This is true for understanding the genetics of ADHD.
Here are a few selected recent twin studies in ADHD that I think are important and noteworthy.
Readers can access the abstract and in some cases the free full-text manuscript by clicking on the title.
Shared Features of ADHD and Autism
This study featured results of an analysis of over 17000 adult twins from Sweden. The authors examined scores on two features of autism (social/communication and repetitive/restricted behavior) and scores on two features of ADHD (inattention and hyperactivity/impulsivity). The authors found support for a genetic overlap between the repetitive/restrictive autism dimension with both the attention and hyperactivity dimensions of ADHD.
Cognitive Impairments, Reading Difficulty and ADHD
Using a sample of twins between ages 7 and 10 the authors found a link between ADHD inattention scores and three measures of cognition (reaction time variability, verbal short-term memory and working memory. These associations accounted for a significant portion of the reading difficulties in children with ADHD.
ADHD, Autism Traits and Substance Use and Misuse
3080 adult Australian twins participated in a study of the overlap between ADHD, autism traits and substance use. Both ADHD symptoms and autism traits were linked to smoking and cannabis use. Autism traits were linked to lower frequency of drinking to intoxication but higher rates of alcohol dependence once drinking was initiated.
EEG Theta Activity, Reaction Time and ADHD
EEG abnormalities have been noted in ADHD. In this twin study, twins between 12 and 15 years of age completed EEG frontal theta phase assessments, reaction time variability and ADHD symptomatology. The authors found evidence to support a genetic link between frontal EEG theta, reaction time variability and ADHD status.
ADHD, Homework Behavior and Reading Comprehension
This study analyzed data from the Florida Twin Project on Behavior and Environment. Overlapping genetic contributions for found for ADHD symptoms, homework behavior and reading comprehension. Additionally, some shared environmental influences contributed to the association between homework behavior and reading comprehension. This study supports both genetic and environmental influences on the link between ADHD and reading performance.
The findings from these recent twin studies show the importance of genetic influences in ADHD and highlight the key overlap with autism, cognitive function and academic achievement.
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