> Most people who ask their doctor about a drug they saw on TV have the disease. Of those, a small percentage were undiagnosed, thus the TV commercial helped them with self-diagnosis.

This is one of the things driving the US rates of over testing, over diagnosis, and over treatment. Some people are helped, but many are harmed. See, for example, prostate cancer. Many men die with, not of, prostate cancer. The treatment for prostate cancer can be aggressive and can seriously degrade quality of life.