The fact that the incorporation of single variants from theoretically-based biological candidate genes remains the most widely used strategy in prevention research is in stark contrast to the current state of psychiatric and behavioral genetics, where large-scale gene identification efforts systematically scan variation across the genome in an intentionally atheoretical manner. This strategy evolved after candidate gene studies yielded inconsistent effects, and subsequent systematic scans of the genome indicated that many of the “classic candidates” that had been the product of extensive study based on hypothesized biological rationale, yielded no evidence of association with expected outcomes in larger, more powerful studies (Farrell et al., 2015). Accordingly, there is concern that the candidate gene studies that are commonplace in prevention studies will be viewed as naïve, with respect to the current state of the science in genetics. Genes are necessarily involved in complex biological systems, and the effect associated with any one genetic variant on a complex behavioral outcome is likely to be extremely small (O’Donovan, 2015).
