Autoimmune Disease, Schizophrenia, and Bipolar Disorder

What do these three things have in common? Nothing… as a whole; although recent study results published in Bipolar Disorders confirm an association between family history of autoimmune disorders and increased schizophrenia risk, the study shows that the former is not associated with increased bipolar disorder risk.

"In our earlier work we showed that thyrotoxicosis, celiac disease, autoimmune hemolytic anemia, and Sjogren's syndrome were more common in the family members of persons diagnosed with schizophrenia… and were more common in the cases of schizophrenia themselves," wrote William Eaton, Johns Hopkins University, Baltimore, MD, and team.

Because the team did not know if an association existed between autoimmune disorders and increased risk for bipolar disorder, they identified 20,317 patients with schizophrenia, 39,076 with non-affective psychosis, and 9920 with bipolar disorder from the Danish Psychiatric Central Register and obtained data on the prevalence of 30 autoimmune diseases in the patients and their nuclear families from the Danish National Hospital Register.

Although they confirmed results from previous studies by finding that family history of dermatopolymyositis, autoimmune hepatitis, Sjogren's syndrome, and iridocyclitis were associated with increased schizophrenia risk compare to not having family history or these disorders, and that family history of various autoimmune diseases was associated with increased non-affective psychosis risk, no significant link was found between such family history and increased bipolar disorder risk, with one exception: pernicious anemia was associated with a 1.7 times greater risk compared with not having a family history of pernicious anemia.

Among the individuals themselves, history of Guillain-Barré syndrome, Crohn's disease, or autoimmune hepatitis was associated with increased bipolar disorder risk.

The authors concluded, “These results continue to suggest a general relationship between autoimmune diseases and schizophrenia. The contrast with bipolar disorder is striking in that, with the exception of a RR of 1.7 for pernicious anemia, there are no significant familial associations at all with autoimmune diseases… The contrast with schizophrenia strengthens the credibility of the findings for schizophrenia, as well as reinforcing the nosologic distinction between the two disorders.”