About this time of year every year, people begin to feel... off. You might already be starting to get sick of hearing your friends' complaints about how down they are now that we're in the midst of winter. Chances are, at least someone in your circle has gone ahead and diagnosed themselves with seasonal affective disorder (SAD). This disorder has become such a part of our culture that it seems like everyone has it (or at least thinks they have it). But the true story about SAD — which is either the best or worst medical acronym, ever — is more complicated, even controversial, than you might realise.
First off, SAD as we know it colloquially isn't actually in the Diagnostic and Statistical Manual (DSM), a.k.a. the giant book that therapists use to make diagnoses. The idea of winter-related sadness has been around for centuries, but was only formally documented in medical research in 1984 as SAD, which was described as a "syndrome characterised by recurrent depressions that occur annually at the same time each year." Today, however, what most experts refer to as SAD is really a form of major depression "with seasonal pattern."
As with other forms of depression, the kind that seems to come and go isn't simply feeling down. Clinical depression — with or without a seasonal component — is a serious disorder characterised by loss of interest in things that were once pleasurable, loss of energy, changes in appetite and sleep habits, and, in its most serious forms, suicidal thoughts, explains Dan Oren, MD, who serves on the board of directors for the Centre for Environmental Therapeutics. Although anyone with major depression may have recurrent episodes, what we know as SAD is unique in that it seems to consistently return at around the same time every year, primarily in the winter.
The current prevailing theory is that a lack of sunlight during shorter winter days is at the root of the disorder, perhaps because it throws off the ebb and flow of our circadian rhythms. That may be because the hormonal changes we go through respond to external cues — including things such as sunlight — and includes the regulation of, among other things, the release of the neurotransmitter serotonin, which is related to mood regulation.
Some studies suggest that light-box therapy (possibly in addition to psychotherapy and/or medication) may be a helpful treatment, because it can potentially replace the sun as an external cue for our circadian rhythms. The thinking goes, without getting sunlight every morning, you need something else to keep those biological patterns on track.
However, despite the fact that many of us complain of "winter blues," far fewer of us have the clinically diagnosable version of SAD. Dr. Oren says that there hasn't been a good nationwide survey of SAD prevalence, but there's some evidence to suggest the number of people with the disorder may be different depending on the latitude of where they live. For instance, one study found that the prevalence may be as low as 1.4% in Florida and as high as 9% in New Hampshire.
"[Instead], what your friends are self-diagnosing themselves with may be a milder version [of SAD] that doesn’t qualify as major depression," Dr. Oren says. This milder change in mood may be much more widespread than full-blown SAD. But there are still plenty of unanswered questions: How many of us really do experience depressive symptoms during the winter every year?
Steven LoBello, PhD, at Auburn University at Montgomery, is one of the authors on a paper published earlier this year in Clinical Psychological Science that suggests that number is much smaller than you'd think. For the study, Dr. LoBello and his co-authors went through data from a national survey of over 34,000 people. The survey asked about all sorts of health-related things, but also asked people about the symptoms of depression — without explicitly saying anything about depression. The researchers correlated those scores with the time of year, participants' locations, and the U.S. Naval Observatory's measurements of daylight at the time of the survey.
What kind of pattern did they find? Well, actually, they didn't find any real pattern. Their results showed that, overall, about 5% of the survey respondents met the requirements for major depression, which is about on par with other estimates. But there was no difference in that number depending on the season or availability of sunlight.
"We thought we were going to be establishing the prevalence [of SAD]," says Dr. LoBello. "But we found the prevalence was zero."
This is where it gets complicated: Dr. LoBello explains that a fair amount (though not all) of the previous research into SAD was done by asking people a series of questions that make up the Seasonal Pattern Assessment Questionnaire (SPAQ). That includes questions such as, "To what degree does mood change with the seasons?" and, "At what time of year do you sleep least?"
In contrast, the data that Dr. LoBello used was collected using questions that ask specifically about the symptoms of major depression as defined in the DSM. For example, "How many days in the past two have you had trouble with sleep?" Or, "How many days in the past two weeks have you felt down, depressed, or hopeless?"
The distinction is subtle, but it's one that Dr. LoBello believes is vital: The self-reported nature of much of the previous research could have unintentionally inflated the number of people who actually have SAD symptoms. And that's a crucial issue when the questions are asking about a widely held cultural belief (that our moods get worse in the winter).
"If you ask people straight-up, 'Does your mood change with the seasons?' I think a lot of people are going to just say yes," says Dr. LoBello. "But it's a whole different matter to ask [how common specific] symptoms of depression are...in the fall."
Based on these findings, Dr. LoBello says he isn't sure SAD exists at all. And because his team looked specifically at depression symptoms, he's "pretty confident that, whatever it is, is not major depression."
Dr. LoBello isn't the only one poking holes in the SAD story: He points to a paper published in 2008 by a group of Norwegian researchers. In the northernmost parts of Norway, there is a so-called "dark period" in which "the sun does not rise above the horizon at all" and "there is only a dim light for a couple of hours during midday," the authors write. But after over a decade of research, there didn't seem to be much evidence of SAD — even in Norway. "Our findings consistently indicate that living in almost complete darkness for two months does not increase the prevalence of depression above the expected population level of depression in general," they write.
One issue may be in the way we exaggerate our feelings. We often say we're "depressed" when we're just feeling blah. Dr. LoBello explains that our moods fluctuate up and down naturally and can change every day. Depression, however, is persistent. You may feel crabbier during the holidays for plenty of reasons — the weather may be too gross for you to go outside to exercise or maybe planning your holiday travel (which includes the idea of seeing your family) may have you a little on edge, for instance. This stuff can feel unpleasant, but that doesn't mean what you're experiencing is seasonal depression.
The one thing everyone can agree on is that, as Dr. Oren puts it, "There is no diagnosis called 'holiday blues.'" The holiday season doesn't truly cause widespread clinical depression. Suicide rates do not increase during the winter months. And those who do experience SAD symptoms tend to feel their worst around January and February — not in December. (In fact, a small percentage of people report that their symptoms are most severe during the summer months.)
However, if you do feel off during the holidays, that's totally understandable, too. (And clinical depression may, indeed, be involved.) But even if it's not, your feelings are valid — you don't need a diagnosis for that. It's okay to just be a grinch.
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