"In summary, nicotine is the most potent constituent associated with the reinforcing effects of tobacco. However, researchers have identified other constituents in tobacco and tobacco smoke that may be reinforcing or facilitate reinforcing effects of tobacco. Nicotine metabolites have also been identified as potential reinforcers or enhancers of the reinforcing effects of nicotine. Researchers have observed that in addition to nicotine and other constituents of tobacco and tobacco smoke, sensory aspects of nicotine and environmental stimuli also have a significant role in maintaining smoking behavior (Rose et al. 1993; Shahan et al. 1999; Caggiula et al. 2001, 2002b; Perkins et al. 2001d) (for details, see “Learning and Conditioning” later in this chapter)."


US Department of Health and Human Services. "How Tobacco Smoke Causes Disease: The Biology and Behavioral Basis for Smoking-Attributable Disease: A Report of the Surgeon General." Atlanta, GA: U.S. Department of Health and Human Services, Centers for Disease Control and Prevention, National Center for Chronic Disease Prevention and Health Promotion, Office on Smoking and Health, 2010, p. 113.