Model IV dropped A1 from the model (Fig. 1B), thereby testing if the genetic influences on AD and AC were entirely unrelated. This model failed badly, producing a very poor fit (AIC = +82.9). Model V dropped A2 from the model (Fig. 1C), thereby testing if a single common genetic factor could explain all the sharing of genetic influences between AD and AC. This model fit moderately worse than model II (AIC = −20.5 vs. −24.2). Model VI dropped A3 from the model (Fig. 1D), thereby testing if all of the genetic influences on AD were shared with our AC measures. This model fit better than model II (AIC = −26.1) and was thereby our best-fit model.
