Not a great analogy honestly, you can drive a car your whole life and your odds of dying in a car accident are probably like 1%. Meanwhile your odds of dying, or at the very least having very serious health effects, from using hard drugs your whole life are basically guaranteed.
Both of you are somewhat right. Drug abuse causes an increased risk in getting a bad medical condition. However, if you always drive faster than you should and don't give a fuck about road laws(which is kinda the equivalent to abusing hard drugs) you might also end up in the hospital one day.