Nicotine dependence — also called tobacco dependence — is an addiction to tobacco products caused by the drug nicotine. Nicotine dependence means you can't stop using the substance, even though it's causing you harm.
Nicotine produces physical and mood-altering effects in your brain that are temporarily pleasing. These effects make you want to use tobacco and lead to dependence. At the same time, stopping tobacco use causes withdrawal symptoms, including irritability and anxiety.
While it's the nicotine in tobacco that causes nicotine dependence, the toxic effects of tobacco result from other substances in tobacco. Smokers have much higher rates of heart disease, stroke and cancer than nonsmokers do.
Regardless of how long you've smoked, stopping smoking can improve your health. Many effective treatments for nicotine dependence are available to help you manage withdrawal and stop smoking for good. Ask your doctor for help.