Western Undergraduate Psychology Journal

Article Title

The A1 Allele of the Taq1 A Polymorphism in Association with Addiction: A Review


Substance abuse occurs when individuals move from voluntary drug use to compulsive drug use despite significant costs to their social, psychological, and physical well-being. Considering the adverse effects of compulsive drug use, an investigation of biological and environmental factors that make individuals susceptible to addiction becomes very useful. This paper will investigate one possible biological factor that influences addiction, specifically, I review the literature on the A1 allele of the Taq1 A polymorphism of the DRD2 gene. The literature on the association between the A1 allele with alcoholism reveals that the A1 allele is more prevalent in alcoholics versus non-alcoholics. However, the A1 allele does not seem to be a susceptibility factor specific to alcoholism, but it may be associated with a predisposition to addictive and impulsive behaviours in general. Next, the literature on the association between the A1 allele and addictive and impulsive behaviours in general will be reviewed. In addition, this paper attempts to find a theoretical framework that explains the A1 allele’s association with addictive and impulsive behaviours. In doing so, I will discuss the hypodopaminergic hypothesis and how the A1 allele may make individuals susceptible to experiencing a hypodopaminergic state. The hypodopaminergic hypothesis states that individuals who are predisposed to addiction have reduced dopamine (DA) levels (a hypodopaminergic state); and in order to alleviate this hypodopaminergic state, they are motivated to seek positive reinforcers in an attempt to increase DA levels. I review evidence that supports the hypodopaminergic hypothesis by demonstrating an association between the A1 allele and inefficient D2 receptor functioning. This inefficient D2 receptor functioning may lead to a hypodopaminergic state that motivates individuals to seek drugs and other addictive behaviours to increase DA levels.

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