Nicotine is one of the most addicting substances known. In fact, the risk of becoming dependent on nicotine following any tobacco use is higher than the risk of becoming dependent on alcohol, cocaine, or marijuana. People who use several drugs often say that quitting tobacco is more difficult than giving up alcohol or cocaine.

Nicotine affects the functioning of the central nervous system, which is made up of the brain and spinal cord. Repeated use of nicotine results in tolerance, and the individual must use higher doses of the drug to obtain the same effects that first occurred at lower doses. As the body becomes tolerant to nicotine's effects, it becomes dependent on nicotine for normal functioning. Removal of nicotine from the body results in feelings of dysphoria. The individual needs to continue using nicotine to feel well and to function normally.

Nicotine Tolerance and Dependence