A team of Australian specialists has debunked the theory that a positive attitude can boost the chances of surviving cancer.
The researchers said that they know their study findings might not impress the majority of patients who believed their outlook could help their diagnosis, but said it could be good news too.
"People often really beat themselves up and blame their attitude if their cancer relapses," News.com.au quoted Professor Kelly-Anne Phillips, a medical oncologist at the Peter MacCallum Cancer Centre in Melbourne, as saying.
"We've shown absolutely that you're not at fault. You cannot influence your cancer with positive or negative thinking, depression, a fighting spirit, or any other factor.
"That should be reassuring, but I guess it could cut both ways," she added.
For the study, researchers recruited 708 women who had been newly diagnosed with localised breast cancer and tracked them over eight years to see whether their cancer relapsed.
They found that a quarter died over the period.
During the study, researchers also assessed levels of depression, anxiety and other factors like fatalist outlook, avoidance, anger, and feelings of hopelessness.
"Essentially the bottom line is we didn't find any correlation at all between these issues and whether their cancer came back. This goes against what the vast majority of patients believe," Phillips said.
Phillips said that women who had an anxious preoccupation with their cancer were more likely to relapse but once the researchers adjusted for all the things known to cause recurrence, like size and grade of the tumour, this association disappeared.
"The women who were anxiously preoccupied were the ones that had the worst tumours, so they were anxious and preoccupied for a reason," she said.
She added that women may not like the news as it might make them feel like they have little control of their outcome, 'but it's important to see the upside too'.
Professor Ian Olver, Cancer Council Australia chief executive, said he had been involved in a smaller study in lung cancer that reached a similar conclusion.
"A positive attitude is great and it clearly helps quality of life when you're going through treatment but it makes an undetectable difference to disease," he said.
The findings were presented at a major cancer conference in Chicago.