A new large-scale survey of U.S. adults did not find higher levels of depressive symptoms during winter months or at times of reduced sun exposure, questioning the existence of seasonal affective disorder (SAD).
The Auburn University at Montgomery findings, published in Clinical Psychological Science, a journal of the Association for Psychological Science, provide no evidence that depressive symptoms vary seasonally.
To find out if depression spiked in winter, researchers examined data from a 2006 survey of 34,294 participants ranging from age 18 to 99 who were queried about their health using a common diagnostic tool (the personal-health questionnaire [PHQ-8]). Participants were asked how many days in the previous two weeks they’d experienced symptoms of depression.
Researchers also used geographic-location data to obtain season-related measures, including the actual day of the year people felt depressed, their latitude, and the amount of sunlight they’d been exposed to.
The results showed that respondents surveyed during winter months or at times of reduced sun exposure did not have noticeably higher levels of depressive symptoms.
Further, researchers found no seasonal differences in symptoms when they looked at a subsample of 1,754 participants who scored within the range for clinical depression.
“The findings cast serious doubt on major depression with seasonal variation as a legitimate psychiatric disorder,” the researchers concluded in the study.
However, since conditions with so-called “low base rates” — the rate at which something normally occurs — are difficult to detect in large-scale studies, researchers note it’s possible that major depression with seasonal variation exists in a small subset of the population.
“Mental-health professionals who treat people with depression should be concerned about their own and their patients’ accurate conceptions about the possible causes of depression,” says senior author Steven LoBello, PhD, professor of psychology at Auburn University at Montgomery, Ala. “Pursuit of treatments based on false causes is unlikely to lead to rapid and durable recoveries.