Background and Aim: Seasonal patterns of food intake are found in healthy individuals and particularly in patients with seasonal affective disorder (SAD). One nutritional choice is a vegetarian diet. Methods: In a Finnish population study, FINRISK 2012, information about diet and SAD was collected. In a Dutch outpatient clinic, SAD patients were asked if they were vegetarian. Results: The percentage of SAD patients among Finnish vegetarians was 4 times higher than in the normal population. The percentage of vegetarians among the SAD patients in a Dutch outpatient clinic was 3 times higher than in the normal population. In the Dutch population, the seasonal loss of energy, in particular, is related to vegetarianism. Conclusion: These findings suggest a possible link between vegetarianism and SAD.