Depression correlated with cellular immunity in systemic immunodeficient Epstein-Barr virus syndrome (SIDES).

We conducted studies on the peripheral blood of 12 depressed patients with previous diagnoses of mood and/or personality disorders. These patients, and other depressives we observed informally, were resistant to infectious mononucleosis during an epidemic of that illness. All 12 had serologic evidence of a chronic or recrudescent viremia caused by the Epstein-Barr virus (EBV), the infectious agent in infectious mononucleosis. Additional evidence that EBV viremia may be causally related to depression was provided by a strong correlation between the intensity of depressive symptoms and the cellular immune response to the EBV infection.