Over the past few years, doctors and researchers have noticed a clear pattern: more young adults are being diagnosed with colorectal cancer—those under 50. On the surface, some of this surge can be credited to increased screening, especially following guideline updates that lowered the recommended starting age from 50 to 45. But deeper beneath those screening numbers lies a troubling reality: diagnoses among truly younger adults aren’t solely due to being screened earlier. That means we’re facing a bigger shift, one that demands fresh solutions.In 2018, the American Cancer Society recommended colorectal cancer screening begin at age 45—five years earlier than before. In 2021, the US Preventive Services Task Force followed suit. Unsurprisingly, this led to a jump in early-stage diagnoses among 45-to-49-year-olds.ACS data published in JAMA shows a steady increase in screening rates: from 20.8% in 2019 and 19.7% in 2021, rising to 33.7% in 2023 among that age group. A second ACS-led study tracked early-stage diagnosis rates—from 9.4 cases per 100,000 in 2019, to 11.7 in 2021, then 17.5 in 2022. That’s a 50% relative increase between 2021 and 2022. Experts note this trend largely reflects held-back cases being detected earlier thanks to broader testing.But that doesn’t chalk up the entire story. Colon and rectal cancers have been increasing steadily in younger adults—those under 45—for decades. This early-onset rise began in the mid-1990s and includes late-stage diagnoses—not just early detection.Who Is Getting Diagnosed?Doctors stress that while the decline in age recommendations helped some, it doesn’t explain the persistent rise in younger adults. In fact, research suggests annual case increases of 2–2.6% have occurred since 2012 among those under 50. In the 20–39 age group, incidence has been rising by around 1.6% per year since 2004.More than 20% of colorectal cancer cases now occur in adults under 55—double the rate from the mid-1990s. Alarmingly, this early-onset trend is contributing to colorectal cancer becoming the leading cause of cancer death among younger men and the second-leading cause among younger women. These are not always lifestyle-driven cases. Many patients are young, active, and with no known family history. As clinicians, many have expressed how unsettling it is to see so many seemingly healthy people presenting with aggressive tumors—and often at advanced stages. What Might Be Driving This Worrisome Surge?Researchers are testing multiple theories—but none yet fully explain the rise:Gut microbe toxins such as colibactin, produced by certain E. coli, are drawing attention. These toxins leave a specific DNA mutation fingerprint in early-onset tumors—over three times more common compared to cancers in older patients. Some studies suggest 15% of early-onset cases involve colibactin-driven mutations.Diet- and lifestyle-related risks remain central: obesity, processed meats, low-fiber diets, sedentary behavior, refined sugar, insufficient sleep, and environmental pollutants. One prominent study links higher birth and adolescent BMI with increased colon cancer risk later in life. Even every additional kilogram at birth above normal is tied to 9% higher colorectal cancer risk. Other suspected contributors include microplastics, antibiotic use, and artificial light exposure, although more conclusive evidence is pending. Symptoms You Should Never IgnoreCrucial to stopping this trend early is awareness. Here’s what to watch for—and not dismiss, even if you’re under 45:Rectal bleedingPersistent abdominal pain or crampingChanges in bowel habits or stool shapeUnexplained weight loss or appetite changesJessica Star of ACS—lead author on both new JAMA papers—warns, more than half of cases in younger adults occurred in those not yet eligible for screening. So symptoms matter, regardless of age. If you're dismissed with a benign diagnosis like hemorrhoids, consider a second opinion. How to Lower Your Risk?Screening matters. Most colorectal cancers begin as precancerous polyps, and removing these early saves lives. Current recommended options include:Annual or triennial stool-based fecal testsColonoscopy every 10 yearsVirtual colonoscopy every five yearsSigmoidoscopy every five yearsPromising new research shows that mailing stool test kits directly to eligible adults dramatically increases completed screenings—even more than simply offering choice. Yet, screening is still underused: more than 1 in 3 adults aged 45 and older report not getting screened as recommended. To reduce personal risk:Maintain healthy body weight and regular physical activityCut back on red and processed meats, refined sugars, and ultraprocessed foodsBoost fiber intake through plant-based nutritionAvoid tobacco and limit alcoholStay alert to symptoms and seek screening or evaluation promptly when indicatedIf you’re under 50—or even nearing that threshold—understand this: colorectal cancer is no longer just a disease of older adults. While earlier screening through age-lowering guidelines has helped catch many early-stage cancers in 45–49-year-olds, it doesn’t address the underlying, persistent rise in true early-onset cancer.The surge among younger adults signals something deeper—and possibly preventable—but only if we tackle it strategically. That means screening more women and men at the right age, investing in research, and making early testing easier and more equitable.As expert researchers remind us, we’re not merely diagnosing more cancers—we’re getting better at catching them earlier. But to save more lives, identify root causes, and reverse these trends, we must remain proactive. Not just for our generation—but for all who follow.