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Infections, antibiotics may increase risk for schizophrenia, depression

Infections were associated with increased risk for schizophrenia and affective disorders, particularly those treated with antibiotics and requiring hospitalization, according to recent findings.

“Our primary finding was that the risk of both schizophrenia and depression was increased in those who had infections,” Ole Köhler-Forsberg, MSc, of Aarhus University, Denmark, said in a press release. “Both the non-severe infections that are treated by someone’s own [general practitioner] and the severe infections that require hospitalization. The risk was increased in a dose-response correlation, which means that the risk was higher depending on the number of infections."

To determine associations between infections, exposure to anti-infective agents and risk for schizophrenia and affective disorders, researchers assessed data for all individuals born in Denmark from 1985 to 2000 (n = 1,015,447).

Infections treated with anti-infective agents were associated with increased risk for schizophrenia (HRR = 1.37; 95% CI, 1.2-1.57) and affective disorders (HRR = 1.64; 95% CI, 1.48-1.82). This association exhibited a dose-response and temporal relationship (P < .001).

Increased risk was primarily due to infections treated with antibiotics, as associations with infections treated with antiviral, antimycotic and antiparasitic agents were not significant after mutual adjustment.

Individuals with infections who required hospitalization exhibited the highest risks for schizophrenia (HRR = 2.05; 95% CI, 1.77-2.38) and affective disorders (HRR = 2.59; 95% CI, 2.31-2.89).

“It is also possible that antibiotics in themselves increase the risk of mental disorders due to their effect on the composition of the intestine (microbiota), which has close communication with the brain,” study researcher Michael Eriksen Benros, MD, PhD, of Copenhagen University Hospital, said in the release. “Finally, our findings may be caused by genetic aspects, which is to say that some people have a higher genetic risk for getting more infections as well as a mental disorder.” – by Amanda Oldt

Disclosure: The study was funded by an unrestricted grant from the Lundbeck Foundation.