e 80s that involved several factors including a biological predisposition. In a recent revision of this earlier theory (Blum, Cull, Braverman & Comings, 1996) he and his colleagues have expanded their theory to include various behavioural disorders including alcoholism, substance abuse, smoking, compulsive overeating, attention deficit disorder, Tourettes syndrome and even pathological gambling. The authors state: We believe that these disorders are linked by a common biological substrate, a hard-wired system in the brain (consisting of cells and signaling molecules) that provides pleasure in the process of rewarding certain behavior (Blum et al., 1996 p.132). A theory that would integrate this many previously different syndromes would be clearly extremely important as it could lead to similar methods of prevention and treatment. Moreover, Blum believes that the common thread running through these behaviors is a dysfunction in the brains pleasure and reward system, one involving the neurotransmitter Dopamine usually present in the limbic system. Essentially he suggests that the use of several drugs and the expression of several compulsive behaviours are caused by the brains attempt to compensate for a deficient, hypoactive reward system. Furthermore, Blum believes that the genetic site that leads to the dopamine deficiency is the A1 allele. Henceforth, he suggests that the best hope of preventing these disorders is to increase genetic testing so that individuals who have the A1 allele can be counseled early on in life to avoid behaviour that could put them at risk (Blum et al., 1996).Clearly, as science and medicine have advanced in their understanding of genetics, it has become clear that many complex problems such as alcoholism, there is usually more than one gene responsible for the problem. Furthermore, identifying the genes that lead to alcoholism and drug addiction in humans has been difficult, since humans express more than...
