“The main takeaway is that marital status appears to be a strong marker of cancer risk at the population level,” says Paulo Pinheiro, MD, PhD, a coauthor of the study and a physician-scientist and cancer epidemiologist at Sylvester Comprehensive Cancer Center in Miami.
This doesn’t mean marriage itself can keep people from getting cancer. Instead, it reflects how differences in risk factors, lifestyle, and health can add up over time, says Dr. Pinheiro.
Never-Married Adults Had Higher Cancer Rates
For the new study, researchers analyzed cancer data from about four million U.S. cancer cases diagnosed between 2015 and 2022, focusing on adults ages 30 and older.
They compared people who had never married with those who had ever been married — a group that included married, divorced, separated, and widowed adults.
Because the study used legal marital status recorded in population data, same-sex marriages were included beginning in 2015, but the data did not allow researchers to distinguish between different types of partnerships, says Pinheiro.
Researchers found clear differences in cancer risk based on marital status:
- Never-married men had about a 68 percent higher likelihood of developing cancer than their ever-married peers.
- Never-married women had about an 83 percent higher likelihood of developing cancer.
- This pattern was seen across all racial and ethnic groups and all age groups, with stronger differences in adults age 55 or older.
- The association was slightly stronger in women, challenging the assumption that marriage provides greater health benefits primarily for men.
If confirmed with further studies, the findings may one day help doctors offer individualized cancer prevention recommendations, says Dr. Patel, who wasn’t involved in the study.
Unmarried Adults Are More Likely to Develop Preventable Cancers
The biggest differences in cancer rates were seen in types linked to preventable risk factors: infections, smoking or alcohol use, and reproductive history. For instance, compared with ever-married adults:
- Never-married men had about five times the rate of anal cancer of married or previously married men.
- Never-married women had nearly three times the rate of cervical cancer of women who were or had been married.
- Liver cancer rates were about 2.3 times higher and lung cancer rates about 2.1 times higher for all never-married adults.
- Colorectal cancer rates were about 2 times higher in never-married women.
- Ovarian and uterine cancers were about 2.4 times higher in never-married women.
- Breast cancer rates were about 1.7 times higher.
- Prostate cancer rates were about 1.5 times higher overall.
- Thyroid cancer showed smaller differences, ranging from about 1.2 to 1.6 times higher among all never-married adults.
How Might Marriage Lower Cancer Risk?
The study does not show that marriage itself protects against cancer, but it points to several factors that may help explain the link.
“Relationships, support systems, and access to care can all shape health over time,” says Kevin Johns, MD, the medical director of the psychosocial oncology program at the Ohio State University Comprehensive Cancer Center in Columbus.
“Marital status may be a quick way to estimate the total impact of many socioeconomic risk factors rolled up in one package,” says Dr. Johns, who wasn’t involved in the research.
Differences in exposure to infections: Both anal and cervical cancers are strongly associated with human papillomavirus (HPV). “A higher number of sexual partners can increase exposure to oncogenic [cancer-causing] viruses, which may partly explain higher rates of certain cancers such as cervical and anal cancer,” Pinheiro says.
The rates may also reflect differences in screening and prevention for cervical cancer, he adds.
Long-term health behaviors: Healthy behaviors — such as avoiding smoking, moderating alcohol use, maintaining a healthy weight, and reducing exposure to infections — are important in shaping cancer risk over time, says Pinheiro.
These findings support the idea that partners may positively influence health behaviors, which may reduce cancer risk, says Patel.
In one long-term study, people with higher levels of support from a partner were more likely to stay physically active and eat more fruits and vegetables over time, which are both associated with lower cancer risk, she says.
Reproductive factors: Pregnancy and childbirth are protective against endometrial and ovarian cancer, and married women are more likely to have children, Pinheiro says.
Loneliness and social support: “Loneliness has been associated with poorer health behaviors and lower healthcare engagement,” says Pinheiro. It may indirectly influence cancer risk through these pathways, although it is not a direct cause of cancer, he says.
“Partners can serve a critical role in helping people navigate the healthcare system to receive screening and other preventive care,” says Patel.
Strengths and Limitations of the Study
The study’s size and scope are among its biggest strengths, drawing on millions of people across diverse populations and a wide range of cancer types. But because it’s an observational study, it doesn’t prove that marriage itself lowers cancer risk. It also relies on marital status as a simplified category that does not capture relationship quality, social support, or cohabitation.
“Although marital status is an important predictor of health, being married doesn’t automatically protect you,” says Bert Uchino, PhD, a researcher and a professor of psychology at the University of Utah Health in Salt Lake City.
There are studies that show poor marriage quality is associated with negative health outcomes, says Dr. Uchino, who wasn’t involved in the study.
What This Means for You — Even if You’re Not Married
The key takeaway, no matter what your relationship status, is that many of the factors associated with lower cancer risk are modifiable, says Pinheiro.
He and Johns recommend the following actions to reduce your cancer risk.
- Go to the doctor regularly, and stay up-to-date with recommended cancer screening and vaccinations, including for HPV.
- Avoid smoking and limit alcohol use.
- Focus on protective habits like a healthy diet, regular exercise, and safer sex.
- Build strong social connections beyond marriage or primary partnerships.
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