People who frequently use antibiotics are more likely than those who don’t to develop colorectal cancer, a study suggests.

Overall, people who had total antibiotic usage of six months or more were more likely to develop colorectal cancer (odds ratio 1.17) than those who had no antibiotic use, the study team reported in the Journal of the National Cancer Institute.

However, when researchers excluded any antibiotic usage within two years of a cancer diagnosis, the association was no longer statistically significant.

The authors examined data from Swedish national registers for 40,545 individuals diagnosed with colorectal cancers from 2005 to 2016, as well as 202,720 matched controls.