Preexisting Autoimmune Disease and Severe Infection Increase Schizophrenia Risk

Autoimmune and inflammatory factors are among the numerous putative contributors to the risk for schizophrenia. One hypothesis posits that inflammation of the central nervous system decreases function of the blood–brain barrier, thereby enabling autoantibodies generated from autoimmune disease to breach the barrier, react with brain tissue, and produce psychiatric symptoms. To test this, investigators examined data from two Danish national health registries (1977–2006) on 3,567,573 people.

Among 39,076 people diagnosed with schizophrenia, 9221 had prior hospital contact for at least one infection, 927 had preexisting autoimmune disease (HIV was excluded), and 444 had both. Overall, the incidence rate ratio (IRR) of schizophrenia increased si…