Toxoplasmosis Infection Has a Possible Causal Relationship With Bipolar Disorder

Bipolar disorder (BD) is related with toxoplasmosis infection, suggesting a potential causal relationship, according to findings published in Journal of Psychiatric Research.

Researchers from the University of Cagliari in Italy conducted a systematic review and meta-analysis to evaluate toxoplasmosis positivity among patients with BD. They searched publication databases through January 2021 and included a total of 23 studies in the analysis.

Studies were conducted in Europe (n=7), the Middle East (n=5), North America (n=5), Asia (n=4), and Africa (n=2), and were published between 2010 and 2020. The studies were of case-control (n=13) or cross-sectional (n=10) designs.

The overall sample size was 4021 for patients with BD and 8669 for healthy controls. The average age was 40.5 years and 49% of study participants were men.

The mean positivity rate for toxoplasmosis was 37% among the study patients, ranging between 3% and 95% compared with 28% (range, 2%-87%) among controls. The studies conducted in Europe (mean, 48%) and the Middle East (mean, 43%) reported higher positivity rates compared with those conducted in Asia (mean, 21%) or the United States (mean, 14%), although the relationship between study region and positivity was not significant (P =.13). However, the variation in positivity rate by region was significantly different among the control cohorts (P =.011).

Toxoplasmosis positivity was related with BD using either fixed effects (odds ratio [OR], 1.34; 95% CI, 1.19-1.52; P <.0001) or random effects (OR, 1.69; 95% CI, 1.21-2.37; P =.0039) models. Significant heterogeneity was observed (I², 84%; P <.0001).

These findings were robust to age, gender, region, sample size, study quality, and study design.

The major limitation of this analysis is the high heterogeneity.Study authors concluded, “This meta-analysis indicates a higher chance of Toxoplasma gondii infection in patients diagnosed with BD than in healthy controls. This indicates the need for accurate assessment of patients with BD for potential parasitosis at their first contact. This is particularly important since toxoplasmosis can have a chronic course and lead to severe consequences, such as encephalitis in immunocompromised individuals, vision loss because of posterior uveitis, and pregnancy loss.”

This article originally appeared on Psychiatry Advisor