Nicotine is the chemical in tobacco that keeps you smoking or chewing. Nicotine can be as addictive as cocaine. It increases the release of brain chemicals called neurotransmitters, which help regulate mood and behavior. One of these neurotransmitters is dopamine, which makes you feel good. Getting that dopamine boost is part of the addiction process. Nicotine dependence means you can't stop using the substance, even though it's causing you harm.

Anyone who smokes or chews is at risk of becoming dependent on tobacco and nicotine. Most people begin smoking during childhood or adolescence. The younger you begin smoking, the greater the chance that you'll become a heavy smoker as an adult. Children with two parents who smoke are twice as likely to become smokers. Children with friends who smoke also are more likely to try cigarettes.

Symptoms that you may be addicted to nicotine:

• You can't stop smoking or chewing tobacco. You've made one or more serious, but unsuccessful, attempts to stop.
• You experience withdrawal symptoms when you try to stop. Your attempts at stopping have caused physical and mood-related symptoms, such as strong cravings, anxiety, irritability, restlessness, difficulty concentrating, depressed mood, frustration or anger, increased hunger, insomnia, and constipation or diarrhea.
• You keep smoking despite health problems.
• You give up social or recreational activities in order to smoke or chew. You may stop going to smoke-free restaurants or stop socializing with certain family members or friends because you can't smoke or chew in these situations.

Factors that influence nicotine dependence include:

• Genetics. The genes you inherit do play a role in nicotine dependence. For instance, the fact that you will start smoking and keep smoking may be partly inherited. Some people experiment with smoking and never become smokers. They don’t experience pleasure from smoking. Other people become habitual, dependant smokers. Some "social smokers" can smoke just once in a while, and yet another group of smokers can stop smoking with no withdrawal symptoms. These differences can be explained by genetic factors that influence how receptors on the surface of your brain's nerve cells respond to nicotine.
• Depression, other mental illness and substance abuse. People who have depression, schizophrenia and other forms of mental illness are more likely to be smokers. It has been speculated that smoking may be a form of self-medication for these disorders. People who abuse alcohol and illicit drugs also are more likely to be smokers.

Smoke from cigarettes, cigars and pipes contain thousands of chemicals, including nicotine. Smokeless tobacco also contains nicotine.

If you've tried to stop smoking but haven't succeeded, talk to your health care provider about medications to help you quit. Look for a stop-smoking counselor, who can help you create a treatment plan that works for you. Most people who try to stop on their own don't succeed. You're more likely to stop for good if you follow a treatment plan that addresses both the physical and the psychological aspects of tobacco dependence.