Brain EEG and the Genetics of ADHD

Twin studies in ADHD demonstrate a significant genetic contribution to the disorder.

Linking this genetic influence to specific biomarkers may provide a better understanding of the pathophysiology of ADHD.

Grainne McLoughlin and colleagues at the University of California San Diego and King's College London recently published a twin study of brain EEG and the genetics of ADHD.

In their study 67 twin pairs (34 monozygotic and 33 dizygotic) between the ages of 12 and 15 years completed tasks measuring brain frontocentral EEG theta patterns and reaction time.

Brain EEG frontocentral theta EEG levels increase under tasks requiring cognitive control, reaction time and handling reaction under conflict.

The authors were able to identify a specific type of EEG response in twins with ADHD compared to twins without the disorder. 

• Twins without ADHD showed changes in reaction time variability (RTV) and EEG theta performance with an attention and reaction task. 
• Twins with ADHD showed no change in these measures with the same attention and reaction task.

Of note, the authors were able to link this specific RTV and theta response to genetic features contributing to ADHD.

The authors note in their conclusion:

"This is the first finding that confirms the genetic link between frontal midline EEG activity and ADHD, as previously suggested by family studies."

This is an important finding and has significant implications in:

• Furthering understanding an EEG evoked response that may assist in the diagnosis of the ADHD phenotype
• Provide a biomarker for future family, twin and genome-wide genetic studies of ADHD
• Be helpful in teasing out environmental from genetic factors in ADHD

Readers with more interest in this study can access the free full-text manuscript by clicking on the PMID link in the citation below.

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McLoughlin G, Palmer JA, Rijsdijk F, & Makeig S (2014). Genetic overlap between evoked frontocentral theta-band phase variability, reaction time variability, and attention-deficit/hyperactivity disorder symptoms in a twin study. Biological psychiatry, 75 (3), 238-47 PMID: 24001472