Taking antibiotics from late childhood into early adulthood may raise the likelihood of irritable bowel syndrome (IBS) by age 24, and the risk appears to grow with each additional course. These are the main findings of a new study presented at UEG Week 2026 in Barcelona.

The researchers analysed records from 2,853 people taking part in the Swedish BAMSE birth cohort. Their antibiotic prescriptions came from the Swedish Prescribed Drug Register, covering the period from 2005, when participants were 9 to 11 years old, until one year before IBS was assessed at age 24.

Key findings

By age 24, 10.0% of participants had IBS. Antibiotic use was more common among those with the condition: 87.8% had been prescribed antibiotics, compared with 80.2% of those without IBS. After adjusting for sex and family socioeconomic status, people who had received antibiotics had 1.5 times the odds of IBS compared with those who had not (95% CI 1.0–2.2).

The association also strengthened with the number of prescriptions. 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). Those with three to five prescriptions had 1.6 times the odds (95% CI 1.0–2.4), and those with six or more had 1.7 times the odds (95% CI 1.1–2.6).

Specific antibiotic classes

When the researchers looked at individual drug classes, two remained significantly linked to IBS after adjusting for sex and family socioeconomic status:

• Any use of tetracyclines was associated with 1.4 times the odds of IBS (95% CI 1.1–1.8).
• Three or more prescriptions for cephalosporins were associated with 6.0 times the odds (95% CI 1.9–18.8).

A possible explanation

The study did not investigate the reasons behind the link. However, the authors point to the gut microbiome as a plausible pathway. Earlier research has shown that antibiotics can disrupt gut bacteria, and changes to the microbiome are thought to play a role in IBS, so this disruption could be one way the association arises.

Lead author Dr Jessica Sjölund stressed that the findings should not discourage necessary antibiotic treatment, since these medicines remain vital for bacterial infections. Instead, the results point to possible long-term effects of repeated exposure and reinforce the importance of avoiding unnecessary prescriptions.