Living in 2026 is generally considered fortunate, as it’s a favorable time to be alive. People today enjoy better health than ever before, with longer life expectancies, reduced infectious diseases, and decreased mortality from most chronic illnesses when adjusted for age.
Cancer exemplifies this trend. Cancer rates have remained stable or decreased over the years, and cancer mortality—the likelihood of dying from cancer if diagnosed—has significantly declined. Many cancers that were once viewed as death sentences in the 1990s are now managed as chronic illnesses like diabetes or emphysema, thanks to advancements in treatment.
However, colorectal cancer in young people stands out as an exception to this positive trend.
While overall rates of colorectal cancer—which encompasses both colon and rectal cancers—have declined overall, a rise in cases among those under 50, considered young in cancer terms, has been observed. This increase has minimal impact on the overall number of colorectal cancer diagnoses, as the absolute number in younger age groups remains low. Nonetheless, the trend is perplexing.
Colorectal cancer rates tend to be lower in older adults, yet they are climbing among younger individuals, and the reasons for this remain unclear.
Various theories have been proposed. Some suggest that pesticides or herbicides like picloram are linked to colorectal cancer risk. However, this theory faces challenges. Picloram and similar chemicals are used less now than in the 80s and 90s. It’s unclear how they could contribute to higher cancer rates in a specific age group today.
“While rates of colorectal cancer – which includes both colon and rectal cancers – have fallen overall, there’s been a recent uptick in cases in people under the age of 50 which is considered young when it comes to cancer.” – Gideon Meyerowitz-Katz, Epidemiologist
Moreover, older individuals typically experience greater exposure to these chemicals due to looser past regulations. It’s likely that previous generations had more pesticide exposure than today’s youth. Environmental factors don’t fully explain the increase in young people.
The same issue applies to other environmental factors. Some have linked per- and polyfluoroalkyl substances (PFAS), known as ‘forever chemicals,’ to colorectal cancer. Yet, exposure to PFAS isn’t age-specific, and older individuals might have been more exposed than the younger ones now experiencing increased cancer rates. Finding a clear exposure explanation is challenging.
Known causes of colorectal cancer are generally more prevalent among older adults. Few environmental factors are more common today than in past generations. Obesity is another potential factor, as it is known to increase colorectal cancer risk, and younger people are more obese now than before.
However, this explanation isn’t entirely satisfactory since older adults are also more obese. Modeling suggests that only about 15 percent of colorectal cancer cases are attributable to weight gain.
The mystery deepens as the trend isn’t uniform across countries or regions. A 2019 study indicated that colorectal cancer rates among young individuals remained stable or decreased in nearly half of the countries examined. A 2025 study yielded similar results, further complicating the picture. It’s unclear why rates are rising in the UK and US but declining in Italy and Lithuania.
Testing might be the most plausible explanation for this complexity. While changes in screening recommendations are unlikely the primary cause of the increase—since screening guidelines have only recently expanded to younger age groups, but the trend dates back to the 1990s—they’re not the only healthcare changes in recent years. Young people may be more likely to undergo colorectal cancer tests for various reasons, affecting diagnosis rates.
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Additionally, how countries report data might play a role. Disease statistics refer to the measured rate of a condition, and improvements in cancer registries over time could explain why more young people are recorded as having cancer.
However, these theories are not entirely convincing, as they don’t account for the different impacts on younger and older people. While there is a noted increase in colorectal cancer cases among young people in some countries, the underlying cause remains elusive. Many explanations seem improbable, making it challenging to pinpoint the true reason.
Gideon Meyerowitz-Katz is an epidemiologist specializing in chronic disease in Sydney, Australia. He maintains a regular health blog focused on science communication, public health, and interpreting new studies. He has previously assisted ScienceAlert in analyzing the real science behind viral studies.
This article was fact-checked by Clare Watson and edited by Fiona MacDonald. While we pride ourselves on our process, we are only human. If you spot a mistake, please let us know.
