Gastrointestinal cancers, which include colorectal, stomach and pancreatic cancer, are rising dramatically in younger adults, though doctors aren’t fully sure why. Even some of the possible causes require more research, they say.

According to a review published Thursday in JAMA, gastrointestinal cancers have become the fastest-growing type of cancers diagnosed in adults younger than 50 in the U.S.

The review, one of the most comprehensive looks at gastrointestinal cancer trends, summarized the findings of major international and U.S. cancer databases, plus 115 papers on gastrointestinal cancers published from January 2014 to March 2025.