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Psychology-community debates about whether seasonal depression exists don't do much for patients who need mental-health care

A number of years ago, I was lucky enough to head out on a month-long trip to southeast Asia. It was late February, in the middle of another bleak Toronto winter and I was buoyed by the anticipation of adventure and, especially, sunshine. I was also able to observe, before I left, how those around me were coping with being cooped up in the cold. The clear answer was not well.

I felt particularly compassionate toward a friend-of-a-friend who rejected all overtures at optimism. She was sick of the heavy grey skies and her itchy black clothes, envious of those with more money to spend since, in the winter, that means more opportunities to leave the house. She was unpleasant, a total grouch. Her attitude filled me with a sense of relief – not just that I got to spend a few weeks away from sidewalks scattered with dog poopsicles, but that sinking into a stubborn low mood at this time of the year didn't appear to be a personal failing.

Since then, I've sensed a resigned solidarity in the winter months. I appreciate my fellow sufferers' effort to squeeze a bit tighter on the streetcar, so that others can get home, too; to look away to allow a stranger dignity as the snot drips off their nose; to dust off the chip crumbs and visit a friend who is just as unwilling to put on real pants as I am. We're all in this together.

That solidarity was challenged, though, by a set of research papers I recently came across while listlessly googling "winter depression." It seems that since 2016, a group of researchers in Montgomery, Ala., have been arguing that a "seasonal modifier" for depressive episodes isn't a "valid construct." According to Megan Traffanstedt, Sheila Mehta and Steve LoBello of the psychology department at Auburn University, depression is unrelated to latitude, season or sunlight. Moreover, the idea that it might be is an age-old "folk theory" that has infiltrated real medicine.

This got my back up immediately: Aside from contradicting my own experience, the researchers' use of the phrase "folk theory" seemed like code for "it's all in your head," or at least "doctor knows best." Then again, they're medical professionals and I'm not, so I tried to approach their research with an open mind.

Published in Clinical Psychological Science, their paper begins with a criticism of seasonal affective disorder. SAD, as it's commonly known, is a concept that entered the mental health lexicon in 1984, when a National Institutes of Health researcher named Norman Rosenthal posited that cold weather often led to changes in regular activities (such as eating, sleeping and socializing) that then negatively affected mood.

The idea and supporting research gained traction, and three years later, the American Psychiatric Association (APA) revised its definition of major depressive disorder in the Diagnostic and Statistical Manual of Mental Disorders (DSM), the definitive mental-health-care guide on this side of the Atlantic.

SAD wasn't included on its own, but the APA introduced a subtype of depression defined by seasonal change. Patients could now be diagnosed with "major depressive disorder with seasonal pattern" (MDD-SP), a similar classification to postpartum depression, which is officially known as "major depressive disorder with peri-partum onset." Unlike SAD, MDD-SP isn't defined as happening in the winter, just recurrent in the same season over time.

According to the Auburn University researchers, the transition from the idea of SAD to the DSM-approved MDD-SP diagnosis was done without proper scientific rigour. Their own study – a telephone questionnaire administered to over 30,000 American adults – showed no meaningful correlation between season and depressive episodes. As such, they argued that the APA should consider discontinuing the seasonal subtype.

Their original paper was quickly rebutted. Michael A. Young of the Illinois Institute of Technology took a swipe at the researchers' "conceptual and methodological issues," to which Dr. LoBello responded by further discounting the "folk psychology" of the "winter blues." The back-and-forths went on well into last year, and as the citations, acronyms and pages piled up, it began to seem like academic navel-gazing that didn't concern me.

On the other hand, the "folk theory" thing still nagged.

I don't care about SAD or MDD-SP as labels, but I do care about discounting the way people understand their own lives. Anyone who has navigated through medical bureaucracy while caring for a loved one, or while sick themselves, knows that it's an exhausting and frustrating experience. It's one made worse if the professionals at hand are condescending, which isn't always the case but certainly happens – take postpartum depression (or depression with peri-partum onset, if you prefer), regularly dismissed as just another form of women's "hysteria" until at least the late 19th century.

