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Seasonal Affective Disorder (SAD) and Vitamin D

Beautiful senior woman and man in sunny winter nature ice skating.

Seasonal Affective Disorder, which coincidentally has the acronym SAD, refers to symptoms of depression that occur seasonally, with the emergence of symptoms during the fall and winter months, and a dissipation of those symptoms once winter transitions into spring. SAD can occur in those who already suffer from depression, but it can also affect those who are not clinically depressed. Symptoms typically include: fatigue, lack of interest in normal activities, social withdrawal, weight gain, and a craving for carbohydrate foods.

SAD is linked the reduction in natural sunlight.

Although there are still a lot of questions as to what causes SAD, one prominent thing that has been linked to SAD is the reduction in natural sunlight that typically occurs during the winter months. This is why geographic areas in the US that are father north typically have a higher rate of people who experience SAD. The farther away from the equator you are, the less sunlight you get each day. As an example, Lansing Michigan gets an average of 36% sunshine during the winter months. In contrast, Tucson Arizona gets an average of 80% sunshine during those same months.

One of the biggest benefits that we get from direct exposure to the sun is Vitamin D.

Although studies have been mixed, there has been some indication that finding a way to increase Vitamin D during the winter months may help alleviate some of the symptoms of SAD. This is why many people have turned toward Light Therapy, which typically utilizes a specialized type of lamp or light box that mimics natural sunlight but filters out most of the harmful UV rays. If you choose to go this route, be sure to follow all instructions very carefully, as this product can cause damage to your eyes if used incorrectly, or if you are taking medication that increases eye sensitivity.

However, artificial light can never fully compensate for natural sunlight, which is 13 times more intense than the artificial light emitted by light boxes! This is why it is recommended, if at all possible (even if it is cold!), to get outside and expose yourself to the natural sunlight on a daily basis for at least 30 minutes. Light Therapy should ideally only be used when there is no direct sunlight available or if it is not physically feasible to be outside for 30 minutes.

Another option, especially if your access to natural sunlight is limited, is to take a Vitamin D supplement.

Although studies have been mixed, some research has suggested that taking a vitamin D supplement can help alleviate symptoms of SAD. Some studies have indicated that as many as 70% of us are Vitamin D deficient, so chances are it is something your body may benefit from, even if you don’t experience symptoms of SAD. As always, if you are thinking of starting up a supplement regimen, be sure to consult with your primary care doctor first to ensure this is an appropriate treatment for your individual needs, and to determine your correct dosage.


  1. Average Winter Sunshine by State
  2. Vitamin D vs broad spectrum phototherapy in the treatment of seasonal affective disorder, by F. Gloth, W. Alam, and B. Hollis (1999). Journal of Nutrition Health and Aging.
  3. Possible contributions of skin pigmentation and vitamin D in a polyfactorial model of seasonal affective disorder, by Alan Stewart, Kathryn Roecklein, Susan Tanner, Michael Kimlin.
Christina Stai

Author: Christina Stai

Dr. Christina Stai is a licensed clinical psychologist in both California and Iowa. She specializes in young children and received her doctorate in Psychology (Psy.D.) from Azusa Pacific University, an APA accredited school near Los Angeles. She completed an APA accredited internship and APPIC accredited postdoctoral fellowship at a residential emergency shelter with abused and neglected foster youth.  We are proud that she has joined Hope Springs.

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