ADHD Across Generations

A recent study, published in the Journal of Child Psychology and Psychiatry, confirmed that the recurrence risk of ADHD from generation to generation may be influenced by gender. It also indicated the presence of other psychiatric disorders in parents may also increase the risk of ADHD in offspring.

Genes and ADHD

ADHD has long been known to be a heritable neurodevelopmental disorder. At least one-third of all fathers who had ADHD in their youth have children with the condition. What’s more, the majority of identical twins share the ADHD trait.

Recent research indicates that changes in dozens of genes are associated with ADHD. Many gene variations are thought to affect the risk of developing ADHD. Many of the gene variations have only a small effect, and most people with ADHD are thought to have numerous associated gene variations. These variations combine with environmental risk factors to determine an individual’s overall risk of developing ADHD. It is still not yet clear how genetic and environmental factors influence each other to contribute to ADHD.

The Risk of Inheriting ADHD

Two interesting aspects of this research were the size of the population sample, as well as a direct focus on the recurrence risk of ADHD from mothers and fathers to offspring. The study used a large combination of nationwide population-based registries of more than 2.6 million adults, aged 15-45 years old, with information about ADHD in offspring and associated parental psychiatric disorders.

Findings from the study showed that:

The overall prevalence of ADHD in offspring to affected parents was very high (17.8-24.2%)
Prevalence was higher in sons at 21.9-29.7% than daughters
When both parents had ADHD, it was 41.5% for sons and 25.1% for daughters
There is a stronger recurrence risk of ADHD from mothers than from fathers, and in both cases, strongest to daughters.
Prevalence rates of ADHD were also higher in offspring to parents with certain other psychiatric disorders than in offspring of unaffected parents, but far lower than when parents had ADHD.
Certain disorders in parents also confer increased risk of offspring ADHD, with parental sex-specific risk patterns, but with no differences between daughters and sons.

Toward a Better Understanding of Risk Among Clinicians

Berit Skretting Solberg, MD, PhD who headed up the research project, expressed the hope that clinicians could use the findings of her group to become more aware of the High prevalence of ADHD in children of parents with the condition.

“We want clinicians working in child and adolescent as well as adult psychiatry to be aware of the very high prevalence of ADHD in sons of affected parents and evaluate possible diagnostic bias and underdiagnosing of daughters. Further, an awareness of possible ADHD in offspring if parents have other psychiatric disorders is warranted,” she said. “We believe that early recognition is important to prevent the risk of increased psychiatric comorbidity associated with ADHD for both males and females. However, further research is needed to understand underlying environmental and genetic causes of these observed sex differences and prevalence of ADHD in affected families.”