Two additional caveats regarding the replication are also worth noting. First, while the AA genotype appeared to have a stronger protective influence than the AG genotype in MOAFTS, this effect was not statistically significant nor replicated in CATS. Due to the smaller numbers in MOAFTS, it is not possible to discern whether this is an underpowered difference or a false-positive and future studies should contrast these genotypes (AA versus AG) before combining them. Second, while there was no association between abuse and anhedonia in AA/AG individuals, this association was significant in CATS. This is likely due to the higher rates of abuse in this sample and the power afforded by a continuous index of abuse. Nonetheless, future studies should examine the AA/AG subgroup carefully for these effects.
