May 15 (HealthDay News) -- Group psychotherapy does not help extend the lives of cancer patients, new U.S. research concludes.

The University of Pennsylvania School of Medicine paper contradicts the findings of some previous studies.

"We all wish that psychotherapy could prolong life, because it appeals so strongly to firmly rooted notions that a person should be able to control their destiny," study author James C. Coyne, co-leader of the Cancer Control and Outcomes Program at the Abramson Cancer Center and a professor of psychology in the university's department of psychiatry, said in a prepared statement.

However, he believes that he and his colleagues "have a special responsibility to cancer patients to clarify that the reasonable goal of psychotherapy and support groups is to improve their quality of life, not extend it."

The authors conducted an extensive review of past research. They concluded that there is no compelling evidence of an association between psychotherapy or support groups and cancer patients' survival.

The paper is published in the May issue of Psychological Bulletin.

According to background information in the article, about 25 percent of cancer patients believe there is scientific evidence that group therapy will extend their lives.

But Coyne said that studies suggesting that psychotherapy helps prolong cancer patients' lives had numerous methodological and analytical flaws.

He noted that researchers often redefined the purpose of their studies after looking at the data they'd already collected on patients.

"If these studies had been testing medications, rather than psychotherapy, no one would have paid much attention to the redefined outcome of improved survival, and leading medical journals would probably not have accepted the papers, given their other flaws," Coyne said.