The question of nature vs. nurture has been the focus of many debates, especially within the discipline of psychological sciences. This paper will examine the views that exist regarding the importance of contributions to the risk of addiction, specifically, genetic (nature) vs. environmental (nurture) contributions through a review of the existing literature.
The nature-based view is that expression of addiction (phenotype) is based upon genetic predisposition (genotype). Numerous genetic studies on pedigree have been conducted over the years. The majority of the results of these studies indicate that monozygotic twins have higher concordance of addiction than dizygotic twins. More specifically, the more genes shared, the more similar the propensity for addiction.
Early studies genetic studies of addiction were family-based, which provided some initial clues regarding potential heritability of addictive disorders by examining the risk of substance abuse disorders by first-degree relatives of individuals who had either a substance abuse disorder or no substance abuse disorder. A study was conducted by Bierut et al. (1998), which produced results indicating that relative to a control individual, the siblings of alcohol-dependent probands had elevated rates of alcohol dependence. However, family designs are incapable of distinguishing whether the cause of familial similarity is genetic or environmental.
Adoption studies have also been utilized in addiction research related to genetics. Adoption studies involve the comparison of the concordance and correlation between offspring behavior (e.g. alcohol dependence) and the characteristics of both the biological and adoptive parents. Similarity observed between the offspring and biological parents is suggestive of genetic influences on behavior (Agrawal & Lynskey, 2008). One of the earliest adoption studies was conducted by Goodwin et al., (1973). Results of the study showed that men whose parents were alcoholics had an increased likelihood of alcoholism, even when adopted and raised by non-alcoholic parents from birth. The results provided strong support for a genetic component to alcohol dependence, as treatment for alcohol problems (9% versus 1%) and meeting criteria for alcoholism (18% versus 5%) were all significantly higher in the adopted-away children of parents with alcohol problems/ dependence (Goodwin et al., 1973).
Lastly, Cadoret et al. (1996) conducted one of the first studies that was in fact able to isolate the influence of environmental exposures from potential genetic confounds. In addition to family studies and adoption studies, there have been numerous large-scale twin studies with the aim of examining the role of genetics in susceptibility to addiction. However, the majority of the twin studies conducted have examined the heritability of alcohol abuse and dependence and have not examined the heritable influences on illicit drug use disorders. Past...