The findings of a recent study revealed that while there is an association between family history of autoimmune disorders and increased risk for schizophrenia, there is not an association for increased risk of bipolar disorder.
According to William Eaton of Baltimore-based Johns Hopkins University and a team of researchers, previous clinic-based studies of immune function, as well as comorbidity of autoimmune diseases, bipolar disorder, and schizophrenia, suggested a possible link. Studies of non-affective psychosis and schizophrenia also suggested common etiologies.
The team set out to determine the degree to which 30 different autoimmune diseases are risk factors for bipolar disorder, schizophrenia, and non-affective psychosis.
“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,” explained Eaton and team, adding that the risk associated with bipolar disorder remained unknown.
A sample of 20,317 patients with schizophrenia, 39,076 with non-affective psychosis and 9,920 with bipolar disorder was drawn from the Danish Psychiatric Central Register for the study.
To draw a correlation between the three psychiatric disorders and 30 identified autoimmune diseases, data on the sample patients, their parents and siblings was pulled from the Danish National Hospital Register. The register is a compilation of information on all discharges from Danish hospitals since 1977.
The results correlated the findings of previous studies suggesting an association between schizophrenia and autoimmune disease. Specifically, dermatopolymyositis, autoimmune hepatitis, iridocyclitis and Sjogren’s syndrome were identified as precursors to increased risk for schizophrenia when compared to patients whose family histories did not have the autoimmune link.
Researchers said that these relationships also existed for the broader category of non-affective psychosis.
No notable links were found between family history of autoimmune disease and an increased risk for bipolar disorder with the exception of pernicious anemia. Findings revealed an increased risk of 1.7 when compared to patients without a history of pernicious anemia, which suggests a small role for family linkage, researchers said.
On the individual level aside from family history, a history of Guillain-Barré syndrome, Crohn’s disease, and autoimmune hepatitis was associated with an increased risk of bipolar disorder.
Autoimmune diseases develop when the immune system becomes overactive and attacks cells and tissues that are normally present in the body. The immune system becomes confused and identifies normal parts of the body as pathogens.
An autoimmune attack may involve certain organs or tissue in different locations. Treatment usually requires immunosuppression medication to decrease the response.
Eaton and team conclude that “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 team also added that the contrast between bipolar and schizophrenia in the study strengthens the credibility of previous findings related to schizophrenia and also reinforces the distinction between the two disorders.
The study was published recently in the journal Bipolar Disorders.
Source: Bipolar Disorders