Seasonal Affective Disorder (SAD), and its milder cousin, the “winter blues,” are real. However, the scientific consensus about the core features, and causes, of this problem are not as fixed as they once were.
SAD is a variation of major depression that occurs in late fall and winter. In addition to the classic symptoms of major depression, such as a depressed mood, people with SAD often:
- sleep much more than usual, with difficulty awakening
- feel sluggish
- eat more than usual, crave carbohydrates, and experience significant weight gain that reverses in spring.
For people with this cluster of symptoms, light therapy is an ideal treatment. The reason? Light therapy impacts what many researchers and clinicians believe is the underlying cause of the problem, namely a disturbance of circadian rhythms.
Circadian rhythms govern our sleep/wake cycle, and with longer nights and later sunrise in winter, the body clock shifts later, affecting our sleep and other behaviors linked to the circadian system.
Some scientists have questioned whether SAD diagnosis persists across the lifespan. They found only depression, and carbohydrate craving, predicted long-term, repeated winter episodes. In other words, only those two symptoms were correlated with having SAD in future years. They thus concluded that SAD is, “a temporary expression of a mood disorder rather than a specific disorder.”
Another group followed individuals for more than 20 years, and found about 3% of cases with repeated episodes of winter depression, interspersed with other years showing no seasonal change. Interestingly, about 3% of the U.S. population – around 10 million people – is estimated to experience a winter episode in any current year.
Depression severity can vary widely from year to year depending on both external conditions (such as weather and location change) and personal factors (such as stress level due to work pressure and family interactions), with a general reduction of seasonal variation in old age. One can learn to sense the risk of a winter mood shift, and take precautionary measures if the symptoms begin to appear.
Causes of SAD
Risk factors for SAD include:
- sunrises of 7:30 AM or later
- mountains or tall buildings that restrict your access to sun
- genetic predispositions for depression, or sensitivity to seasonal change, or both.
Research on these risk factors supports the existence of the SAD, as distinct from unpredictable depressions. For example, the prevalence of SAD increases with northern latitudes in the northern hemisphere, to a point when the prevalence levels off. Further, the sun rises at roughly 6:00 AM throughout the year at the equator, and regions close to the equator show minimal emergence of SAD.
Treatment for SAD
Light therapy is the most widely accepted treatment for SAD, and is listed as an option in the American Psychiatric Association guidelines. For information on light boxes, from the research behind them to how people use them for SAD, see Light Therapy for Beginners: Six Steps.
Cognitive therapy specifically developed for SAD can be helpful, and even reduce the chance of a depressive shift the following year. Antidepressants can be helpful, but may take many weeks before they act. A promising novel treatment uses an electronic device that ionizes the air.
What Should You Know About SAD?
For more information, visit cet.org, the site of the Center for Environmental Therapeutics. This nonprofit is the go-to site for information about mood, sleep, and circadian rhythms. For feedback about your current level of depression, and the degree to which it is seasonal, take the Center’s free, confidential self-assessment. If you are seeking treatment, you can print out the feedback to share with your doctor.