In 1987, seasonal affective disorder, or SAD, was written into the third edition of the Diagnostic and Statistical Manual of Mental Disorders (DSM). Since then, the mood disorder marked by the onset of winter has seeped into our collective conscious and culture. I've certainly taken it to heart. At the slightest drop in temperature, my outlook on life goes from bleak to paralyzingly bleak; anything not necessary to survival doesn't appear worth leaving my apartment for. I find myself thinking, to remain hopeful in my lowest moments, that spring and summer will be better. When that doesn't work, I passively browse Amazon for solutions: I've been a click away from ordering a combination high-intensity LED light and visor.
(I've noticed, too, that my pet chameleon, Drake—who is sensitive to the sun's variations and cranes his body like a sail to soak up as much light as he can before it goes dark at 5 PM—is affected by winter. As it gets colder and darker, his normally slow pace is reduced to what could barely be considered movement; he parks his pudgy green belly on the branch below his heat lamp for hours until he decides to go elsewhere to sleep, which is cute but concerning.)
Just in time for spring-like weather, a new study on seasonal affective disorder, published in Clinical Psychological Science, however, casts doubt on the diagnosis and my scientifically sound observations about my lizard. Researchers at Auburn University at Montgomery analyzed data from a 2006 survey conducted by Centers for Disease Control and Prevention (CDC). That year's data uniquely contained responses to questions from the Behavioral Risk Factor Surveillance System (BRFSS), which gathers information on health risk behaviors, including depressive symptoms. Using a subset of 34,294 American adults who took the BRFSS throughout that year, the researchers were able to track any seasonal patterns in the responses.
Because seasonal affective disorder is often linked to light exposure, they looked to see whether respondents in the northernmost regions of the country (with low light exposure) reported being depressed at a higher rate. They also looked to see if respondents who answered the questionnaire during the winter more frequently reported being depressed. They found no indication that either light or season affected the responses.
"The idea that depression occurs along with seasonal changes or worsens in winter appears to be a well entrenched folk theory," writes the study's lead researcher, Dr. Steven LoBello. "The findings cast serious doubt on major depression with seasonal variation as a legitimate psychiatric disorder. In clinical cases of recurrent depression, stressful life events associated with episodes may coincidentally co-occur with seasonal changes for some people."
Scandalized, I called up Dr. LoBello and asked him why he was trying to destroy my worldview. "This was a research project by my graduate student, Megan Traffanstedt," he clarified, before explaining that he didn't necessarily set out to lay seasonal affective disorder to rest. "We had the opportunity with [the CDC] data set to analyze this inordinately high number of people who had taken this depression scale. We thought this data set would be perfect to see what seasons actually contribute to the prevalence of depression."
In the study, Dr. LoBello concedes that if seasonal affective disorder is actually rare in the population—rather than afflicting basically everyone you talk to from November through March—he may not have been able to detect it using the survey data. "One explanation for our findings could be that seasonal affective disorder is rare," he said, "but I don't think that's a very good explanation because nobody says that this is a rare disease." The American Academy of Family Physicians reports that SAD affects four to six percent of people in the US annually, with another ten to 20 percent of people possibly suffering from a "mild" version of the disorder.
Much of the previous research on seasonal affective disorder was determined using Seasonal Pattern Assessment Questionnaire (SPAQ), though, and Dr. LoBello asserts that this is a problematic tool because it "relies on recall of past depressive episodes to establish cases of SAD."
"The SPAQ has a set of about six questions that ask you things like, 'Does your mood change with the seasons?' or 'Does your appetite change with the seasons?' Then, if you answer yes to those questions, it will ask you, 'What months do you feel the worst?'" he explained. "Those are incredibly leading questions. I don't know anyone whose mood doesn't change from season to season or from day to day, but that doesn't mean they're depressed. I don't think this instrument maps depression very well."
Dr. LoBello's study, on the other hand, used data from eight questions commonly used to screen for major depression. The respondents, who were just taking a routine survey, weren't primed to think about seasonal affective disorder, nor did they have any expectation biases. That's why Dr. LoBello thinks it's time to give up our mass delusion. "We just didn't find any relationship between latitude or season to depression," he explains. "Depression is a recurrent disease. It could possibly occur in two consecutive winters by chance—and that, coupled with the cultural expectation [of seasonal affective disorder] could be enough to convince someone that their depression is seasonal."
"Being depressed during winter is not evidence that one is depressed because of winter," the study concludes. Fine!