in both European-American and African-American subjects and to look for replication in terms of identification of the same chromosomal regions between these independent samples (Drgon, et al., 2011; Q. R. Liu, et al., 2006; G. R. Uhl, Liu, & Walther, 2001). Other studies examined other samples including drug dependent individuals from the Baltimore site of the Epidemiological Catchment Area study (Johnson, et al., 2008), alcohol dependent samples from the Collaborative Study on the Genetics of Alcoholism (Johnson, et al., 2006), 2 samples of methamphetamine dependent individuals (G. R. Uhl, Drgon, Liu, et al., 2008), and nicotine dependent individuals (G. R. Uhl, et al., 2007).
