttime light exposure on mental well-being.

Simplified

Temporal organization of physiology is critical for human health. In the past, humans experienced predictable periods of daily light and dark driven by the solar day, which allowed for entrainment of intrinsic to the environmental light-dark cycles. Since the adoption of electric light, however, pervasive exposure to nighttime lighting has blurred the boundaries of day and night, making it more difficult to synchronize biological processes. Many systems are under circadian control, including sleep-wake behavior, hormone secretion, cellular function and gene expression. Circadian disruption by nighttime light perturbs those processes and is associated with increasing incidence of certain cancers, metabolic dysfunction and mood disorders. This review focuses on the role of artificial light at night in mood regulation, including mechanisms through which aberrant light exposure affects the brain. Converging evidence suggests that circadian disruption alters the function of brain regions involved in emotion and mood regulation. This occurs through direct neural input from the clock or indirect effects, including altered neuroplasticity, neurotransmission and clock gene expression. Recently, the aberrant light exposure has been recognized for its health effects. This review summarizes the evidence linking aberrant light exposure to mood.

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How the timing of light exposure relates to mood and brain activity

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