Fourth, while we conducted a system-level analysis, our gene-based testing did not reach statistical significance after Bonferroni correction. The single SNP that did survive correction, rs604300, is unlikely to be the only important variant within the eCB system. The balance between AEA (metabolized by FAAH) and 2-AG may be paramount to understanding eCB system contributions to psychiatric disorders and related brain function. A particularly fruitful future approach may be to examine evidence for epistasis using system-level analytic methods that do not rely on SNP-level priors or on the additive nature of the current approach (e.g., random forest regression trees; for review, see Upstill-Goddard, Eccles, Fliege, & Collins, 2013).
