People who have never married are significantly more likely to develop cancer than those who are or have been married, and for some cancer types, the gap is striking.
That’s the finding of a recent study from the University of Miami Miller School of Medicine. Researchers analyzed more than 4 million cancer cases across 12 states from a population of more than 100 million people, covering the years 2015 to 2022.
The findings show that men who had never married were about 70% more likely to develop cancer than married men. Women who had never married were about 85% more likely to develop cancer than women who were or had been married.
For specific cancer types, the gaps were even wider:
Anal cancer in men: Never-married men had roughly five times the rate of anal cancer compared with married men.
Cervical cancer in women: Never-married women had nearly three times the rate compared with women who were or had been married.
Ovarian and endometrial cancers: Married women had lower rates, partly because marriage is associated with higher rates of pregnancy, which has a known protective effect for these cancers.
Both anal and cervical cancers are strongly linked to an infection from the human papillomavirus (HPV), so the higher rates among never-married adults likely reflect differences in exposure and, in the case of cervical cancer, lower rates of screening and prevention.
Who was included — and who wasn’t
The study covered cancers diagnosed in adults 30 and older. Researchers put participants into two groups: those who were or had been married (including divorced and widowed individuals) and those who had never married.
The study’s timeframe starts in 2015 as that’s when the U.S. Supreme Court legalized same-sex marriage, which allowed the researchers to include same-sex couples in the married category.
One in five adults in the study had never married.
The study didn’t include people who are unmarried but in committed partnerships, a group the researchers acknowledge is worth exploring in the future.
Cancer types and racial patterns
The strongest associations between never-married status and higher cancer rates appeared in cancers tied to infection, smoking or alcohol use. The links were weaker for cancers with well-established screening programs, including breast, thyroid and prostate cancers.
Race also played a role. Black men who had never married had the highest overall cancer rates in the study. But married Black men had lower cancer rates than married white men, suggesting that marriage may carry a particularly strong protective association for that group.
The researchers also found that the gap between married and never-married adults widened with age, which suggests that the health benefits associated with marriage may build over time.
What the research shows
The study’s authors are careful to say that marriage doesn’t magically prevent cancer.
Frank Penedo, Ph.D., associate director for population sciences at the Sylvester Comprehensive Cancer Center, which is part of the University of Miami Miller School of Medicine, explains in a summary of the findings:
“It means that if you’re not married, you should be paying extra attention to cancer risk factors, getting any screenings you may need and staying up to date on health care.”
People who marry may tend to smoke less, drink less and be more socially connected, factors that independently lower cancer risk. Still, the researchers say the signal is clear enough to warrant attention.
“With the prevalence of marriage decreasing in the U.S., this is something that should be further studied,” said co-author Dr. Paulo Pinheiro, a professor of cancer epidemiology at the Miller School.