Genetics of attention-deficit hyperactivity disorder (ADHD)
Sally I Sharp1, Andrew McQuillin, Hugh M D Gurling
1Molecular Psychiatry Laboratory, Research Department of Mental Health Sciences, Windeyer Institute of Medical Sciences, University College London Medical School, 46 Cleveland Street, London W1T 4JF, UK.
Neuropharmacology
|September 1, 2009
Summary
Genetic studies reveal attention-deficit hyperactivity disorder (ADHD) is highly heritable, with dopamine transporter gene (DAT1) variations linked to specific ADHD subtypes. This highlights significant genetic overlap between ADHD and bipolar disorder.
Area of Science:
- Psychiatric Genetics
- Neurodevelopmental Disorders
Background:
- Attention-deficit hyperactivity disorder (ADHD) is a complex neurodevelopmental disorder with significant genetic underpinnings.
- ADHD frequently co-occurs with other psychiatric conditions, including conduct disorder, substance abuse, and affective disorders, suggesting shared genetic etiologies.
- Previous research indicates substantial genetic heritability for ADHD, with environmental factors playing a minimal role.
Purpose of the Study:
- To investigate the genetic basis of ADHD, focusing on its heterogeneity and overlap with other disorders.
- To identify specific genes and genetic markers associated with ADHD subtypes and comorbid conditions.
Main Methods:
- Review of twin and family studies to assess heritability.
- Analysis of linkage and association studies implicating specific genes, such as the dopamine transporter gene (DAT1) and DRD4 dopamine receptor gene.
- Examination of preliminary genome-wide association and copy number variant data.
Main Results:
- The dopamine transporter gene (DAT1) is strongly implicated in ADHD, with specific DAT1 markers associated with the non-conduct disordered subgroup, suggesting predictive value for clinical heterogeneity.
- The DRD4 dopamine receptor gene is the second most replicated susceptibility gene for ADHD.
- Emerging evidence indicates genetic overlap between genes contributing to ADHD subtypes and those involved in bipolar disorder and autism.
Conclusions:
- Understanding ADHD genetics requires acknowledging significant heterogeneity, with different genes influencing different individuals and families.
- Genetic factors underlying ADHD, particularly specific subtypes, show considerable overlap with those of affective disorders like bipolar disorder.
- Further research, including genome-wide studies, is crucial to fully elucidate the complex genetic architecture of ADHD and its relationship with other neurodevelopmental and psychiatric conditions.
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