Despite these limitations, our findings suggest conserved
effects of interactions between AEA and CRH on amygdala
function in rodents and humans and highlight the value of
imaging genetics for translating preclinical findings to clinical
phenotypes. These data are further useful for understanding
how pharmacologic manipulation of the endocannabinoid
system may be harnessed to treat anxiety and serve as a
cautionary note on the potential importance of individual
differences (45,46). Our data suggest that relatively increased
AEA inhibitory tone moderates the anxiogenic effects of
increased CRH signaling through attenuated amygdala habit-
uation. As such, targeted facilitation of AEA inhibitory tone
(through FAAH inhibition) may decrease anxiety and promote
fear extinction in the absence of high CRH signaling but may
have paradoxical effects in the presence of increased CRH
signaling by pharmacologically increasing the dependence of
amygdala regulation on AEA-mediated inhibitory tone. Alter-
natively, however, it is possible that enhanced anxiogenic
effects of CRH in the context of high AEA may not simply be
explained by overall levels but by the increased ability of CRH
against this background to compromise AEA signaling by
increasing FAAH activity. Thus, FAAH inhibition may be even
more effective in the context of both high CRHR1 and AEA
signaling, as it may prevent the anxiogenic effects of CRH by
blocking the ability of CRHR1-stimulated increases in FAAH to
inhibit AEA. Research in rodents showing that stress-induced
anxiety and related phenotypes are prevented by pharmaco-
logically inhibiting FAAH is consistent with this interpretation
(3,5,9). Further pharmacogenetic research is necessary, how-
ever, to dissociate these proposed models and validate the
efficacy of FAAH inhibitors as a potential therapeutic treatment
approach.