Evidence for genetic linkage to alcohol and other substance dependence in other areas of the human genome has also been reported with some consistency across studies. At least five studies have reported evidence for linkage of substance dependence to a broad area on distal chromosome 1 (Reich et al., 1998; Foroud et al., 2000; Nurnberger et al., 2001; Dick et al., 2002; Hill et al., 2004; Lappalainen et al., 2004; Guerrini et al., 2005; Ehlers and Wilhelmsen, 2006). A site on chromosome 4 near a GABAA receptor gene cluster was first identified as being associated with alcohol dependence by Long et al. (1998) in a southwest Indian tribe, and also by COGA (Reich et al., 1998). This chromosomal region, which contains genes coding for the GABAA receptor subunits GABRG1, GABRA2, GABRA4, and GABRB1, was also linked to an electrophysiological phenotype (EEG beta activity) that characterizes individuals at risk for alcoholism in the COGA study (Porjesz et al., 2002), heavy drinking in the Framingham study (Wyszynski et al., 2003), cannabis dependence in the nicotine addiction genetics project (Agrawal et al., 2008),
