Combined Toxoplasma gondii seropositivity and high blood kynurenine – Linked with nonfatal suicidal self-directed violence in patients with schizophrenia

• Published in: Journal of psychiatric research 2016-01, Vol.72, p.74-81
• Main Authors: Okusaga, Olaoluwa, Duncan, Erica, Langenberg, Patricia, Brundin, Lena, Fuchs, Dietmar, Groer, Maureen W, Giegling, Ina, Stearns-Yoder, Kelly A, Hartmann, Annette M, Konte, Bettina, Friedl, Marion, Brenner, Lisa A, Lowry, Christopher A, Rujescu, Dan, Postolache, Teodor T
• Format: Article
• Language: English
• Subjects: Adult; Female; Humans; Kynurenine; Kynurenine - blood; Male; Non-fatal suicidal self-directed violence; Odds Ratio; Psychiatry; Schizophrenia; Schizophrenia - blood; Schizophrenia - complications; Schizophrenia - epidemiology; Self-Injurious Behavior - blood; Self-Injurious Behavior - complications; Self-Injurious Behavior - epidemiology; Suicide, Attempted - statistics & numerical data; Toxoplasma gondii; Toxoplasmosis - blood; Toxoplasmosis - complications; Toxoplasmosis - epidemiology
• ISSN: 0022-3956; 1879-1379
• DOI: 10.1016/j.jpsychires.2015.10.002

Abstract Toxoplasma gondii (T. gondii ) chronic infection and elevated kynurenine (KYN) levels have been individually associated with non-fatal suicidal self-directed violence (NF-SSDV). We aimed to test the hypothesis that the association between T. gondii seropositivity and history of NF-SSDV would be stronger in schizophrenia patients with high plasma KYN levels than in those with lower KYN levels. We measured anti- T. gondii IgG antibodies and plasma KYN in 950 patients with schizophrenia, and used logistic regression to evaluate the relationship between NF-SSDV and KYN in patients who were either seropositive or seronegative for T. gondii . For those with KYN levels in the upper 25th percentile, the unadjusted odds ratio for the association between NF-SSDV history and KYN in T. gondii seropositive patients was 1.63 (95% CI 1.01 to 2.66), p  = 0.048; the adjusted odds ratio was 1.95 (95% CI 1.15 to 3.30), p  = 0.014. Plasma KYN was not associated with a history of NF-SSDV in T. gondii seronegative patients. The results suggest that T. gondii and KYN may have a nonlinear cumulative effect on the risk of NF-SSDV among those with schizophrenia. If confirmed by future longitudinal studies, this result is expected to have both theoretical and clinical implications for the prevention and treatment of suicidal behavior.