Sunshine Increases the Cognitive Performance of Depressed Study Subjects
While researchers have long known of an association between sunlight intensity and mood, scientists now know that sunlight affects how effectively depressed people think, as well.
Blue skies lift our spirits while somber days dampen the mood; and for people with seasonal affective disorder, levels of sunlight seem to induce a cyclical disorder of depressive symptoms. Sunlight affects the way we feel deeply, but does it also affect the way we think?
That’s a question researchers at the University of Alabama at Birmingham School of Public Health wanted answered.
The researchers knew that sunlight affected the neurochemicals melatonin and serotonin in areas of the brain that can affect emotion and mood and that these same areas play a role in cognition. The researchers also knew that light box therapy can help to alleviate depressive symptoms and wondered if light therapy might also help to alleviate cognitive declines.
Linking Sunshine and Smarts
The researchers used data collected in a large scale longitudinal study of stroke risk factors. In this study, named the REGARD Study, more than 16 000 participants submitted to telephone interviews that included a brief 6 question cognitive screening test. Each study subject was also asked about their experience of depression.
The Alabama at Birmingham researchers then used NASA ground and weather satellite data to determine the intensity of sunlight on the day, and 2 weeks preceding the day, of the telephone interview, for each REGARD subject’s immediate geographical area.
The researchers then looked at how sunlight intensity affected cognitive performance.
They found sunlight did not affect REGARD subjects that did not admit to depression, but that REGARD subjects who admitted to depression and who lived in areas that had experienced high levels of recent sunshine performed better than depressed subjects living in areas that had experienced less recent sunshine; the more sunlight exposure, the better the cognitive performance.
Seasonal differences were controlled for.
The researchers claim to be the first scientists to test for the correlation between cognitive performance and sunlight exposure in depressed subjects.
The full study data can be found in the journal, Environmental Health