New findings of a study looking into the complex relationship between antidepressants and the gut microbiome offers fresh insights into how gut bacteria may shape the success of depression treatments.
The research, published recently in Molecular Psychiatry, “Mapping the reciprocal interactions between antidepressants and the gut microbiome: novel targets for the personalisation and optimisation of drug response” was led on by colleagues in our Oxford Health Biomedical Research Centre (OH BRC) Data Science and Preventing Multiple Morbidities Themes.
Depression affects around 300 million people worldwide, and while antidepressants remain a cornerstone of treatment, their effectiveness varies widely. Until now, much of this variability was attributed to genetics.
This study suggests that the gut microbiome, the trillions of bacteria living in our digestive system, plays a crucial role too.
Researchers analysed data from multiple clinical sites in China and the UK, recruiting over 1,000 participants diagnosed with depression. They examined how antidepressant use altered gut bacteria and how these changes influenced treatment outcomes.
The findings found that antidepressants tended to increase anti-inflammatory bacteria such as Bifidobacterium and reduce pro-inflammatory species like Escherichia coli. These shifts may help explain why some people respond better to treatment than others.
The team also identified two groups of bacteria, nicknamed “Microhancers”, which appear to boost antidepressant effects, and “Microlencers”, which appear to dull antidepressant effects.
Understanding these patterns could pave the way for personalised medicine, with clinicians offering the most effective drug depending on a patient’s gut profile.
Paper co-author Dr Amedeo Minichino, OH BRC Researcher and Associate Professor at the University of Oxford’s Department of Psychiatry, highlighted the potential impact, stating:
“This research moves us closer to tailoring antidepressant treatment to each individual. By considering the gut microbiome alongside other clinical and biological markers, we can improve outcomes and reduce side effects. In the future, manipulating gut bacteria before starting medication could become part of routine care.”
The study also explored mechanisms such as biotransformation (where bacteria chemically modify drugs) and bioaccumulation (where bacteria absorb drugs without breaking them down). These processes may significantly influence how much medication reaches the brain.
This discovery opens exciting possibilities for new interventions, including dietary strategies or probiotics to optimise antidepressant response. It marks a major step toward more personalised, effective, and tolerable treatments for depression.
For more information about OH BRC’s work email: ohbrcenquiries@oxfordhealth.nhs.uk
