Codevelopment of ADHD and externalizing behavior from childhood to adulthood.

Area of Science:

• Developmental Psychology
• Psychopathology
• Behavioral Genetics

Background:

• Attention-Deficit/Hyperactivity Disorder (ADHD) frequently co-occurs with externalizing disorders.
• Understanding the developmental pathways of these co-occurring conditions is crucial but limited.

Purpose of the Study:

• To investigate the codevelopment of ADHD and externalizing behaviors from childhood to early adulthood.
• To examine the directionality and stability of these traits over time.

Main Methods:

• Utilized a Swedish birth cohort of 2600 twins assessed from childhood (8-9 years) to early adulthood (19-20 years).
• Employed parent and twin ratings of ADHD-like and externalizing traits using the Child Behavior Checklist.
• Analyzed cross-lagged effects and decomposed trait covariation into stable and innovative genetic and environmental sources.

Main Results:

• Externalizing traits in middle childhood predicted ADHD-like traits in early adolescence.
• ADHD-like traits in late adolescence predicted externalizing traits in early adulthood.
• Trait correlation increased over time, with substantial contributions from innovative genetic and environmental factors.

Conclusions:

• Challenges the notion that ADHD always precedes externalizing behaviors, highlighting developmental changes in etiology.
• Emphasizes the role of both novel genetic and environmental factors in the comorbidity across development.
• Recommends complex developmental models for understanding ADHD and externalizing behavior comorbidity.