Tobacco smoke can cause many cancers, methamphetamine can cause severe dental problems, known as meth mouth, and opioids can lead to overdose and death. Drug use may trigger or worsen mental health conditions, particularly in people with specific vulnerabilities. Cigarettes are legal to purchase, but drug-addictive people can fill the cigarette with illegal drugs like heroin or other harmful substances. I saw my father use a powder-like thing called heroin, and he would sometimes put it in a cigarette or inhale it through his nose. There may be a minimal benefit in a few substances, but most of them just kill the person who uses it and destroys families.