Because of the reported relationship between NPY-LI expression and cocaine-seeking behavior (Boutrel et al., 2005; Menyhert et al., 2007; Wahlestedt et al., 1991), we tested for an association with cocaine dependence, defined by DSM-IIIR criteria. Due to the large number of cocaine dependent individuals who are comorbid for alcohol dependence (Table 1), we also analyzed individuals who met criteria for both DSM-IV alcohol dependence and cocaine dependence. Individuals who were neither alcohol dependent nor cocaine dependent were classified as unaffected for this phenotype. All other individuals were considered unknown. Since most cocaine dependent individuals were also alcohol dependent (208 out of 255), there was not a sufficient sample to analyze cocaine dependence excluding alcohol dependence (n=47). To avoid confounding cocaine dependence and alcohol dependence, whenever evidence of association was found with both alcohol dependence and cocaine dependence (p<0.05), an additional analysis was performed which included as affected only those individuals who met criteria for DSM-IV alcohol dependence but did not meet DSM-IIIR criteria for cocaine dependence (Table 1). All cocaine dependent individuals who were not alcohol dependent (n=47) were classified as unknown for this alcohol-only phenotype. Thus unaffected individuals were defined as those who were neither alcohol nor cocaine dependent.
