Smoking also facilitates nicotine dependence through sensorimotor factors associated with the act of smoking. Several studies have found that sensorimotor factors play an important role in maintaining smoking behavior in some smokers (Brauer et al. 2001; Naqvi and Bechara 2005; Rose 2006; Rose et al. 2000, 2003). A number of researchers, including Rose and colleagues, have used nicotinized and denicotinized cigarettes to study the separate roles of pharmacological actions of nicotine and the sensory/behavioral aspects of cigarette smoking on smoking withdrawal and smoking behavior (Rose et al. 2000). The results of those studies indicate that smoking denicotinized cigarettes can produce satisfaction as well as psychological rewards and can reduce the craving sensations. This finding is consistent with reports from smokers who described positive feelings as they inhale cigarette smoke but who do not experience these feelings when these sensory effects are blocked (Rose 1988; Rose et al. 1999). It has been suggested that the stimulation of nicotinic receptors on vagal nerve endings in the respiratory tract plays a role in mediating the immediate subjective effects of cigarette smoking (Rose et al. 1999).
The findings from this body of work thus suggest that airway sensory replacement may be an important aspect to be considered when determining the smoking cessation strategies to be used for some smokers (Rose et al. 1999; Westman et al. 1995).
In recent years, a body of research literature on the genetics of tobacco use has emerged. Over the past decade, researchers have cast some light on the role of genetic factors in tobacco use and dependence (Hall et al. 2002; Kendler et al. 1999; Lerman and Berrettini 2003; Li 2003, 2006; Madden et al. 1999; Sullivan and Kendler 1999). A review of a number of studies with twins suggests a significant genetic component in the initiation and maintenance of tobacco use (Kendler et al. 1999; Sullivan and Kendler 1999). On the basis of findings from studies of families, adopted children, and twins, Sullivan and Kendler estimate that a genetic influence may contribute approximately 60 percent to the possibility of smoking initiation, with environmental and personal influences contributing the remainder (Sullivan and Kendler 1999). Genetic influences are also estimated to contribute significantly (about 70 percent) to nicotine dependence.
Tyndale (2003), meanwhile, has reported on differences in the estimates of genetic influences on smoking initiation by gender, with rates ranging from 32 to 70 percent among females and 31 to 61 percent among males (Tyndale 2003). Estimates of the genetic influence on smoking persistence range from 4 to 49 percent among females and from 50 to 71 percent among males. Additional studies indicate that the age of smoking onset, the amount smoked, and smoking persistence are also influenced by genetics (Heath et al. 1999; Koopmans et al. 1999; Madden et al. 1999).