What is seasonal affective disorder?
Seasonal affective disorder is a strong tendency to become depressed during a specific time of the year — most often in late fall, continuing into winter. There can be other years when the dip is milder than a full depression, or even absent. Summers are most often symptom-free.
What causes it?
Winter SAD is linked to less daylight, which is exacerbated by spending more time indoors. The sensitivity to these changes varies by individual. Some people react to the first signs of seasonal change around the fall equinox in September, while others’ moods don’t plunge until December. The most common period for the onset of a SAD episode is late October through November. January and February are the worst months overall, and the symptoms don’t fully subside until early May. Given the continued time spent indoors through the ongoing pandemic, symptoms experienced during winter may not abate with the arrival of spring next year.
Confinement indoors for long periods, under typical room light levels, essentially creates a mimic of eternal winter, overriding the seasonal transition to longer days and the natural bright light exposure that would otherwise break the winter cycle with a spontaneous return to normal mood, energy, appetite, and sleep. We have seen this before in people with chronic, nonseasonal depression, who limit their activities, linger in bed, stop working, and don’t get out.
How many people are affected by SAD?
Seasonal affective disorder is estimated to affect 10 million Americans, or 3% of the population. An additional 10% may have mild cases. The disorder affects women four times more than men, and usually begins between the ages of 18 and 30, though children can suffer too. Some people’s symptoms are severe enough to affect quality of life; 6% require hospitalization. Those diagnosed with SAD experience major depression seasonally for at least two consecutive years. But there are significant geographic differences, especially in latitude, since winter nights are hours longer in the north than in the south.
Who is most at risk for developing SAD?
Most studies have zeroed in on women of childbearing age, but SAD is definitely not age- or sex-specific. Lower estimates for men may be biased by some men’s reluctance to admit to mood shifts. In a study I conducted many years ago, published in the Journal of Biological Rhythms, a random sample of New Yorkers rated key symptoms of seasonal change — for example, weight gain, longer sleep, and reduced motivation, productivity, and social interest. The survey specifically avoided calling attention to the psychiatric connection. There was no difference in SAD-like symptoms between men and women.
What are the symptoms?
Physical symptoms that precede the mood shift include difficulty waking up on schedule, daytime fatigue, a craving for carbohydrates, and weight gain. Once the depression hits, the symptoms mimic those of nonseasonal depression, including loss of motivation for work or other activities, reduced social contact, and anxiety. The difference is that the onset of the SAD episode is predictable, usually weeks after the physical symptoms appear, and countermeasures can begin before the mood swing is severe. In that sense, SAD patients are luckier than their cohorts with nonseasonal depression.
At what point is it necessary to see a doctor?
Most people with SAD have experienced the winter shift for years before identifying the seasonal pattern. And because they can firmly anticipate feeling better after several months, they may brush it off as a temporary burden, even though they can become quite dysfunctional. Others have sought treatment with antidepressants, often unnecessarily maintained year-round, because neither they nor their doctors have put a finger on the seasonal timing.
If symptoms are severe, that should prompt consultation with a primary care physician, a psychiatrist, or other mental health professional. The challenge for patients is recognizing when they should seek help, and if they do, making sure their provider has the expertise to supervise SAD-specific treatment. Responsibility lies both with the patient and doctor. I urge patients to document their symptoms with a set of free online self-assessment questionnaires from the nonprofit Center for Environmental Therapeutics. The printout of results provides a solid basis for guiding a consultation with a healthcare provider.