It's a fact that many doctors not only smoke and drink, but take drugs as well. Why, well because of the stress they suffer from treating all those smokers, drinkers and drug addicted citizens.
One way to make your doctor feel ill, ask him for valium hehe. He'll then tell you can't have any because it's addictive (which is rubbish). The trouble is, most Doctors cannot tell you why some drugs are addictive and some or not. Cocaine, Heroin, Nicotine are addictive, because they affect the pleasure centres in the brain. Valium does not affect these centres, what it does in fact is to dampen down electrical activity on the GABA receptor cells. All the others affect Dophamine which is related to the pleasure sensation, for which your brain will want more and more.
Best
Ian