Are SSRIs Bad for the Immune System?

The findings of a study published in January 2006 suggest that antidepressants may affect the immune system. This study was conducted by scientists from Georgetown University Medical Center in Washington, D.C., and the Robarts Research Institute in Ontario, Canada and was lead by Gerard Ahern, Ph.D., assistant professor of pharmacology at Georgetown. This surprising finding was first revealed in October 2006, when the research team published their findings in Blood. Later, in December, the discovery was picked up by the journal Nature Reviews Immunology.

The team specifically discovered that serotonin is passed between cells in the immune system, where the chemical is used to activate an immune response. In particular, they showed that serotonin is passed between two types of immune cells: dendrite cells and T cells. Selective serotonin reuptake inhibitors (SSRIs), such as Prozac and Zoloft, have been long know to influence the uptake (i.e. the absorption) of serotonin into neurons, but these new findings suggest that this class of drugs may also influence the uptake of serotonin in immune cells.

The role that SSRIs could play in helping or harming the immune system is unclear, however. In theory, SSRIs could restore the immune systems of people who are depressed and prone to infection, or they could bolster immunity and activate autoimmune disease, a condition where the immune system actually attacks the body.

In the end, the team advises patients taking SSRIs to continue their medication regimen. The researchers hope to develop future studies that will reveal any positive or negative effects in several animal models.