August 21, 2009

Lack of Sunshine Inhibits Thinking For Depressed

A new study suggests that a lack of sunshine may cloud memory and other thinking or "cognitive" functions in some people with depression, Reuters reported.

Experts have often cited the association between sunlight exposure and mood.

One such example is seasonal affective disorder (SAD), which is a depression where symptoms shift with the seasons, usually arising in the late fall and winter and improving in sunnier months.

Researchers are now attempting to find out whether sunshine can affect thinking and memory.

A team from the University of Alabama at Birmingham studied the correlation between NASA weather data and cognitive-test scores among more than 14,000 U.S. adults age 45 and older that had taken part in a government study of the different factors for stroke risk.

Among those who had screened positive for depression, the test subjects that had been exposed to little sunshine over a two-week period most often had lower cognitive scores than those who lived in sunnier areas.

Impairments in memory and other cognitive functions were more than twice as likely to show up in depressed adults from the least sunny areas compared to those with more exposure to the sun.

However, the sunshine-cognition link was not noted in adults without depression.

The researchers acknowledge that the findings do not prove that a lack of sun impairs depressed people's thinking -- or that basking in the sun will improve the situation.

Lead researcher Shia T. Kent, a Ph.D. candidate at the Alabama University, told Reuters Health people should not take any drastic actions based on one study.

But sunlight might affect cognition through the same pathways it is thought to impact mood, Kent said. Since sun exposure helps regulate melatonin and serotonin levels that affect mood, they are suspected of playing a role in SAD and general depression.

Both melatonin and serotonin are also involved in cognition, according to several new studies.

Kent speculated that people who are more affected by sunlight exposure in terms of depression might also be more affected in terms of cognition.

The study, published in the journal Environmental Health, suggests that light therapy, which is a standard treatment for SAD, might improve depressed individuals' cognition.

Future studies of SAD patients, including those testing light therapy, should look at any potential effects on cognition, Kent noted.


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