An Overview on the Genetics of ADHD

Area of Science:

• Genetics
• Neuroscience
• Psychiatry

Background:

• Attention Deficit Hyperactivity Disorder (ADHD) is a common childhood-onset disorder with familial and heritable components.
• Traditional studies (family, twin, adoption) confirm ADHD's genetic basis.
• Current research explores ADHD phenotype definition, gender differences, continuity, comorbidity, and gene-environment interplay.

Purpose of the Study:

• To review current molecular genetic findings in ADHD.
• To examine the evidence for specific gene associations and their influence on ADHD phenotypes.
• To highlight the importance of gene-environment interactions in ADHD.

Main Methods:

• Review of functional candidate gene association studies, pooled analyses, and meta-analyses.
• Examination of twin studies for phenotype definition, gender differences, continuity, comorbidity, and gene-environment interplay.
• Analysis of linkage studies and consideration of whole-genome association studies.

Main Results:

• Consistent associations found between ADHD and dopamine D4 receptor gene (VNTR) and dopamine D5 receptor gene (microsatellite).
• Evidence suggests the COMT val158/108 met variant influences conduct problems in individuals with ADHD.
• Linkage studies indicate no major genes of moderate effect size; large-scale WGA studies are pending.

Conclusions:

• Investigating gene-phenotype links and gene variant effects on the ADHD phenotype is crucial.
• Gene-environment interplay is increasingly recognized in psychopathology, but causal environmental risk factors for ADHD remain largely unknown.