... 2001) Many theories focus on why particular individuals are more susceptible to alcohol addiction or dependence than others (Clapper et al 1995 cited in West, 2001; Johnson & Glassman, 1998). Individuals who are particularly susceptible to the effects of alcohol, whether biochemically, psychologically or socially, or in need of the effects of alcohol, would obviously be expected to be most at risk of alcohol abuse (West, 2001). Although most studies acknowledge a genetic contribution to individual vulnerability to alcoholism (alcohol abuse or dependence), only some focus directly on genetic susceptibility (Ferguson & Goldberg, 1997). Researchers use twin studies to estimate the proportion of variance in a measured behaviour, which is due the genetic makeup of the individual and that which is attributable to environmental factors, such as social background. This is commonly referred to as hereditability (h2) (Jang, Livesley, & Vernon, 1997). Gorwood, Limosin, Batel, Duaux, Gouya & Adès, (2001) ...

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