Antibiotic use and the development of depression: A systematic review

Increasingly, disruption of the gastrointestinal ecosystem is thought to be involved in the pathogenesis of several medical conditions, including depression. Antibiotics can induce substantial changes in the gastrointestinal microbiota and several lines of evidence suggest that antibiotics exposure may increase the risk of developing depression. This systematic review examined this potential association.

PubMed, Ovid EMBASE, CINAHL, and PsychINFO databases, as well as unpublished resources, were searched for studies in humans published from 2000 onwards. The studies needed to consider the connection between antibiotic exposure (either alone or in combination with other antibiotics and medications) and the development of depressive symptoms and/or disorders (in isolation to other psychological conditions).

Nine studies met the eligibility criteria. All were observational in nature. The studies were conducted in different age groups with various indications for receiving antibiotics. Together, these relatively low-quality studies suggest a potential association between antibiotic exposure and subsequent development of depression symptoms. Specifically, studies from the United Kingdom and Sweden indicate that the risk of depression is increased by at least 20%, with the former (over 1 million participants) reporting an increased risk with the number of courses and agents used, that persists with a slow decline over the ten years following exposure.

The inherent limitations associated with the studies' methodologies make a reliable conclusion difficult. While the risk of antimicrobial resistance may prohibit large randomised clinical trials in healthy individuals, future placebo-controlled trials with antibiotics-based protocols (e.g. for acne) should explore their effect on mental health.