Duane Hoffmann / msnbc.com
By
msnbc.com contributor
updated 8/5/2009 8:28:10 AM ET 2009-08-05T12:28:10

On bright summer days, Dawn Staudt-Vanek feels energetic and mentally sharp. But when the clouds come out, she loses her zip and her brain turns sluggish.

“I’m not depressed, exactly,” says the 51-year-old nurse from San Jose, Calif. “But I have no energy and I can’t focus. It’s hard to get up in the morning and my brain seems to have slowed down. It’s hard to even get myself to the gym.”

Scientists have long known that the shortened days of winter can wreak havoc on mood. A new study shows that some people are more mentally nimble on sunny days, but have duller brains on cloudy days, regardless of the season. The findings add to mounting evidence that the weather affects how well we think and respond.

The latest study, conducted at the University of Alabama at Birmingham, found that people were almost three times as likely to have impaired cognition after gloomy weather compared to those in sunny climes, if they were also experiencing some symptoms of depression.

For the new investigation, researchers scrutinized data on 16,800 Americans who were participating in a national study on stroke. Everyone in the stroke study had been interviewed over the phone and asked a series of questions to determine whether they were depressed.

The study participants were also given a quick test for cognition. At the beginning of the test they were told three words — “table, apple, penny” — and then asked to repeat the words back to the interviewer, explains the study’s lead author Shia Kent. Next they were asked several orientation-type questions, including what day of the week it was, what month and what year. After they answered those questions, they were asked to recall the three words they’d initially been asked to repeat.

To determine whether weather might be affecting mental agility, the Kent and his colleagues turned to NASA, which has day-to-day information on how brightly the sun is shining at various locations around the country. Then, after accounting for the role of the seasons, the researchers correlated each person’s cognition and mood scores against sunshine levels in the two weeks prior to the cognition and depression tests.

While the connection between cognitive impairment and dreary days was found only in depressed people, it wouldn’t take much of a leap to extend these findings to others, experts said.

“The cognition test was fairly crude,” says Robert DeRubeis, a professor of psychology at the University of Pennsylvania. “This test is meant to pick out people with problems that would be noticeable in daily life, not just by the person, but by others. It’s not designed to detect subtle, and even not so subtle, changes in our verbal facilities or quickness of response, or any of the things we all prize and count on in our jobs.”

Sun, clouds affect some people more
The most likely scenario is that there are people who are exquisitely sensitive to the weather, says Dr. Alan Manevitz, a psychiatrist at New York-Presbyterian Hospital/Weill Cornell Medical Center. “And when there’s excessive gloominess, they seem to experience something like a mini cycle of Seasonal Affective Disorder,” he adds.

While August’s usually bright days can lift mood and sharpen mental acuity, when the weather turns cloudy, there is a simple fix, says Manevitz: a a light box. The devices which blast broad-spectrum light as bright as a sunny day have been shown to help people who are affected by SAD.

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A report published in 2006 used functional MRIs to look at the effects of broad spectrum light – which is similar to daylight. The Belgian researchers found that as soon as people were exposed to bright light, brain activity sparked more strongly. When the light was taken away, brains became less energized.

A year later, the same group of researchers used fMRI machines to look at the impact of different wavelengths of light. They found that brighter green light quieted regions of the brain involved in working memory and mental alertness. Blue light had the opposite effect.

It all makes sense in terms of how we evolved, says DeRubeis. “In evolutionary terms, we were originally called upon to do the most taxing tasks during the day, so it makes sense that sunlight would serve as a signal to the brain to perk up so it could handle challenging things,” he explains. “And then it would make sense not to waste energy at night since nothing much happens after dark.”

So, does this mean that many of us might be smarter if we moved from places plagued by gloomy weather, like Seattle, to sunny climes like those found in Phoenix?

“We don’t yet know if living in a climate that consistently bombards you with light will improve cognitive function," says DeRubeis. “But there’s good evidence from the mood research front that visiting such a place and getting away from a gloomy place for a stretch of time is likely to have a good impact.”

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