Changes in heritability across increasing levels of behavior problems in young twins

Area of Science:

• Behavioral Genetics
• Developmental Psychology
• Psychopathology

Background:

• Childhood behavior problems, including internalizing and externalizing behaviors, are common and can have long-term impacts.
• Understanding the interplay of genetic and environmental factors in the development of these behaviors is crucial for effective interventions.

Purpose of the Study:

• To investigate how heritability (h2) and common environment (c2) influence parent-reported internalizing and externalizing behavior problems.
• To examine if these genetic and environmental influences change with increasing severity of behavior problems across different age groups.

Main Methods:

• Utilized data from 526 identical and 389 fraternal same-sexed twin pairs across five national birth cohorts (ages 5-15).
• Employed multiple regression models to analyze heritability (h2) and common environment (c2) as a function of proband scores.
• Assessed behavior problems using parent-reported Child Behavior Checklist data.

Main Results:

• Both internalizing and externalizing behaviors demonstrated significant heritability.
• Externalizing behavior heritability (h2) increased, and common environmental influence (c2) decreased with greater problem severity, irrespective of age or sex.
• For internalizing behaviors, h2 increased and c2 decreased with severity in younger children (5-9 years).
• Logarithmic transformation of scores reduced heritability and increased environmental influence, particularly for externalizing behaviors, rendering severity-related changes nonsignificant.

Conclusions:

• Heritability of childhood behavior problems is not static; it increases with problem severity, suggesting a greater role for genetic predisposition in more pronounced behaviors.
• Shared environmental influences appear to decrease as behavior problems become more severe.
• The observed changes in heritability with severity are robust for raw scores but diminish with data transformation, highlighting the importance of measurement choices.