Am J Psychiatry

Common antibiotic may cut schizophrenia risk in high-risk adolescents

November 7, 2025

Study details: This emulated target trial analyzed Finnish national health registry data from 56,395 adolescents (ages 13 to 18) who'd attended psychiatric services and received antibiotics. Of these, 28.7% were treated with doxycycline. Researchers used the g-formula to estimate schizophrenia risk across cumulative doxycycline exposure levels, adjusting for confounders such as age, sex, and psychiatric diagnosis.

Results: At 10-year follow-up, schizophrenia incidence was 2.1% among those treated with non-doxycycline antibiotics. In contrast, risk was significantly lower in doxycycline-treated groups: 1.4% in low and medium cumulative dose groups (risk ratio [RR], 0.65–0.70) and 1.5% in the high-dose group (RR, 0.70). These findings were consistent across inpatient and outpatient psychiatric samples.

Clinical impact: Doxycycline may offer neuroprotective benefits in adolescents at elevated risk for schizophrenia. While causality cannot be confirmed due to the observational design, the findings support further investigation into repurposing doxycycline as a preventive intervention in adolescent psychiatry.

Source:

Lång U, et al. (2025, November 5). Am J Psychiatry. Doxycycline Use in Adolescent Psychiatric Patients and Risk of Schizophrenia: An Emulated Target Trial. https://pubmed.ncbi.nlm.nih.gov/41190738/