if they used cannabis [31]. Similarly, in a randomized, double-blind, placebo-controlled study, carriers of the Val allele were more sensitive to Δ9-THC-induced psychotomimetic and amnestic effects than Met carriers, but this was conditional on psychometric evidence of psychosis-proneness [94]. Unlike Caspi et al. [31], Zammit et al. [240] failed to find evidence supporting differential effects of cannabis use on psychosis risk according to variation of the COMT gene.
