To find out, the researchers analyzed a large dataset covering 12 states that included demographic and cancer data from more than 4 million cancer cases in a population of more than 100 million people, collected between 2015 and 2022. They examined cases of malignant cancers diagnosed at age 30 or older and compared rates of various cancers by marital status, further broken down by sex and race and adjusted for age.
The researchers categorized marital status into two groups: those who were or had been married, including married, divorced and widowed individuals, and those who had never been married. The study began in 2015 because that year, the U.S. Supreme Court legalized gay marriage, allowing same-sex couples to be included in the married category. One in five adults in the study had never married.
Dr. Pinheiro expected to see some associations, given established relationships between marriage and lifestyle factors such as smoking, routine medical care and having children. But the strength of some findings surprised him.
Adults who were never married had substantially higher rates of developing cancer compared with those who were or had been married. For some cancers, the association was even stronger: adult men who were never married had approximately five times the rate of anal cancer compared with married men. Adult women who were never married had nearly three times the rate of cervical cancer compared with women who were or had been married.
Both anal and cervical cancers are strongly related to HPV infection, so these differences likely reflect variation in exposure and, for cervical cancer, also differences in screening and prevention. In contrast, for cancers such as endometrial and ovarian, differences by marital status may partly reflect the protective effect of parity, which is more common among married individuals.
“It’s a clear and powerful signal that some individuals are at a greater risk,” Dr. Penedo said.
Men and women showed slightly different patterns. Men who were never married were about 70% more likely to develop cancer than married men. Women who never married were about 85% more likely to develop cancer than women who were or had been married.
This represents a small but noteworthy reversal of a broader trend. Men often benefit more from marriage than women in terms of health and social factors. In this case, women appeared to benefit slightly more from marriage than men.
Cancer Types and Racial Patterns
The strongest associations between marriage and cancer were seen for cancers related to infection, smoking or alcohol use and, for women, cancers related to reproduction, such as ovarian and endometrial cancer.
The researchers found weaker associations for cancers with robust screening programs, including breast, thyroid and prostate cancers.
They also observed patterns across race and marital status. Black men who were never married had the highest overall cancer rates. However, married Black men had lower cancer rates than married white men, indicating a strong protective association with marriage in that group.
Study Limitations and Next Steps
The study has limitations. People who smoke less, drink less, take better care of themselves and are more socially integrated may also be more likely to get married.
Still, the researchers found that associations between marriage and cancer were stronger in adults older than 50, suggesting that, as people age and accumulate cancer risk exposures, the benefits associated with marriage may become more pronounced.
The study also excluded individuals who are unmarried but in committed partnerships. That group is likely small relative to the size of the dataset, Dr. Pinheiro said, but worth exploring in future research.
Future studies could further subdivide the married category into married, divorced and widowed individuals and follow people over decades to better understand how marital transitions affect cancer risk.
Overall, getting married does not magically prevent cancer, both Dr. Pinheiro and Dr. Penedo stressed.
“But the association between marriage status and cancer risk is an interesting, new observation that deserves more research,” Dr. Pinheiro said.
Reference: Pinheiro PS, Balda AN, Cranford HM, Crane TE, Kobetz EN, Penedo FJ. Marriage and cancer risk: A contemporary population-based study across demographic groups and cancer types. Cancer Res Comm. 2026;6(4):783-791. doi: 10.1158/2767-9764.CRC-25-0814
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