Is Seasonal Affective Disorder Real?

New research on SAD questions the connection between sunlight and depression

seasonal affective disorder, health and wellness, mental health, seasonal illness, depression, winter, sunspot, light therapy, duluth

Illustration by Darren Gygi

For nearly 30 years, mental health professionals have officially recognized seasonal affective disorder, or SAD, as a subset of depression. In addition to depression’s usual feelings of hopelessness, SAD often is diagnosed by additional symptoms such as low energy, oversleeping, a craving for carbs, weight gain, and even a heavy feeling in the limbs. Though the medical community hasn’t identified the specific cause of SAD, most theories revolve around reduced levels of sunlight triggering changes in key mood regulators, serotonin and melatonin, and disrupted circadian rhythms. One of the treatments for SAD involves patients sitting close to a light therapy box designed to mimic bright outdoor light.

But as the northern hemisphere’s shortest day of the year fast approaches, recent research has called our thinking about SAD into question. Every year, the Centers of Disease Control conducts health behavior surveys, and a group of researchers used the results of some 35,000 Americans queried to study SAD. They looked at both how the incidence of depression varies by season, as well as the rates of depressive symptoms at northern, low-light latitudes compared to those closer to the equator. In reviewing responses from the general population, as well as the subset of respondents who identified as depressed, the researchers were surprised to find neither an increase in depression during winter, nor a greater prevalence of depression among those in northern latitudes. 

Results of prior studies on how depression relates to seasons and latitudes have been mixed, as mental health disorders can be difficult to study. In the case of SAD research, there are challenges with how questions are being asked as well as confirmation bias, the cultural expectation that some form winter-based depression exists. The new study doesn’t conclusively and definitively deny SAD, but leaves open the possibility that the disorder may affect a tiny portion of the population or that it may be a different form of mood disorder entirely. 

Regardless of the debate among researchers, Minneapolis psychiatrist Dr. Craig J. Vine of Psych Recovery, a clinic that specializes in depression and anxiety, says that patients regularly tell him their depression worsens in winter. Because the treatment for SAD consists of doing things that are beneficial to most people regardless of their mental health—spending time outside, exercising, socializing, eating well, sleeping well—the results of the recent study haven’t changed his recommendations. “I have patients who follow SAD treatment recommendations and say they feel better, so why would I argue and say, No, you aren’t feeling better?” he says. “If you feel worse in the winter, let’s go ahead and do something about it.” 

Duluth resident Sue York is one patient who swears by light therapy, exercise, nutrient-rich food, and socializing to keep her symptoms at bay. In fact, she’s so enthusiastic about treating SAD that she inspired her twin sister, Katherine, to move to Duluth from California to co-found the SunSpot, a light therapy business. They bought a bus, retrofitted it with full-spectrum lights and comfy seating, and stocked it with healthy snacks. They charge $5 for 30 minutes on the bus. “We want to make the SunSpot be something people want to get to, because when you’re depressed you don’t even want to go anywhere,” Sue says.

While such activities are likely to benefit most people, regardless of their mental state, it would be helpful if SAD could be more accurately defined, contends Steven LoBello, a professor of psychology at Auburn University at Montgomery who worked on the recent CDC data analysis. “The goals of a person in clinical practice are different than my goals as a researcher,” he says. “I’m trying to get at a truth of the matter and the clinician is trying to relieve suffering, and if you can do that without causing too much harm and it’s safe and effective, they may not ask too many questions beyond that. But I feel like sooner or later someone needs to try to get at the truth.”