To Örebro University

Twin research has suggested that genetic factors are important for ADHD. Likewise, a recent twin study in suggested that school achievement at age 16 could be attributed by 52–58% to genetic factors, 24–31% to shared environmental effects, and 11–18% to unique environmental effects. Polygenic risk scores (PRS) for educational attainment (EA) has been found to predict educational achievement and ADHD symptoms in children, and PRS for ADHD predicts educational outcomes in the general population. Few twin studies have explored the overlap between ADHD and school achievement, and no study has explored this overlap using school grades.

We linked parent rated DSM-IV ADHD-symptoms at age 9 and PRS for ADHD and educational attainment, from a sample of 11,242t wins in the Child and Adolescent Twin Study in Sweden, to measures of school achievement (e.g., GPA) from Swedish national registers. Multivariate twin modeling was used to estimate the heritability of each trait, and the genetic correlation between the traits. ADHD-symptoms correlated negatively with school performance,-0.30. The heritability of ADHD-symptoms and school achievement were estimated to 62 and 58 percent respectively. The genetic correlation between ADHD symptoms and school performance was estimated to -0.40 and the genetic contribution to the phenotypic correlation was 75 percent.

These findings suggest a strong, shared genetic influence between ADHD and school performance.