Vulnerabilities Underlying Human Drug Dependence: Goal Valuation Versus Habit Learning
There are two steps towards becoming a drug addict, according to Bardo, Donohew, and Harrington (1996). The individual must ®rst try the drug recreationally and then he or she must continue to use the drug to the point where mounting harms justify the clinical diagnosis of dependence. Whether or not an individual tries a drug in the ®rst instance appears to be a function of a number of demographic and psychosocial factors such as drug availability in the neighbourhood; accepting attitudes among parents, siblings, and peers; expectancies concerning the likely pleasurable effect of the drug; as well as disobedient and undercontrolled temperament (Hawkins, Catalano, & Miller, 1992; Kirisci, Vanyukov, & Tarter, 2005; Leventhal & Schmitz, 2006; Wagner & Anthony, 2002). However, these variables are not of concern in this chapter. Rather, we are interested in identifying how exposure to the drug interacts with the individual's psychological constitution, to drive the uptake and maintenance of drug use initially, and the perseveration of drug use longitudinally.