Definition of Nicotine addiction and withdrawal:

Tobacco and nicotine have a potential for addiction that is similar to alcohol, cocaine, and morphine.

Nicotine withdrawal creates anxiety, irritability, headache, hunger, and a craving for cigarettes or other sources of nicotine. These symptoms occur when a nicotine-dependent person suddenly stops smoking or using tobacco, or cuts back on the number of cigarettes or amount of tobacco products used.

See also: Smoking - tips on how to quit

Causes, incidence, and risk factors:

Tobacco is a plant grown for its leaves, which are smoked, chewed, or sniffed for a variety of effects.

• It is considered an addictive substance because it contains the chemical nicotine.
• Tobacco also contains more than 19 known cancer-causing chemicals (most are collectively known as "tar") and more than 4,000 other chemicals.

More than 38 million people in the United States have successfully quit smoking. Yet there are still around 50 million Americans who smoke. Most say they would like to quit.

Although the number of cigarette smokers in the United States has dropped in recent years, the number of smokeless tobacco users has steadily risen. Smokeless tobacco products are either placed in the mouth, cheek, or lip and sucked or chewed on, or placed in the nasal passage. Nicotine absorption from smokeless tobacco is similar to smoking tobacco, and addiction is still very strong.

Both smoking and smokeless tobacco use carry many health risks. See: Making the decision to quit tobacco.

Almost all people who try to quit have some form of nicotine withdrawal. Generally, people who smoked the longest or smoked a greater number of cigarettes each day are more likely to have withdrawal symptoms. Withdrawal symptoms are both physical and psychological.

People who are regular smokers tend to have particularly strong cravings. Their withdrawal symptoms get worse at certain times, places, or situations associated with smoking.