The twin work also showed that shared environment from year 1-2 predicted 10% of the variance in adult GCA, highlighting the lasting impacts of the infant environment.

Thank you to all our coauthors and the Colorado Longitudinal Twin Study participants. 4/4

We used twin studies & polygenic indices (PGIs/PGSs) which showed a rapid increase in the stability of GCA between ages 1 and age 7. Half of the variance in adult GCA was explained by genetic influences at age 7 or earlier, and two-thirds was explained by genetic influences at age 16 or earlier. 3/4

Two measures of infant cognition (a test of novelty preferences and tester-rated task orientation) given at age 7 and 9 months predicted general cognitive ability (GCA) nearly 30 years later. 2/4

Twin analysis show the association between brain age and EF decline was explained mostly by genetic influences and some nonshared environmental influences. Brain age is highly heritable (~62%), but heritability of EF changes are much smaller (19%)

APOE also predicts of executive function changes between 56 and 68, but it did not interact with brain age. Cognitive reserve also did not interact with brain age to predict EF changes.

I'm curious what others think, but I feel we need to be more careful about including 'proxy' phenotypes in big GWASs of psychiatric disorders. The power for some genetic effects is definitely better but it may wash our or even hide other important genetic variation

There are a lot of dimensions mixed in the could cause differences (self-report vs. clinician, continuous ratings vs. case-control, etc.), but our findings are consistent across GWAS and twin/family approaches