In England doctors are seeing the benefits of fly fishing for those that have recently had surgery for breast cancer. They believe that the motions of casting a fly rod have therapeutic benefits regarding lymph glands for those patients.
There's a very informative article about all this you can read HERE.
So now you have a scientific excuse to go fishing!! Don't ever let anyone tell you that you fish too much. If they do, just tell them you've got to fish to stay healthy!!