Notoriously overcast and drizzly all year round, Seattle turns especially dour in the winter, when unrelenting darkness descends on the Pacific Northwest. Living through a Seattle winter is a true test of someone’s ability to function without sunlight — and it’s not a test that every resident of the Emerald City passes. For Steven, who asked that his last name not be used, relocating there at the age of 22 manifested in a 13-year struggle with seasonal depression that ended only when he moved to Mexico.
“I didn’t bother looking for [a diagnosis] until maybe eight years in,” he said. “I just figured this is life. My depression cleared up during the sunny months and returned with the clouds.”
Some 30 years after it was first identified, seasonal affective disorder, a form of depression related to a change in seasons, continues to be an often-misunderstood condition. The disorder, which ranges in terms of severity, can strike people whether or not they’re otherwise prone to depression and may affect up to 10 percent of the population in certain, light-deprived geographic regions. While there’s obviously correlation between the darker days of the winter months and the onset of depression — one that lifts during spring and summer — researchers are still batting around hypotheses to explain exactly what’s happening to those who get SAD when the days get short.
Jeff Janata, a psychologist and division chief of psychology at UH Cleveland Medical Center, says that SAD is often perceived as a product of dynamic brain activity in response to light. “A common theory is that melatonin, which is a brain chemical that helps us feel sleepy, is triggered by darkness,” he said. “With SAD, the increased exposure to that darkness with the shorter days of winter means we’re producing more melatonin and therefore getting sleepier and more lethargic.”
It’s a reasonable enough explanation: A lack of sunlight might be lulling some of us into drowsiness by throwing our circadian rhythms out of alignment. But melatonin’s influence in the brain doesn’t stop there. “Melatonin is also related to serotonin activity,” Janata said. “And that’s related to mood regulation. So SAD is really a multi-module model in terms of what’s going on.”
But ideas about what’s going on in the brains of SAD patients change all the time.
Recent research exploring how birds and small mammals respond to changes in daylight has shown that melatonin may also make its way into the hypothalamus region of the brain and disrupt the production of active thyroid hormone, which help balances mood and behavior.
It’s also possible that the development of SAD also has something to do with a person’s chronotype, meaning when they naturally prefer to sleep during a 24-hour period (i.e., whether you’re a night owl or a morning bird). People who are prone to “eveningness,” or the tendency to go to bed and wake up late, may be more susceptible to SAD’s effects.
One 2018 study even established a link between SAD and eye color. Well, potentially, because brown eyes don’t absorb as much light as blue eyes, making amber-eyed people more vulnerable to darkness-related deficiencies. A questionnaire circulated among 175 students at the U.K.’s University of South Wales and Girne American University in Cyprus found that those with brown eyes were more likely to have SAD, among other mood disorders.
The line between lethargy, depression and the pall of increasing darkness is often blurry. For Steven, Seattle’s winters brought on a case of SAD that weighed down his whole life. “It trapped ‘me’ away for eight months per year, and something else was in control of my life,” he said. “I remember being in the back of my own mind, screaming the words I wanted to speak, struggling to make my body move, and it wouldn’t respond.”
“I felt completely isolated from everyone because of this, and I was completely incapable of reaching out. After a few years, I just gave up. I knew that nothing I could do would work, and I just waited until the sun came out and I could feel a little normal again.”
In some ways, Janata says, SAD may be a normal seasonal adaptation, akin to hibernation. “It makes some sense with evolutionary theory,” he said. “It used to help with survival if we slowed down in the winter, conserved our resources, gained some weight and slept a lot.”
A 2018 study from the University of Glasgow took this theory of energy conservation further, drawing a connection between having SAD and being a woman of reproductive age. Researchers found that women were 40 percent more likely than men to exhibit seasonal depression, and that the disorder was more severe during the child-bearing years. It’s possible, researchers surmised, that SAD is an amplified result of a biological drive to shield off-spring from harsh conditions.
