As a child, researcher Surendranath Shastri, M.D., D.Ph., worshiped his dad. “He was a lifetime smoker, so I thought it was cool to smoke,” says Shastri. “I started smoking around age 18, about the same time I started medical school.”

By his early 20s, Shastri was smoking two packs of cigarettes a day. He lived in India, where smoking was a big part of the culture. Shastri recalls cigarettes were given as a party favor to guests...