A reader asks:

I believe I may have Seasonal Affective Disorder (SAD). I’m often in a good mood in summer. However, my mood gets worse during winter every year, although it improves during sunny days. As a skeptical person, I wonder if this is enough to be diagnosed with SAD. And are there any effective treatments beside light therapy? Could Vitamin D supplements help? Many thanks.

Answer:

You’ve taken a first step by noticing — and acknowledging — that your mood state varies seasonally, and connecting it to what may be SAD.  But that realization does not equate with a diagnosis, which requires an examination of the pattern and severity of mood, and a host of associated symptoms.  So take the next step: Go to our website section on self-assessments and complete the confidential seasonality (AutoPIDS) and depression (AutoSIGH) evaluations. The feedback will tell you whether SAD is a likely diagnosis, and will also tell you whether you should take a third step: seeking professional attention to determine whether to begin self-treatment with light therapy.  As for Vitamin D, there is no convincing evidence that it counteracts depressed mood in winter.