More Young Adults Are Getting Colon Cancer. Doctors Say Don’t Ignore These Signs

Colorectal cancer is no longer a disease that mostly strikes people in their 60s and 70s. It has quietly become the leading cause of cancer deaths in Americans under 50, and doctors still cannot fully explain why cases in young adults keep climbing.

“We are seeing a clear uptick in colorectal cancer in younger generations,” Haddon Pantel, MD, a colorectal surgeon at Yale Medicine, told Yale Medicine. The shift has forced a rewrite of screening guidelines and left researchers scrambling to identify the culprit.

How much colorectal cancer is rising in young adults

The numbers are striking. A 2023 report from the American Cancer Society found that 20% of colorectal cancer diagnoses in 2019 were in patients under 55, roughly double the rate seen in 1995. Rates of advanced disease have climbed about 3% each year in people younger than 50.

A 2026 American Cancer Society study published in JAMA found that overall cancer mortality in Americans under 50 dropped 44% between 1990 and 2023. Colorectal cancer defied that trend, rising 1.1% every year since 2005. The disease moved from the fifth leading cause of cancer deaths in that age group to the first.

“We’re still seeing the trend, so it wasn’t temporary,” said Dr. Vikram Reddy, a Yale Medicine colorectal surgeon who was among the first to spot the pattern about 15 years ago.

Why doctors still don’t know what’s causing it

There is no confirmed explanation. Researchers have pointed to a familiar list of associated factors. Sedentary lifestyles, being overweight or obese, smoking and heavy alcohol use are all under scrutiny, along with diets low in fiber and diets high in fat or processed meats. Environmental exposures are also being investigated.

Genetics were an early suspect, but the evidence hasn’t lined up. Lynch Syndrome, the most common inherited condition tied to colorectal cancer, usually produces tumors on the right side of the colon. That is not the pattern doctors are seeing in these younger patients. Reddy said many of the young people diagnosed at Yale have sporadic cancers with no identifiable genetic syndrome.

“There may be other genes associated with predisposition for colorectal cancer that have yet to be discovered,” Jessica DiGiovanna, MS, a licensed certified genetics counselor with the Smilow Cancer Genetics and Prevention Program, told Yale Medicine. Scientists have mapped only about a third of the roughly 20,000 human genes.

Environmental influences are the current leading theory. “What’s alarming is that we don’t know what’s causing it. Right now, we think environmental influences are underlying the rise in incidence,” Sonia Kupfer, MD, a gastroenterologist and director of the Gastrointestinal Cancer Risk and Prevention Clinic, told UChicago Medicine.

Why colorectal cancer is often caught too late

Colon and rectal cancers frequently develop without any symptoms, so patients often have no idea anything is wrong until the disease is advanced. When symptoms do appear, they can look like less serious issues such as hemorrhoids.

Screening avoidance makes the problem worse. Many people skip colonoscopies because of the required bowel prep. Stool-based tests and an FDA-approved blood test called Shield by Guardant Health offer easier options, but any positive result still requires a follow-up colonoscopy. Kupfer noted that colonoscopy remains the only test that can both detect and remove precancerous polyps while also identifying cancer early.

Who faces the highest risk

Family history matters. Anyone with a personal history of polyps or a close relative who has had colorectal cancer faces elevated risk. Inflammatory bowel diseases like Crohn’s and ulcerative colitis also raise the odds, because chronic inflammation encourages abnormal growths.

“People need to talk to their families. Even if your mom had a non-cancerous polyp at age 40, you need to start screening for colorectal cancer younger [than 45],” Rebecca Siegel told NBC News.

Symptoms deserve attention at any age. Changes in bowel habits and rectal bleeding are common warning signs, along with abdominal pain and unexplained weight loss. Any of these should prompt a conversation with a doctor regardless of how young the patient is.

What the current screening guidelines say

The US Preventive Services Task Force recommends regular screening starting at age 45, lowered from 50 in 2021. Higher-risk patients may need to start earlier and screen more often. According to the CDC, routine screening could prevent one in three colorectal cancer deaths.

Researchers at Yale and elsewhere are working to identify new genes that could predict risk, while molecular tumor profiling helps guide treatment once cancer is found. Advocates are also pushing to lower the recommended screening age again.

What doctors want you to do

The message from specialists is simple. Don’t wait.

“If anyone has any change in their bowel habits, if they have any bleeding, even if they think it’s a hemorrhoid, and it doesn’t go away, just get a colonoscopy,” Reddy told Yale Medicine.

Kupfer echoed the point. “It’s not impossible for people in their 30s to get colon cancer. The best advice we can give is to not ignore any symptoms. If you notice blood in your stool, don’t just assume it’s hemorrhoids, talk to your doctor.”