August 5, 2009
How does sunlight exposure affect cognition? It affects both regulation of the hormones serotonin & melatonin and blood flow in the brain, researchers say.
A lack of sunlight is associated with reduced cognitive function among depressed people. A free access report published Jul 28 in Environmental Health(1) explains how US researchers used weather data from NASA satellites to measure sunlight exposure across the country, and linked this information to the prevalence of cognitive impairment in depressed people.
The team, led by Shia Kent at the University of Alabama, Birmingham, used cross-sectional data from 14,474 people in the NIH-NINDS-funded REGARDS study, a longitudinal study investigating stroke incidence and risk factors, to study associations between depression, cognitive function and sunlight.
"We found that among participants with depression, low exposure to sunlight was associated with a significantly higher predicted probability of cognitive impairment. This relationship remained significant after adjustment for season,” says Kent.
“This new finding that weather may not only affect mood, but also cognition, has significant implications for the treatment of depression, particularly seasonal affective disorder."
Kent and his colleagues speculate that the physiological mechanisms that give rise to seasonal depression may also be involved in sunlight's effect on cognitive function in the context of depressive symptoms.
Cognitive function was assessed by measurement of short-term recall and temporal orientation. As well as regulating the hormones serotonin and melatonin, light has been shown to also affect brain blood flow, which has in turn been linked with cognitive functions.
The researchers write, "Discovering the environment's impact on cognitive functioning within the context of seasonal disorders may lead not only to better understanding of the disorders, but also to the development of targeted interventions to enhance everyday functioning and quality of life."
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1. Article: “Effect of sunlight exposure on cognitive function among depressed and non-depressed participants: a REGARDS cross-sectional study,” Environmental Health, Jul 28, 2009 by Kent ST, et al. To read the full text article free in BioMed Central, click here
Source: BioMed Central news release, Jul 27, 2009
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