Association of Daytime Light Exposure with Mood, Sleep and Circadian-related Outcomes

Pavankumar Kamat


September 20, 2021


  • A cross-sectional and longitudinal association was seen between daytime light exposure and mood, sleep, and circadian-related outcomes.

Why this matters

  • Findings warrant further research to better understand the role of light in the pathophysiology of mood and sleep disorders by directly measuring circadian physiology and daytime light exposure in a well-controlled longitudinal design.

Study design

  • A large scale cohort study of 502,000 participants (age, 37-73 years) from the UK Biobank who spent a median of 2.5 hours (interquartile range, 1.5-3.5 hours) daily in outdoor light during the daytime.

  • Funding: None.

Key results

  • In cross-sectional analysis, greater time spent in outdoor light during the day was associated with:

    • lower risk of lifetime recurrent major depressive disorder (adjusted OR [aOR], 0.96; 95% CI, 0.92-0.98) and antidepressant use (aOR, 0.95; 95% CI, 0.92-0.98);

    • greater self-reported happiness (aOR, 1.45; 95% CI, 1.41-1.48);

    • lower neuroticism (incidence rate ratio, 0.96; 95% CI, 0.95-0.96); and

    • less frequent low mood (aOR, 0.88; 95% CI, 0.87-0.89) and anhedonia (aOR, 0.95; 95% CI, 0.93-0.96).

  • Furthermore, greater time spent in outdoor light during the day was associated with (aOR; 95% CI):

    • earlier chronotype (0.76; 0.75-0.77);

    • greater ease of getting up (1.47; 1.46-1.49);

    • fewer insomnia symptoms (0.96; 0.94-0.97); and

    • less frequent tiredness (0.81; 0.80-0.82).

  • Overall, longitudinal associations between time spent in outdoor light and mood, sleep and circadian-related outcomes later were consistent with the cross-sectional findings, but with smaller effect sizes.


  • Observational design.


Burns AC, Saxena R, Vetter C, Phillips AJK, Lane JM, Cain SW. Time spent in outdoor light is associated with mood, sleep, and circadian rhythm-related outcomes: A cross-sectional and longitudinal study in over 400,000 UK Biobank participants. J Affect Disord. 2021 Aug 27 [Epub ahead of print];295:347-352. doi: 10.1016/j.jad.2021.08.056. PMID: 34488088.  View abstract 

This clinical summary originally appeared on Univadis, part of the Medscape Professional Network.


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