Applied ergonomicsAug 10, 2014

Bright morning light improves mood and alertness but not thinking skills

Circadian Biology Weekly Brief ↗PubMed ↗DOI ↗

Updated Apr 5, 2026

Abstract

Intense morning illumination was tested in 33 healthy individuals and negatively impacted sustained attention performance.

Exposure to bright light may improve subjective alertness and mood.
Contrarily, bright light could hinder performance on tasks requiring sustained attention.
Bright light exposure had no significant effect on serum melatonin levels.
Adequate lighting should consider both visual and non-visual demands.

Simplified

Cognitive performance and alertness are two determinants for work efficiency, varying throughout the day and depending on bright light. We conducted a prospective crossover study evaluating the impacts of exposure to an intense, early morning illumination on sustained attention, alertness, mood, and serum melatonin levels in 33 healthy individuals. Compared with a dim illumination, the intense illumination negatively impacted performance requiring sustained attention; however, it positively impacted subjective alertness and mood and had no impact on serum melatonin levels. These results suggest that brief exposure to bright light in the morning hours can improve subjective measures of mood and alertness, but can also have detrimental effects on mental performance as a result of visual distraction. Therefore, it is important that adequate lighting should correspond to both non-visual and visual demands.

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Bright morning light improves mood and alertness but not thinking skills

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