Toxoplasma gondii and Other Risk Factors for Schizophrenia: An Update

Abstract

The failure to find genes of major effect in schizophrenia has refocused attention on nongenetic, including infectious factors. In a previous study, antibodies to Toxoplasma gondii were found to be elevated in 23 studies of schizophrenia (OR 2.73; 95% CI 2.10–3.60). The current study replicates this finding with 15 additional studies (OR 2.71; 95% CI 1.93–3.80) and compares this with other identified schizophrenia risk factors. The highest risk factors are having an affected mother (relative risks [RR] 9.31; 95% CI 7.24–11.96), father (RR 7.20; 95% CI 5.10–10.16), or sibling (RR 6.99; 95% CI 5.38–9.08) or being the offspring of immigrants from selected countries (RR 4.5; 95% CI 1.5–13.1). Intermediate risk factors, in addition to infection with T. gondii, include being an immigrant from and to selected countries (RR 2.7; 95% CI 2.3–3.2), being born in (RR 2.24; 95% CI 1.92–2.61) or raised in (RR 2.75; 95% CI 2.31–3.28) an urban area, cannabis use (OR 2.10–2.93; 95% CI 1.08–6.13), having minor physical anomalies (OR 2.23; 95% CI 1.42–3.58), or having a father 55 or older (OR 2.21–5.92; 95% CI 1.46-17.02). Low-risk factors include a history of traumatic brain injury (OR 1.65; 95% CI 1.17–2.32), sex abuse in childhood (OR 1.46; 95% CI 0.84–2.52), obstetrical complications (OR 1.29–1.38; 95% CI 1.00–1.84), having a father 45 or older (OR 1.21–1.66; 95% CI 1.09–2.01), specific genetic polymorphisms (OR 1.09–1.24; 95% CI 1.06–1.45), birth seasonality (OR 1.07–1.95; 95% CI 1.05–2.91), maternal exposure to influenza (RR 1.05; 95% CI 0.98–1.12), or prenatal stress (RR 0.98–1.00; 95% CI 0.85–1.16).

schizophrenia, Toxoplasma gondii, risk factors