2 Answers

Depends on the medicine. I'm sure chemo does. 

There are very few medicines that are not influential regarding how a person thinks....If it had no influence whatsoever I doubt it would be around very long. Some folk think all disease comes from errorant thinking and that drugs are no more than magical elixers designed to bring about some form of destraction from their pain or shame. Magical thinking can work wonders for ardent beleivers as some apparently do.

Modern medicine,however, is based on double-blind studies and intensive research into the cause and cures of disease. It did originate from a witches brew of beliefs and denials untle we realized the fact that shoddy results in public trials was a result of errors in process testing the opinions of the folk doing the research. Double blind research has been revolutionary in medicine since the late 1950s.

Cancer is increasingly dealt with by applying the patients own immune system to the task, with miraculous success. In fact the cure rate can be so fast that patients express various strong emotions to the result of their treatment and curiously surving what was believed to be their approaching death. It can be quite a shock to survive what was thought to be their living end.