The Difference Between Seasonal Affective Disorder and Major Depression
Affecting about 5 percent of American adults, seasonal affective disorder (or SAD) is a form of major depressive disorder (MDD) that occurs in predictable, seasonal patterns during certain months of the year. While some people experience symptoms of SAD during the summer months, it’s far more common during the fall and winter months. For most people with SAD, depression symptoms start in late fall or early winter and dissipate by spring and summer.
While it is typically characterized by winter depression, it’s not the same as the “winter blues” — and it’s also not just major depression that happens to occur randomly when it’s cold outside. To help you better understand SAD’s unique symptoms and risk factors — and, even more importantly, the treatment options — we spoke to two experts. Here’s what they want you to know.
What are the symptoms of SAD?
Since SAD is a type of major depressive disorder, the symptoms can look similar. You might notice changes in your mood — such as sadness, hopelessness, numbness, or irritability — along with changes in appetite and energy levels, loss of interest in activities you typically enjoy, or, in severe cases, suicidal ideation.
While SAD presents some of the same biological and emotional changes as general depression, Harry Brandt, chief of psychiatry at the University of Maryland-St. Joseph Medical Center, says it usually manifests a bit differently than MDD.
In addition to experiencing a sustained, depressed mood for more than two weeks, patients with SAD tend to develop a lethargic depression as opposed to more irritability — think being glued to the couch rather than lashing out at a loved one. And while MDD is usually associated with loss of appetite and insomnia, people with SAD are more prone to overeating and oversleeping.
The primary differentiating factor with SAD symptoms, however, is that they occur seasonally. “These patients can feel okay much of the year, and their MDD episodes, as opposed to being largely random, have a seasonal pattern — when the days start getting shorter, they start feeling worse,” Brandt says.
How is it caused?
Like major depressive disorder, experts think SAD could be caused by an imbalance of serotonin, a chemical in the brain that contributes to a positive mood. Numerous studies show people with SAD have reduced availability of genes that transport serotonin in the brain. Brandt says that people with SAD may experience imbalances in serotonin as a result of lower levels of light in the winter months.
Since lack of light affects serotonin levels, living in a region where you get less sunlight is one risk factor. Studies show that people who live farther from the equator experience SAD at higher rates — for example, only 1 percent of people in Florida experience SAD, while 9 percent of Alaska residents do.
Having a pre-existing mental illness, especially major depressive disorder or bipolar disorder, is another risk factor. And since there’s scientific evidence of a genetic component involved in SAD, you’re also at a higher risk if a family member has it.
What's the difference between SAD and general depression?
By definition, seasonal affective disorder is a subtype of major depression. The main difference is that while depressive episodes can occur anytime during the year, SAD occurs in seasonal patterns. However, it’s important to note that just because a depressive episode happens in winter doesn’t mean it’s automatically SAD. Some people experience depression in the winter that doesn’t meet the criteria for a seasonal affective disorder diagnosis.
Psychologist Aimee Daramus, who practices in Chicago, says the fall and winter months, especially Thanksgiving to New Year’s, can be an emotionally and physically difficult time for many people for a number of reasons, even if SAD or major depression aren’t actually involved. Some people experience a feeling of just being "over" winter, which many call "winter blues," and this is especially prevalent among those who live in colder climates. But real depression — whether non-seasonal MDD or SAD — is often more severe and debilitating.
Seasonal affective disorder can feel debilitating, but doctors are positive about the number of effective treatment options out there.
“Experiencing the ‘winter blues’ is very different than someone who gets to the point where either they can’t function — they might be missing work or school — or maybe they’re holding it all together but really, deep down, they’re miserable all the time,” says Daramus.
Along with severity, seasonality is the other primary indicator of SAD. General depression in winter is also common, even without a SAD diagnosis. The holidays can be stressful, and in some cases, trigger episodes of major depression. For example, experiencing depressive symptoms around Thanksgiving each year because you have traumatic memories associated with the holiday isn’t necessarily indicative of SAD.
“SAD, by definition, is caused by changes in season, and major depression is not,” says Daramus. “If there’s a specific thing you notice, like ‘something really bad once happened to me in November and that’s why I always get depressed in November,’ by definition, that’s not SAD. It’s a depression caused by an emotional association with the season.” While distinguishing between SAD and major depression can be a bit confusing, it’s important to nail down a diagnosis with your doctor so you can get proper treatment.
How is SAD treated?
Seasonal affective disorder can feel debilitating, but doctors are positive about the number of effective treatment options out there. Like MDD, Brandt says SAD can be effectively treated with a combination of SSRI antidepressants and cognitive behavioral therapy.
But because the chemical imbalance associated with seasonal affective disorder is linked to light, there’s one more treatment: light therapy. Research shows that improvement in mood can be detected after just one session of daily light therapy with a light of 10,000 lux or higher, for as short a time as 20 minutes, and that 40 minutes is not less effective than 60 minutes. In one study, subjects reported an improved mood within 15 minutes of bright light treatment. Brandt says that he’s seen really positive results in his patients with a combination of psychotherapy, light therapy, and SSRI medication, but it’s up to each individual and their physician to come up with their own treatment plan.
If you have symptoms of depression but you’re not sure whether you’re experiencing major depressive disorder or seasonal affective disorder, the most important thing is to talk to a doctor. “Anyone who has depression, whether they feel it’s a seasonal pattern or a single episode, should really get a thorough, expert evaluation of their symptoms,” says Brandt. “As part of that evaluation, I would hope the psych [professional] would take an inventory and try to carefully understand if this is something that happens with rhythm.”
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