(NewsNation) — Doctors across the U.S. are trying to figure out what’s causing an alarming spike in colon cancer cases in young people.

The American Cancer Society estimates more than 153,000 people will be diagnosed with colorectal cancer (CRC) in 2023. Nearly 20,000 patients will be under 50. Those numbers have doctors predicting a 124% spike in colon cancer cases in patients ages 20 to 49 by the end of the decade.

According to an ACA study, the number of patients in the U.S. diagnosed with advanced-stage CRC increased by 8% from the mid-2000s to 2019. Diagnoses of patients under 55 increased from 11% to 1995 to 20%, or 1 in 5 people, according to the study.

Dr. Dana Hayden, a colon and rectal surgery specialist, said researchers study the trend, and some health professionals attribute the spike to several environmental factors “like diet, decreased exercise and poor lifestyle choices like increased smoking or drinking.”

“But there are definitely some other factors that could be related to genetics, that could be related to tumor biology,” she said. “So we are trying to work very quickly to figure this out.”

Less than two years ago, the screening recommendations for adults were lowered from 50 to 45 due to a rise among young and middle-aged people.

Hayden said the screening age could be decreased further in the future, but it’s key that physicians take patients’ concerns seriously and not overlook them because someone may not be 45.

Hayden said the most common CRC symptoms include:

• Blood in the stools or rectal bleeding
• Changes in bowel habits, like new diarrhea or new constipation
• Abdominal pain or the urgency to have a bowel movement

Yet, she said those symptoms are very nonspecific and may be related to other problems like hemorrhoids or other types of non-cancer-causing problems.

Hayden urges people to be aware that they could be related to cancer and it should trigger someone to mention it to a physician and start asking to get a colonoscopy.