Yes, could be a problem with the liver cytochrome system - for some substances people are poor metabolisers because there is an enzyme missing (correct me pls) or people are rapid metaboliser and feel nothing from the worst drugs.
I'm one by myself. CYP3D6 and CYP 3A4 - thats wny my tolerance is so shitty high my doc told me. Most benzos really metabolized by CYP450, but because i'm mixing a lot - i dunno.