Colorectal cancer is now the leading cause of cancer death among people under 50, according to a recent JAMA study. Researchers once projected this shift would occur around 2030. Instead, it’s happening sooner than expected. As March marks Colorectal Cancer Awareness Month, the disease has also been in the news following the recent deaths of actors Catherine O'Hara and James Van Der Beek, with colorectal cancer cited as the cause of death in Van Der Beek’s case.

For Resa M. Jones, the news is concerning but not surprising.

“I know the data,” Jones said. “Nothing about that really stands out to me because we knew this was where things were heading.”

What did catch researchers’ attention, she said, was how quickly the shift arrived

“The fact that we’ve gotten to this point faster than expected,” Jones said, “that is surprising.”

Several factors may be contributing to the rise among younger adults. Obesity has increased, physical activity has declined and sedentary behavior has become more common. Researchers are also seeing what Jones describes as a generational effect.

“Someone born in 1990 has a substantially higher risk than someone born in 1950, and those born in 2000 have an even higher risk,” she noted.

Jones said researchers are still trying to understand what might be driving that shift.

“Something like that increase is happening,” she said. “What could be explaining the generational effect more so is environmental exposures.”

She noted that emerging research is examining factors such as ultra-processed foods, changes in the gut microbiome, environmental exposures, and microplastics, though the data are still evolving.

At the same time, colorectal cancer rates have actually declined among older adults.

“The increase really is among younger age groups,” Jones said. “There’s actually a decline in cancer among older age groups.”

She said screening has likely played a role in that trend. National guidelines now recommend screening for average-risk adults beginning at age 45. Yet only about 70 percent of eligible Americans have been screened.

“If about 30 percent of the population isn’t being screened, that’s a third of people who don’t have the ability for early detection and prevention,” Jones said.

The timing matters. About half of colorectal cancer diagnoses before age 50 occur between ages 45 and 49.

“If you’re age eligible,” Jones said, “please get screened.”