Major depressive disorders increase the susceptibility to self-reported infections in two German cohort studies.

We found increased risks of mild infections in patients with MDD diagnosis and a dose-response relationship between depressive symptom severity and infection frequency. While causal immunological pathways remain unclear, the results of our study might contribute to a change in prevention strategies, e.g. by recommending vaccination against influenza and S. pneumoniae to MDD patients because observed effect sizes in our study are similar to those of patients with cardiovascular and metabolic diseases for which the respective vaccinations are recommended.