Total shared environmental effects decreased in importance. This same trend was shown for common shared environmental effects as these effects became almost non-existent by age 19–20. However, the trend was less consistent for alcohol intoxication-specific shared environmental effects. At ages 13–14 and 19–20 specific estimates were equal (3%) whereas there was a spike in these effects at age 16–17 (18%). The cross-time continuity of the residual shared environmental estimates was minimal.
