The nicotine in tobacco is addictive like heroin and cocaine which makes it hard to stop smoking once you start. Overdoses of some drugs can and do kill. Illegal drug users can never be sure of the quality of drugs they are using. Frequent use of marijuana can lower hormones and affect physical or sexual development. It can also interfere with driving ability and coordination.
Cocaine CAN cause sudden death in otherwise healthy young people - even once can be fatal.
Crack, the most addictive form of cocaine, is also the most deadly. Because it is smoked rather than snorted, it reaches the brain much faster and in higher concentration. A teenage pregnancy is harmful to both parents and baby. There is NO cure. And, anyone can get infected.