For centuries people have wondered whether there is a link between stress and cancer, but there has never been any solid evidence to support this theory. Most of the studies on this issue have looked at breast cancer, and more than 10 of these found no link between stress and the risk of getting breast cancer. Studies that have looked at all kinds of cancer, not just breast cancer, have also found very little evidence for stress being an independent cause of cancer. It has been asserted that there may be a link between stress and cancer because some laboratory studies show that stress upsets the immune system – and that an impaired immune system may increase the risk of cancer. There is stronger evidence that stress can have indirect effects because people who are under stress may do things that increase their risk of cancer – such as smoking or drinking too much alcohol. Good health habits that we know can help to prevent cancer, like eating plenty of fruit and vegetables and getting enough exercise, may also fall by the wayside if you are stressed.