The lack of evidence for linkage disequilibrium accounting for our detection of multiple SNPs within both the COMT and DDC genes associated with sensation seeking suggests that dopamine-related candidate genes likely contain multiple markers that affect sensation seeking, rather than a single SNP (or other individual unit of genetic variation) of relatively large effect which is simply being “tagged” (due to inter-SNP correlations, i.e., linkage disequilibrium) by surrounding SNPs. The apparent overrepresentation of significant SNPs located in the gene DDC in the individual association tests might imply the relevance of production over receptor characteristics in sensation seeking. While our current results suggest this conclusion, it would require replication in future research before being considered a reliable finding. Future research should also include genes corresponding with other candidate systems, such as serotonin-related genes (e.g. Heck et al., 2009), that have also been implicated in the etiology of sensation seeking and associated traits.