I wanted to figure out what all of this sniping over labels meant for patients, especially those trying to cope with depression in the winter. I added "Canada" to my Google search term and ended up talking to Scott Patten, a professor of psychiatry at the University of Calgary.

In 2016, Dr. Patten and his team published their own paper about seasonal depression. It used data from 10 Statistics Canada surveys, combining the experiences of around 500,000 people, and appeared in an epidemiological journal put out by the Cambridge University Press. It also got way less attention that the Auburn University paper, which was mentioned in an article in Scientific American. "I think it's because they're saying something provocative," Dr. Patten says. "I personally have more confidence in our data."

What their data shows is a clear pattern – twice as many people reporting depression from November to March than from May to August. "That's quite a dramatic seasonal difference," Dr. Patten says, similar to the differences between the sexes (women are twice as likely to experience depression than men) and between those who have jobs and the unemployed. Far from arguing that seasonal depression be eliminated as a concept, the Calgary team wants to do further research to determine whether sufferers should be categorized as "high risk," with greater access to services when they're most likely to need them.

Dr. Patten says there's a good reason psych professionals are fixated on SAD. For many years, there was a less-than-scientific assumption that SAD was caused by changes in the duration of sunlight at different times of the year. This was exciting because it's generally agreed upon that the circadian system – or how our sleep and wake cycles coincide with the rise and fall of the sun – is somehow, albeit mysteriously, tied to mood.

Disruptions in circadian rhythms are implicated in depression and addiction risk in teenagers (who are naturally somewhat nocturnal, but required to be at school by 9 a.m.). They're also of interest in the mood swings of shift workers (whose livelihood demands working against natural sleep-wake rhythms).

The relationship between sleep – whether too much or too little – and depression is fascinating to many, including me. In 2011, after years of sleeping-pill use that trashed my mood, I underwent drug-free behavioural therapy for insomnia and ended up with a much better outlook. Waking up in the middle of the night is a "classical symptom of depression," Dr. Patten says; one reason that a connection between light and SAD seemed to make sense.

Light therapy for the winter blues became the go-to treatment, sometimes without medical intervention – so-called SAD lights are now available everywhere, from Amazon to Shoppers Drug Mart. Alas, there is one commonality between the Calgary and Montgomery research, which is that neither "photo period" (i.e., length of daily sunlight) nor latitude seemed to affect incidents of depression.

That doesn't mean light is totally irrelevant, Dr. Patten says, but that perhaps other seasonal factors – such as diet, reduced exercise or basic dislike of the cold – are more significant. It's complicated: In 2016, the Canadian Journal of Psychiatry said that cognitive behavioural therapy, anti-depressant drugs and, yes, light therapy were all effective treatments for a substantial number of patients. That said, no single treatment is infallible for all.

"Depression is almost always multifactorial," he says. "You cannot point towards a single factor and say this always causes depression, or this would be enough to cause depression in anyone even without any other risk factors."

Mood is also very personal. The original SAD researcher, Dr. Rosenthal, was driven by a need to explain why his own changed so much after moving from South Africa to New York. At his psychiatric practice, Dr. Patten says he's had a "totally unscientific observation" that emergency-room visits and referrals for depression go up in the winter, creating wait lists that don't get dealt with until summer.

Feeling down in February doesn't necessarily equal clinical depression, but dismissing lived experience out of hand is arrogant, and could be dangerous. It's 25 degrees Celsuis in Montgomery as I write this; perhaps the researchers can dismiss winter depression because they don't know what it's like to feel it in their bones.

Anecdotes aren't scientifically provable, but that doesn't make them less real. If the "folk theory" of the winter blues makes you feel less alone as this cold season wraps up, take heart. Spring is coming.

In the meantime, nestle yourself into a nice, warm scarf and summon up the energy to ask for a little help.