Did you know that nicotine is as addictive as heroin or cocaine? If someone uses nicotine again and again, such as by smoking cigarettes or cigars or chewing tobacco, his or her body develops a tolerance for it. When someone develops tolerance, he or she needs more drug to get the same effect. Eventually, a person can become addicted. Once a person becomes addicted, it is extremely difficult to quit. People who start smoking before the age of 21 have the hardest time quitting, and fewer than 1 in 10 people who try to quit smoking succeed.
When nicotine addicts stop smoking they may suffer from restlessness, hunger, depression, headaches, and other uncomfortable feelings. These are called "withdrawal symptoms" because they happen when nicotine is withdrawn from the body.