Most drugs not only have serious side effects; they dont even have their intended effect. An example is DES. It was given to millions of women to prevent miscarriage . It caused a large percentage of children who were exposed as fetuses to be sterile . It was later determined that it actually increased the chance of miscarriage.
Most cases of Parkinson's are side effects of medications.
You are no more likely to survive cancer if you take chemo than a placebo but chemotherapy is a billion dollar business.