The effects of stress may stem from how your body responds to it. When you’re stressed, your body makes certain so-called “stress” hormones to deal with it. In many cancers, these hormones bind with cancer cells. That can make the cells more invasive and help protect them as they move from one part of the body to another. This makes it easier for the tumor to grow and the cancer to spread.

Stress also can affect your immune system. Studies show that stress interferes with the way certain cells in your immune system work. In particular, it affects cells that find and that kill emerging cancer cells.