Caffeine containing drinks can contribute in huge ways to seasonal affective disorder

Seasonal affective disorder is due to dysregulation of calcium homeostases. See this post.

Caffeine activates ryanodine receptors resulting in release of intracellular calcium from sarcoplasmic reticulum and endoplasmic reticulum.

Drinking coffee, tea and/or other caffeine containing drinks can upset calcium homeostases resulting in seasonal affective disorder. Herbal teas are not safe alternatives due to high levels of antioxidants in herbal teas. In the United States tap water is the only safe drink.