Reducing the risk of schizophrenia with an antibiotic?

Doxycycline, an antibiotic frequently prescribed to treat acne and certain infections, may have a protective effect against the development of schizophrenia— a surprising but plausible discovery made by Finnish researchers.Nearly half of psychotic disorders occur in patients who have already consulted a psychiatrist during their adolescence. “Generally, young people who use psychiatric services during adolescence are still far from the onset of psychosis, making this an opportune time for preventive intervention,” said the authors of the study published in the American Journal of Psychiatry. Unfortunately, to date, few prevention methods have been identified.Could taking doxycycline alone have the potential to reduce the risk of psychotic disorders in adulthood? Results from 56,000 patients seem promising in showing that this is the case, at least for schizophrenia.Consultation of Finland's national health registries made it possible to identify all individuals born 1987 to 1997 who had received psychiatric services between the ages of 13 and 18 and who had also been prescribed antibiotics. They were followed up until the age of 30. Nearly 30% of them (n=15,105) received doxycycline, while the others were prescribed another antibiotic.It appeared that patients who had used psychiatric services during childhood and adolescence were less likely to be diagnosed with schizophrenia when treated with doxycycline than those treated with any other antibiotic.At the 10-year followup, the risk of schizophrenia was 1.4% for individuals who had received at least one dose of doxycycline, while it increased to 2.1% when another antibiotic had been prescribed.When isolating patients who had been hospitalized in a psychiatric ward during adolescence, taking doxycycline reduced the risk of schizophrenia over both 10 and 15 years. Patients exposed to a high cumulative dose of doxycycline (≥3000 mg) saw their risk of schizophrenia drop by approximately 30%.Neuroprotective and anti-inflammatory effectsThis antibiotic from the tetracycline family is known for its high brain penetration and has demonstrated certain neuroprotective effects in experimental models, particularly in neurodegenerative diseases and central nervous system trauma.In vitro studies have suggested that doxycycline reduces inflammation in brain cells and modulates synaptic pruning. Since excessive synaptic elimination is thought to be involved in the onset and progression of certain psychotic disorders, including schizophrenia, taking doxycycline may therefore act upstream of synaptic density loss.However, doxycycline was not associated with a lower risk of developing other psychotic disorders. These results may be attributable to particularly high inflammatory activity in individuals with schizophrenia, who may benefit more from the preventive effect of the antibiotic and its anti-inflammatory properties.“Beyond its direct neuroprotective effect, it is possible that doxycycline also has an impact on brain health due to its effectiveness against one or more infectious agents that may play a causal role in the development of psychosis,” noted the researchers, who acknowledge that further research is needed to fully understand the underlying mechanisms.In 2024, a population cohort study showed that the benefits of doxycycline were not only observable in prevention, but also contributed to improving the overall functioning of individuals with schizophrenia.

Reducing the risk of schizophrenia with an antibiotic?

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