ASK THE EXPERT : Linda Carpenter , MD
Your health questions answered by physicians
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How is seasonal affective disorder different from wintertime gloom ?
Seasonal affective disorder ( SAD ) is defined as a pattern of recurring depressions whose onset and offset are related to the seasons , typically starting in winter and resolving in spring . Sometimes , the depression can start in winter and become chronic . There ’ s also a spectrum of severity ; a lot of people have mild versions . Anywhere from 1 to 10 percent of people develop SAD , and it ’ s far more common in women than in men .
The onset of SAD tends to correspond with shortening light , not cold . The hypothesis is that light receptors in the eyes , which send signals to the brain , are effecting brain changes that cause depression . We think there are several chemical systems involved , like melatonin , serotonin , and other neurotransmitters . There ’ s no clear biomarker to show who ’ s vulnerable . We only know that people who are prone to mood fluctuations are more prone to SAD .
Depression is often characterized by changes in energy and appetite . With SAD , those changes have a “ hibernating bear ” quality — carbohydrate craving , overeating , decreased energy , more sleeping . Many people with SAD also get seasonal anxiety . The primary treatments are bright light , psychotherapy , antidepressants , and vitamin supplements — in particular , vitamin D . If you have even mild seasonal depression , it ’ s reasonable to get checked for a vitamin D deficiency . Bright light therapy is another pretty benign place to start . There are a variety of light devices out there — masks , wands , dawn simulators — but a bright light must be 10,000 lux to be effective . Some of my patients find it annoying to sit and stare at a light . But I tell them just having the light in the room is helpful , because photons still make their way into your eyes . Just don ’ t use it toward the end of the day , because it can keep you awake , and if you have an eye disease or take medications that make you photosensitive , you probably shouldn ’ t use it .
Remember that if SAD causes problems in daily life , there are treatments . And if your depression doesn ’ t resolve in the spring , that ’ s a sign you may want to get treatment : The more chronic a depression becomes , the harder it is to treat .
Linda Carpenter , MD , is a professor of psychiatry and human behavior at Brown and chief of the Mood Disorders Program at Butler Hospital . Her research includes studying the effect of light on the brains of people with SAD and depression . HD @ B
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