What is the relationship between cancer and stress?

Stress contributes to the symptoms of cancer, but is never a direct cause. Hypothetically, if you're sick, and you can't control your negative thoughts, the symptoms that are commonly attributed to that sickness will take a greater toll on your health. What's also interesting is that here in North America, doctors readily prescribe moderate-strength pain killers, like Tylenol #3, even when the situation doesn't necessarily prompt it. The reason behind it is that the time it takes to heal without pain is less than when there is pain; hence, if you can control the pain (or stress in this matter), you'll heal faster.