眾所周知，日照與情緒息息相關，最明顯的例子就是季節性情感障礙——抑郁癥的一種，其癥狀隨著季節的變化而不同，通常是患者病情在秋冬季節加重，而光照多的季節得到緩解。但是，光照能影響人們思考和記憶，卻是個新話題。根據一項最新的研究顯示，經過兩周的觀察，生活在光照時間短條件下的抑郁癥病人，其認知能力低于在光照時間較長氣候生活，有同樣病癥的患者。

A jogger runs at the foothills of the Canadian rocky mountains near Calgary, Alberta November 20, 2007.

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

There is a well-known association between sunlight exposure and mood, the clearest example being seasonal affective disorder (SAD) -- a form of depression in which symptoms shift with the seasons, usually arising in the late fall and winter and improving in sunnier months.

But little is known about whether sunshine can affect thinking and memory.

For the new study, researchers at the University of Alabama at Birmingham looked at the correlation between NASA weather data and cognitive-test scores among more than 14,000 U.S. adults age 45 and older. All had taken part in a government study of stroke risk factors.

The researchers found that among people who had screened positive for depression, those who had been exposed to little sunshine over a two-week period tended to have lower cognitive scores than their counterparts who lived in sunnier climes.

Depressed adults from the least sunny areas were more than twice as likely to have impairments in memory and other cognitive functions as those with the greatest sun exposure.

The sunshine-cognition link was not seen in adults without depression, however.

The findings, published in the journal Environmental Health, do not prove that a lack of sun impairs depressed people's thinking -- or that basking in the sun will improve the situation.

"You obviously don't want to take any actions based on one study," lead researcher Shia T. Kent, a Ph.D. candidate at the Alabama university, told Reuters Health.

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

Recent research suggests that melatonin and serotonin are also involved in cognition.

"It may be that people who are more affected by sunlight exposure in terms of depression are also more affected in terms of cognition," Kent speculated.

The findings also raise the possibility that light therapy, which is a standard treatment for SAD, might improve depressed individuals' cognition as well.

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

相關閱讀：

你容易得抑郁癥嗎？

研究：抑郁女性更渴望性愛

調查：白領更易患抑郁癥

研究：生育、厭食和抑郁影響女性性生活

Vocabulary:

bask: 曬太陽

cognition: 認知

（英語點津 Helen 編輯）