Examining the ‘upper portion’ of the model, six results are noteworthy (Table 3). First, illicit drug use becomes a better representative of the latent factor with increasing age whereas smoking and alcohol intoxication become less representative. Second, heritabilities for the common factors remained stable across development, estimated at 52% for age 13–14, 54% for age 16–17, and 53% for age 19–20. Third, these genetic effects demonstrated evidence for stable and dynamic risk. As illustrated in Fig. 2a, genetic factors at age 13–14 (shown in gray) accounted for a majority of the genetic effects at ages 16–17 and 19–20. However, innovation was also exhibited. Of the total genetic influences at age 16–17, 7% (4% out of a total of 54%) are new genetic factors (shown in dark gray), and at wave 4, 25% (13% out of a total of 53%) of the genetic influences are new factors specific to this age (shown in black).
