It may very well be that alcohol trajectory classes are best understood as gradations on a continuum rather than highly disjunctive categories. Epigenetic developmental pathways linking gene products to complex behavior are numerous and distant, and research in this area generally yields evidence of small correlations between such causally distant variables. With many genetic and environmental forces at play—not to mention their nearly innumerable interactions and correlations—it is no surprise that such astonishing complexity should fail to neatly cohere into a small set of distinct developmental trajectories.
