Unstandardized and standardized variance/covariance matrices are available in Supplementary Table 2. The heritability of SELF increased from 0.03 at ages 12–14 to 0.46 at ages 22–25. Shared environmental influences correspondingly decreased over time, from 0.22 to 0.03. Unique environmental factors account for a substantial proportion of the total variance at each age range (0.43–0.75). Results for PEER were similar, though its heritability in early adulthood (0.33) was lower than for SELF. Shared environmental influences became less relevant over time (from 0.28 down to 0.09), while unique environmental influences were temporally stable (0.58–0.62).
