Dear Dr. Cannell:
In 2003, my husband and I moved to the Olympic Peninsula in western Washington State, an area famous for cloudy, wet winters. I have always suffered from seasonal affective disorder (SAD), but it became worse once we moved.
In 2007, I began taking vitamin D (1400 I.U. per day from October to May) due to research that showed that vitamin D may reduce the risk of breast cancer. To my surprise, I did not get SAD that winter. I now take vitamin D as an antidepressant as soon as the days get shorter. I increase the amount whenever I start to feel a touch of depression. By February, I am taking 6,000 I.U. per day. Loving those rainy days!
Last year, four researchers from various institutions supported your personal experience in one of my favorite journals, Medical Hypotheses. (Without Medical Hypotheses, I would never have had my vitamin D and autism theory published in 2007).
Stewart AE, Roecklein KA, Tanner S, Kimlin MG. Possible contributions of skin pigmentation and vitamin D in a polyfactorial model of seasonal affective disorder. Med Hypotheses. 2014 Nov;83(5):517-25.
As these researchers make clear, SAD is complex, with many factors contributing to it. Although not everyone with SAD is helped by vitamin D, some are. I recommend that anyone who is affected by SAD, to try supplementing with vitamin D. However, I would suggest supplementing with 10,000 IU/day in the fall and winter and full body sunbathing in the spring and summer.
There are 3 randomized controlled trials of vitamin D in treating SAD; two trials show no treatment effect and one does, but the doses were no where near 10,000 IU every day. Not all patients were vitamin D deficient at the start of the studies. Also, pre and post treatment vitamin D blood levels were not obtained to assure compliance and adequate doses.
I am happy to hear that vitamin D supplementation has helped
John Cannell, MD