Initial T. gondii IgG Antibody Predicts Subsequent New-Onset Schizophrenia among Military Members

Purpose Several studies have documented an association between T. gondii IgG antibodies (Ab) and schizophrenia (SCZ) in serum specimens drawn after diagnosis. We report on a preliminary case-control study evaluating Ab in serum drawn before illness onset among service members medically discharged from the military with a diagnosis (Dx) of SCZ. Methods All cases had a mental health hospitalization (MHH) before medical discharge from the military; MHH date was assumed to mark illness onset. All cases were discharged from the military with SCZ Dx. We evaluated the association between initial Ab and subsequent new-onset SCZ. Two approaches were used to differentiate groups of subjects: those with ≥12 months from initial draw to onset, and those with <12; and those with ≥3 years since last military entry to onset and those with <3. We also evaluated the Dx assigned during their military MHH. Ab was considered ‘positive’ if in the highest 5% and ‘negative’ if in the lowest 80%. Results 180 cases had an initial serum drawn followed by a MHH and subsequent medical discharge from the military with a SCZ Dx. There were 529 controls. The overall odds ratio (OR) for a positive IgG was 1.89 (p=0.077), and did not vary between those with ≥12 and <12 months from initial draw to onset. For those with <3 years since last entry there was no association (OR= 1.02); for those with ≥3 years the OR=3.76 (95% confidence interval 1.31–10.8). There were no differences in MHH Dx categories between those with ≥12 and <12 months from initial draw to onset. Those with ≥3 years since last entry were more likely to have a Dx of affective psychosis than those with < 3 years (22.4% vs. 9.6%, p=0.06). Discussion This preliminary study documents that initial T.gondii IgG obtained before onset of illness predicts later SCZ. This association was strongest for those with ≥3 years of service, and this group had a higher proportion of affective psychoses from first MHH. SCZ associated with T. gondii may reflect a different disease process than other SCZ. This hypothesis will be explored and tested in a much larger case-control study now underway.