Medications used many years earlier can still influence the human gut microbiome, according to a large-scale study conducted by the University of Tartu Institute of Genomics. Surprisingly, benzodiazepines, which are commonly prescribed to treat anxiety, were found to influence the gut microbiome to a degree similar to broad-spectrum antibiotics. Confirmed long-term microbial shiftsFollow-up samples from a subset of participants confirmed that starting or stopping certain drugs caused predictable microbial shifts, suggesting causal effects. “This is a comprehensive systematic evaluation of long-term medication effects on the microbiome using real-world medical health records,” said Professor Elin Org, corresponding author. DOI: 10.1128/msystems.00541-25This work was funded by the Estonian Research Council grant PRG1414 (to E.O.