Farrah Fawcett cancer tied to stress? Maybe, says Ryan O'Neal

(CBS) Did psychological stress cause the cancer that killed Farrah Fawcett? Ryan O'Neal's only an armchair diagnostician, but he thinks it's a possibility.

"There was turmoil during my love affair with Farrah, a lot of it caused by my family and my kids," O'Neal said in a recent interview with CNN talk show host Piers Morgan. "And I just think that if she had never met us, would she still be alive today? Because nobody knows what causes cancer."

O'Neal's right about no one knowing the precise cause of cancer, at least in any given individual. But scientists say it's not yet clear what role, if any, stress plays in the development of cancer. Though some recent studies have indicated a link between various psychological factors and cancer, a direct cause-and-effect relationship has not been proven, according to the National Cancer Institute.

Stress can certainly lead to unhealthy behaviors that might increase cancer risk, such as overeating, smoking, or abusing drugs or alcohol. But O'Neal indicated that those factors wouldn't explain why Fawcett was diagnosed with anal cancer in 2006.

"She didn't smoke, she didn't drink, she exercised every day, and she believed in good health," he said.

But Fawcett did have at least some risk factors for anal cancer. According to the American Medical Association, the cancer is more common among women and people over age 50, as well as in smokers, people who use drugs or have conditions that suppress the immune system, and in people who have multiple sex partners or engage in anal sex.

The National Cancer Institute has more on stress and cancer.