Depression is the most common mental health disorder. It has consequences not only on individuals but also on social and political levels. We argue that depressive symptoms impair political participation by reducing the motivation and physical energy of sufferers. We test our hypotheses by conducting regression analyses of four nationally representative cross-sectional and longitudinal surveys that collectively span many democracies. Our results are threefold. First, we find that the severest depressive symptoms lower the probability of voting by 0.05–0.25 points, an effect that is exceeded only by education and age. Second, we show that depressive symptoms negatively affect political interest and internal efficacy, thereby confirming that they diminish political motivation. Third, we find that depressive symptoms most strongly affect physically demanding acts, thereby confirming that they reduce the physical energy required for participation. We conclude by urging scholars to take depressive symptoms seriously in the study of political behavior.