ADHD Clinical Update, August 11, 2011

The latest in clinical research on the diagnosis and treatment of ADHD.

Attention Deficit and Hyperactivity Disorder (ADHD) symptoms may put children at increased risk for reading problems and vice versa, according to the results of a recent study. Moreover, enduring genetic mechanisms appear to be important in the association of ADHD symptoms and reading over time.

“ADHD and reading disability commonly co-occur because of shared genetic risk factors. However, the stability and change of these genetic influences and the predictive relationships underlying this association longitudinally remain unclear,” wrote the researchers, who were headed by Corina U. Greven, a doctoral student at the Social, Genetic, and Developmental Psychiatry Centre at King’s College London in the United Kingdom. Their research was published in the Journal of Child Psychology and Psychiatry.

For the study, ADHD symptoms and reading were assessed as continuous dimensions in a UK general population sample of approximately 7,000 twin pairs. Parent ratings of ADHD symptoms and teacher ratings of reading were obtained at two ages: middle childhood (ages 7-8 years) and early adolescence (ages 11-12). Cross-lagged quantitative genetic analyses were applied.

The results showed that ADHD symptoms and reading significantly predicted each other over time. “However, ADHD symptoms were a significantly stronger predictor of reading than vice versa. Inattentive and hyperactive-impulsive symptoms of ADHD both contributed to the prediction of reading, but inattentiveness was a significantly stronger predictor,” the researchers wrote in the study abstract.

“Furthermore, ADHD symptoms and reading were highly heritable, and their association was primarily attributable to shared genetic influences. Despite notable genetic innovation for each trait, genetic factors involved in the association of ADHD  symptoms and reading over time were highly stable.”

Growth Dysregulation and ADHD: An Epidemiologic Study of Children in France

Some literature has suggested that attention deficit hyperactivity disorder (ADHD) may be associated with dysregulated growth, but this work primarily used clinically referred samples, so it is difficult to interpret.

Recent data do not cast doubt on the well-documented association of stimulant treatment with delays in growth, but they do provide some support for the idea that, in the absence of medication exposure, ADHD is associated with dysregulated growth, according to the results of a study published in the Journal of Attention Disorders.

French researchers, headed by Steven V. Farone, PhD, of the Department of Psychiatry and Behavioral Sciences at the SUNY Upstate Medical Center in Syracuse, N.Y., selected 18 million telephone numbers in France and randomly called 7,912. Among 4,186 eligible families, 1,012 were recruited. The goal was for the final distribution of the sample to match the demographic background of the French population. A telephone interview was administered to all families to diagnose ADHD and assess other psychopathology and functioning variables, according to the study, which was published in the Journal of Attention Disorders.

“In young children, medication-naïve ADHD was associated with being taller, t(515)=26.3, P<.001 and heavier, t(518)=1.8, P=.03,” the researchers wrote. “In contrast, for older children, medication-naïve ADHD participants were shorter and weighed less. These results were stronger for weight than height.”

SourcesA Longitudinal Twin Study on the Association between ADHD Symptoms and Reading [Journal of Child Psychology and Psychiatry]Growth Dysregulation and ADHD: An Epidemiologic Study of Children in France [Journal of Attention Disorders]