In a 10-year study, a team at Ohio State University found that breast cancer patients in a good psychological support group reaped dramatic physical benefits too.
The idea that such therapy can extend survival in cancer patients has been controversial for two decades. Past studies have yielded conflicting results.
Researchers led by Ohio State University's Barbara Andersen studied 227 women with breast cancer. About half took part in a year of therapy in groups of eight to 12 patients led by two clinical psychologists, while the others did not.
After 11 years, the women who participated in the group therapy has stronger immune systems, and were 45 per cent less likely to have their cancer return.
In addition, they were 56 percent less likely to die of breast cancer, the researchers wrote in the journal Cancer.
Andersen said the group sessions, among other things, aimed to reduce the women's distress, train them how to relax and improve coping skills, improve their diet and exercise habits and discourage smoking and drinking alcohol.
The improved survival may stem from better immune function resulting from stress reduction, the researchers said.
The therapy sessions began after the women had breast cancer surgery but before they started chemotherapy and radiation treatments. They took part in weekly sessions for four months and monthly sessions for another eight months.
Among the 54 women who died during the study period, those who took part in group therapy lived longer than the others. And among the women whose cancer came back, the recurrence happened later in those who had done the therapy sessions.
Lois Friedman, a psychologist at University Hospitals Case Medical Center's Ireland Cancer Center in Cleveland, said too few cancer patients take part in therapy. She hopes this study will encourage more to participate, knowing that it really makes a physical difference.
"Survival is kind of the bottom line when it comes to cancer. So we have people being healthy, productive people for longer -- and that's a huge health outcome," Andersen, who helped lead the therapy groups, said in a telephone interview.
Michael Stefanek, an American Cancer Society behavioral research expert, expressed wariness.
"Psychological interventions have been found in the majority of well-controlled studies to enhance quality of life and reduce distress. It would not be reasonable for patients to participate in psychological interventions with the goal of extending survival," he said in a statement.
But Marsha Scanlin, a breast cancer survivor, is thankful, "I came out tobe such a better person after having gone through that. I look at it as it helps me keep things in perspective, it helps me not sweat the small stuff."
Researchers say similar programs can help anyone fighting cancer.