Analysis of a population-based cohort of twins indicated that genetics significantly influence the developmental course of ADHD symptoms.
To assess environmental and genetic effects on individual differences in inattention and hyperactivity/impulsivity at baseline and during developmental course, Jean-Baptiste Pingault, PhD, of University College of London, and colleagues applied genetically informative growth curve models to a cohort of 8,395 twin pairs who exhibited ADHD symptoms. Data from medical records was collected at ages 8 and 16 years. Study participants were born in England and Wales between 1994 and 1996.
Analysis of latent growth curve models showed a significant linear decrease in the developmental course of hyperactivity/impulsivity symptoms, from a mean score of 6 at age 8 years to 2.9 at age 16 years.
Eighty-one percent of interindividual differences in the linear change of hyperactivity/impulsivity symptoms were due to additive genetic influences (95% CI, 73%-88%). More than half of the genetic variation was specific to the developmental course vs. baseline level of hyperactivity/impulsivity.
Inattention symptoms also experienced a linear decrease, but this was less pronounced than that of hyperactivity/impulsivity symptoms, from a mean score of 5.8 at age 8 years to 4.9 at age 16 years.
Fifty-four percent of variation in the developmental course of inattention symptoms was due to nonadditive genetic influences (95% CI, 8%-76%) and more than half was specific to the developmental course.
“The confirmation of large genetic influences on the developmental course of ADHD symptoms is important for both clinicians and patients,” Pingault and colleagues wrote. “For clinicians, the maintenance or increase in symptoms (a decline being normative in the population) might represent a marker of vulnerability reflecting genetic liability and warrant closer follow-up. It also raises the question of the necessity to inform patients and their relatives about the higher risk of persistence in families of index cases with persistent symptoms.” – by Amanda Oldt
Disclosure: Pingault reports no relevant financial disclosures. Please see the full study for a list of all other authors’ relevant financial disclosures.