differ in terms of rates of psychopathology or SES (Iacono et al., 1999). Twin families were excluded from participation if either twin had a cognitive or physical disability that would hinder their participation in the day-long, in-person assessment, or if they lived further than a one-day drive to the University of Minnesota. The sample is representative of the Minnesota population in terms of ethnicity and SES (Holdcraft & Iacono, 2004). Note that the total N for the current study differed slightly from that of Loney et al. (2007) given that the models in the current study relied on those with complete data at both time points.
