Immunoglobulin subclass profiles in depression: Insights from a general population study

The immune system plays a crucial role in defending the body against harmful invaders, with immunoglobulins being key players in pathogen recognition and neutralization. Immunoglobulin dysregulation is linked to various diseases, including autoimmune disorders, immunodeficiencies, and allergies. Previous studies suggest that depression can alter immune function by modifying immunoglobulin production, which may contribute to increased vulnerability to infections and autoimmune diseases. In this study, we examined the association between the immunoglobulin (Ig) subclasses IgA, IgG, IgM, and IgE and different types of depression, alongside epidemiological and environmental factors, using two independent samples from the population-based SHIP (Study of Health in Pomerania) project (TREND-0 N = 3750, START-2 N = 1958). Multiple linear regression analyses revealed that the environmental factors showed distinct associations with immunoglobulin levels. In TREND-0, lifetime depressive disorder was associated with decreased total IgA (p = 0.019) and increased total IgM (p = 0.026), indicating a shift toward impaired local immunity and heightened global immunity. Current depressive symptoms correlated with reduced IgG (p = 0.039) levels, reflecting impaired long-term immunity and immunological memory. These associations were specifically observed in depression, with no significant effects from broader psychiatric conditions. Results on current depression were replicated in START-2, a measurement of lifetime depression was not available here. Additionally, a history of childhood trauma was linked to elevated total IgE (p = 0.028), suggesting an increased susceptibility to allergic responses. These findings highlight the complex relationship between depression and immune function, emphasizing the need for further exploration of these associations in immune-related pathologies.