Barcelona – October 18, 2026 -- Young adults who received antibiotics from childhood onward had 1.5 times the odds of irritable bowel syndrome (IBS) at age 24 (95% CI 1.0–2.2), according to a study presented at UEG Week 2026.
Study tracks 2,853 Swedish participants from age 9–11
Researchers analysed data from 2,853 participants in the Swedish BAMSE birth cohort. Antibiotic prescriptions came from the Swedish Prescribed Drug Register, covering 2005, when participants were aged 9–11, until one year before IBS was assessed at age 24.
At 24, 10.0% of participants had IBS. Antibiotic exposure was higher among those with IBS, at 87.8%, versus 80.2% among those without. The 1.5-times odds ratio was adjusted for sex and family socioeconomic status.
Odds of IBS climb with each additional prescription band
Compared with participants who received no antibiotics, those with one or two prescriptions had 1.3 times the odds of IBS (95% CI 0.9–2.0). Three to five prescriptions raised the odds to 1.6 times (95% CI 1.0–2.4), and six or more to 1.7 times (95% CI 1.1–2.6).
Cephalosporins carry 6.0-fold odds at three or more prescriptions
Tetracyclines and cephalosporins stayed significantly associated with IBS after adjustment for sex and family socioeconomic status. Any tetracycline use was linked to 1.4 times the odds (95% CI 1.1–1.8). Three or more cephalosporin prescriptions were linked to 6.0 times the odds (95% CI 1.9–18.8), though the wide confidence interval reflects substantial statistical uncertainty.
Gut microbiome is a possible pathway, but the study did not test it
The study did not investigate why antibiotic exposure was associated with IBS. Lead author Dr Jessica Sjölund pointed to the gut microbiome as one possible pathway, noting that earlier studies show antibiotics can alter it and that such alterations are thought to play a role in IBS.
Sjölund said the findings should not discourage antibiotic use when needed, but add to the reasons for avoiding unnecessary prescribing because repeated exposure may carry longer-term effects.