Craving did not differ between genotype groups. Previously, we had found that, after marijuana abstinence, C/C individuals exhibited a greater increase in craving than A/A and A/C individuals (Haughey et al. 2008). It is possible that the current sample was too small to detect a change in this phenotype. Alternatively, the required period of abstinence may not have been long enough to induce changes in craving large enough to reveal this genotype interaction. While participants in our past study abstained for 5 days, we chose to require 24 h of abstinence in order to avoid conflating withdrawal with acute effects, and to maximize the magnitude of these effects. We wanted to ensure participants were “primed” to respond to marijuana, but were not overwhelmed by withdrawal symptoms.
