However, the selection of genetic information for incorporation into a prevention study is not straightforward. Some studies focus on specific variants within a candidate gene with demonstrated or purported functional relevance.(Caspi et al., 2002; Caspi et al., 2003) Other studies systematically genotype genetic variation across a gene of interest, with the rationale that there could be multiple locations in the gene that alter function, and accordingly, risk1 (Carlson et al., 2004; Dick et al., 2008). In other words, there could be a compelling rationale to study a particular gene, but what variants in that gene are likely to be relevant remain unknown(Zheng et al., 2016). The biological rationale for focusing on any one gene can be problematic at best, as delineated in Cleveland et al (2017), in this issue, as can identifying a particular allele as a “risk” allele. In truth, we are only studying genetic variation, not genetic “risk”, and though an allele may be associated with a deleterious outcome, for example substance use, it may be conferring risk via a mechanism such as sensation-seeking, which is in itself
