1. Physical Health: Inhaling drugs like marijuana clearly is dangerous. If done enough, it can have the same effects that smoking cigarettes can cause. Marijuana has five times as much tar as the same amount of tobacco. Injecting drugs with needles, however, can be fatal in a shorter time. Consider that every time the addict uses a needle by another addict, fatal diseases like AIDS can be spread. Every day, someone uses a dirty needle and later finds that he has contracted a serious illness. Addicts will also be less inclined to exercise or take care of themselves when all that matters is getting the next high.
Addiction is when a person takes a drug constantly because they think they need it and find it very hard to stop. Dependence is when a person's body adapts to a drug so that the body is more resistant and starts craving the drug all the time - if a dependent person stops taking that drug, they may feel very sick, or rarely, even die without medical help. Addiction and dependence can happen separately to each other, and people can be come addicted to things that are not drugs (such as gambling , sex or just about any activity). Addiction and dependence can sometimes make it very hard for a person to live a normal life. Some psychoactive drugs are known to be very addictive (they often cause addiction: such as alcohol, heroin , tobacco , methamphetamine and cocaine ) whereas other drugs are known to be slightly less addictive (such as khat , cannabis and caffeine) or not addictive at all (such as LSD and Psilocybin mushrooms ).