Nicotine dependence is an addiction to tobacco products caused by the drug nicotine. Smoke from cigarettes, cigars and pipes contains thousands of chemicals, including nicotine. Smokeless tobacco also contains 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 spur your continued use of tobacco and lead to dependence. At the same time, quitting tobacco use causes withdrawal symptoms, including irritability and anxiety.

Nicotine dependence brings a host of health problems. While it's the nicotine in tobacco that keeps you hooked, the toxic effects come mainly from other substances in tobacco. Smokers have significantly higher rates of heart disease, stroke and cancer.