Time of year and weather conditions don't have much influence on depressive symptoms. Getting depressed when it's cold and dreary outside may not be as common as believed.
That's not to say clinically diagnosed seasonal affective disorder (SAD) is not real, the authors note, but instead that people may be overestimating the impact that seasons have on depression in the general population.
The scholars analyzed surveys from a sample of 556 community participants in Iowa and 206 people in western Oregon. Participants completed self-report measures of depressive symptoms multiple times over a period of years. These data were then compared with local weather conditions, including sunlight intensity, during the time participants filled out the reports.
"It is clear from prior research that SAD exists," said lead author David Kerr, assistant professor in psychology at Oregon State University. "But our research suggests that what we often think of as the winter blues does not affect people nearly as much as we may think. People are really good at remembering certain events and information. But, unfortunately, we probably can't accurately recall the timing of day-to-day emotions and symptoms across decades of our lives. These research methods are a problem."
In one study, some 92 percent of Americans reported seasonal changes in mood and behavior, and 27% reported such changes were a problem. Yet the study suggests that people may be overestimating the impact of wintery skies.
"We found a very small effect during the winter months, but it was much more modest than would be expected if seasonal depression were as common as many people think it is," said Columbia University researcher and paper co-author Jeff Shaman. "We were surprised. With a sample of nearly 800 people and very precise measures of the weather, we expected to see a larger effect."
Kerr believes the public may have overestimated the power of the winter blues for a few reasons. These may include awareness of SAD, the high prevalence of depression in general, and a legitimate dislike of winter weather.
"We may not have as much fun, we can feel cooped up and we may be less active in the winter," Kerr said. "But that's not the same as long-lasting sadness, hopelessness, and problems with appetite and sleep – real signs of a clinical depression."
According to Kerr, people who believe they have SAD should get help. He said clinical trials show cognitive behavior therapy, antidepressant medication, and light box therapy all can help relieve both depression and SAD.
"Fortunately, there are many effective treatments for depression, whether or not it is seasonal," he said. "Cognitive behavior therapy stands out because it has been shown to keep SAD from returning the next year."
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