Autoimmune diseases and infections as risk factors for schizophrenia.

Immunological hypotheses have become increasingly prominent when studying the etiology of schizophrenia. Autoimmune diseases, and especially the number of infections requiring hospitalization, have been identified as significant risk factors for schizophrenia in a dose-response relationship, which seem compatible with an immunological hypothesis for subgroups of patients with schizophrenia. Inflammation and infections may affect the brain through many different pathways that are not necessarily mutually exclusive and can possibly increase the risk of schizophrenia in vulnerable individuals. However, the findings could also be an epiphenomenon and not causal, due to, for instance, common genetic vulnerability, which could be supported by the observations of an increased prevalence of autoimmune diseases and infections in parents of patients with schizophrenia. Nevertheless, autoimmune diseases and infections should be considered in the treatment of individuals with schizophrenia symptoms, and further research is needed of the immune system's possible contributing pathogenic factors in the etiology of schizophrenia.