Objective: To assess the genetic and environmental influences on attention problems in a general population twin sample and to investigate whether there are changes in the relative genetic influence on attention problems with increasing severity.
Method: Parental ratings of the Child Behavior Checklist were collected from five Norwegian national cohorts of same-sex twins. The sample comprises 526 identical and 389 fraternal pairs.
Results: Considerable genetic influence on attention problems was found for both sexes and across age groups (aged 5 to 9 years and 12 to 15 years). A two-parameter model with additive genetic influence and nonshared environment showed a good fit, with heritability ranging from .73 in boys aged 5 to 9 years, to .76 in girls aged 5 to 9 years. There was no change in the relative genetic influence across severity after accounting for the influence of cerebral palsy, epilepsy, and low birth weight.
Conclusion: The results indicate a substantial genetic influence on attention problems across sex, age, and severity.