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.

For more information, check this curated collection of articles on SAD.