I think doctors actually don't always know. I've seen alcoholics given anti-depressants and other strong meds ---- prescriptions written by doctors. One I know very well --- had some kind of drug prescribed that gave her weird hallucinations so she quit taking them right away ---- but some people think if the doctor says to take certain pills, that's what they should do. Plus a lot of people don't realize that addictions aren't usually just to one particular substance, they think if they were addicted to antidepressants for example that something like a painkiller might still be safe.