The prevalence of bipolar disorder in autoimmune disease: a systematic review and meta-analysis.

BACKGROUND At the end of the last century, genome-wide association studies revealed a significant genetic association between bipolar disorder and autoimmune diseases. Subsequently, the theory of immune pathogenesis of bipolar disorder gradually formed, and the research on autoimmune diseases and bipolar comorbidities began to extend to other diseases, but their correlation is still controversial. To explore the differences in the prevalence of bipolar disorder in patients with autoimmune disease and normal healthy people through meta-analysis, and to examine the relationship between bipolar disorder and autoimmune disease by reviewing the relevant literature. METHODS The Cochrane, PubMed, and Embase databases were searched by computer from the date of inception of the database to July 2020. The main topics of the search were based on common autoimmune diseases, including systemic lupus erythematosus, rheumatoid arthritis, psoriasis, multiple sclerosis, ulcerative colitis, Crohn's disease, ankylosing spondylitis, pemphigus, and Sjogren's syndrome. The databases were comprehensively searched for controlled studies regarding the prevalence of bipolar disorder in patients with autoimmune diseases. Review Manager 5.3 software was used for meta-analysis. RESULTS In total, 10 cohort and case control studies were included. From these, 16 control groups were extracted based on nine autoimmune diseases. The meta-analysis demonstrated that the incidence of bipolar disorder was significantly increased in patients with autoimmune disease compared to patients without autoimmune disease, [mean difference (MD) =1.54, 95% confidence interval (CI): 1.28-1.86, P<0.00001]. Also, in the meta-analysis based on five cross-sectional analyses (in which a total of five control groups were extracted based on five autoimmune diseases), the high comorbidity rate of autoimmune diseases and bipolar disorder was verified (MD =2.23, 95% CI: 1.62-3.07, P<0.00001). CONCLUSIONS The prevalence of bipolar disorder is markedly higher in patients with autoimmune disease. Yet, more basic research is needed to verify the special significance of immune mechanisms in bipolar disorder.