Common Antibiotic Doxycycline May Lower Schizophrenia Risk

Research published in the American Journal of Psychiatry indicates that the antibiotic doxycycline may significantly reduce the risk of developing schizophrenia among adolescents. In a study involving over 56,000 young people attending mental health services, those treated with doxycycline showed a 30–35% lower likelihood of developing the severe mental disorder compared to peers treated with other antibiotics.

The collaborative study, conducted by researchers from the University of Edinburgh, the University of Oulu, and University College Dublin, applied advanced statistical modeling to extensive healthcare register data from Finland. Schizophrenia typically emerges in early adulthood and is characterized by symptoms such as hallucinations and delusions.

Researchers explored the potential of repurposing doxycycline, a widely used antibiotic for conditions like infections and acne, as a preventive measure against severe mental illness. They theorized that the antibiotic’s anti-inflammatory properties might play a role in protecting brain development. Previous studies have suggested that doxycycline can reduce inflammation in brain cells and influence synaptic pruning, a natural process that refines neural connections. Excessive pruning has been linked to schizophrenia.

The findings underscore the need for effective interventions for young people at risk of developing schizophrenia. Professor Ian Kelleher, the study’s lead and a Professor of Child and Adolescent Psychiatry at the University of Edinburgh, highlighted the significance of the results: “As many as half of the people who develop schizophrenia had previously attended child and adolescent mental health services for other mental health problems. At present, though, we don’t have any interventions that are known to reduce the risk of going on to develop schizophrenia in these young people. That makes these findings exciting.”

Further analysis revealed that the reduced risk of schizophrenia among those treated with doxycycline was not solely attributable to the treatment of acne, nor was it likely to be explained by other hidden differences between the groups.

While the observational nature of the study means that definitive conclusions about causality cannot be drawn, the results encourage further investigation into the protective effects of doxycycline and other anti-inflammatory treatments in adolescent psychiatry patients. As Professor Kelleher noted, the findings serve as a promising signal for future research aimed at reducing the risk of severe mental illness in adulthood.

This study adds to the ongoing discourse surrounding the potential for existing medications to be repurposed for new therapeutic applications. As researchers continue to explore the intersections of physical health and mental health, doxycycline may represent a significant step forward in understanding how to better support at-risk youth.

For more information, refer to the American Journal of Psychiatry, 2025 edition. DOI: 10.1176/appi.ajp.20240958.