Fourth, shared environmental effects on the latent factors were more important at younger ages, and new effects almost disappeared in young adulthood. Fifth, these effects demonstrated evidence of stability and developmental attenuation. As illustrated in Fig. 2b, shared environmental factors at age 13–14 (shown in gray) accounted for 53% (18% out of a total of 34%) of the variance at age 16–17 and 47% (9% out of a total of 19%) at age 19–20. A small amount of new effects were introduced at age 16–17 (shown in dark gray). Finally, total common unique environmental effects also remained similar across development, being estimated at 13, 12 and 18% respectively, and showed almost no continuity.