Despite having an external and obvious stimulus in the sun, SAD remains one of the least-understood diagnoses in mental health. While work is being done, it receives only a fraction of the attention given to more pervasive disorders. “Part of the reason for that is lack of research,” said Richard Catanzaro, a chair of psychiatry at Northern Westchester Hospital, near New York City. “There’s just not a ton of money being spent on it. It’s not commonly seen on the acute end of psychiatry. Few people are being admitted for it.”
Catanzaro says experts still aren’t quite sure whether SAD is genetic, or if someone who hails from a sunny climate is more vulnerable to seasonal depression than a person who’s spent their entire life riding out gloomy weather. “The thing we can say with some degree of accuracy is that it occurs more in northern latitudes as opposed to southern latitudes,” he said. In Florida, SAD might account for 1 percent of mood disorders. In Alaska, Toronto or Maine, it’s closer to 10 percent.
Because of the sun-exposure factor, popular treatments have often included vitamin D supplementation, the idea being that decreased sunlight means decreased levels of the vitamin, which can influence mood and well-being. “There’s not what I could call robust research showing that it’s curative,” Catanzaro said. “It is related to low mood and can’t hurt, but treatment with light therapy or antidepressants is most effective.”
Light therapy is what most presume it to be: exposure to artificial light to make up for what the sun isn’t producing. Those suspected of having SAD are typically told to sit in front of a light box for 30 minutes in the morning to prevent melatonin from running wild. While light therapy poses limited risks (although there are a few), some people opt for medication instead. “People don’t have the quote-unquote time for it,” Catanzaro said. “Me, I’d take the light box. But some people need both.”
Some people with SAD also try cognitive behavioral therapy, a results-oriented treatment approach centered on changing disordered patterns of behavior and thinking. In the case of SAD, the goal is to shift focus away from gloom and darkened moods associated with the winter months. When it comes to choosing CBT vs. light therapy, there’s no consensus among researchers yet. One 2015 University of Vermont study examined the effectiveness of CBT vs. light therapy to treat SAD. The next winter after the experiment took place, participants from both treatment groups reported comparable SAD relief. Two winters later, however, 27 percent of participants who’d been in the CBT group were still struggling with SAD, compared to 46 percent of the light therapy group, who also reported more severe depression symptoms.
There are also people who may not need (or benefit from) either treatment — because it’s unlikely they actually have the disorder. Sometimes, the SAD label is applied too readily and the diagnosis becomes a catch-all for anyone who has the winter blues. In one study, of 119 SAD patients interviewed two to 12 years following diagnosis, 59 percent were in remission.
“There are other things that happen in the winter besides lack of sunlight,” Catanzaro said. “People aren’t necessarily as social because it’s cold out. Some people have seasonal work and aren’t as busy. They don’t exercise as much. Some people focus on getting depressed during winter and don’t remember there were two weeks in July when they didn’t get out of bed.”
According to Janata, anyone can benefit from refusing a wintertime quarantine. “Some people would benefit from taking up winter sports, or just spending more time outdoors,” he said. “Even curling up under a blanket in front of a fire is a coping strategy.” Activity and light, whether natural or artificial, can stave off or help mitigate the effects of a blighted mood.
Janata also believes the growing field of neuroscience may bring us new and compelling insight into the onset and progression of SAD. “Our view of depression will broaden significantly,” he said, and SAD is one of many disorders that will benefit. These biological factors are perpetually being mapped out in the lab. Researchers have expressed interest in ZBTB20, a receptor protein in the hippocampus that could be a “candidate gene” for the disorder. Another study found that personality traits like neuroticism and inhibited sociability might make SAD more likely.
In the meantime, those hit hardest by SAD may find themselves taking any measures necessary to brighten their moods. For Steven, who had tried light therapy, medication and even hypnosis with only mixed results, that meant leaving Seattle and not looking back. “I took my savings and moved to Mexico,” he said. “I’ve been here a few years now and no trace of SAD. Life is normal again. I’m me 100 percent of the time.”