ADHD News & Research

Genetics May Determine If ADHD Symptoms Improve or Worsen

A new study finds that genetics, more than treatment, may be the driving force behind ADHD symptoms as a child grows.

May 13, 2015

Wondering if your child will ever “grow out” of her ADHD? The answer may come down to genes. A new study of twins suggests that symptom improvement is largely based on genetics — perhaps more so than treatment efforts by parent and child.

The study, conducted by the University College London, examined nearly 8,400 pairs of twins with ADHD born in the United Kingdom between 1994 and 1996. Their parents rated them (using the Conners’ Parent Rating Scale — Revised) on several classic ADHD symptoms, including hyperactivity, impulsivity, and inattention. The children were evaluated several times throughout their childhood and adolescence, starting at age eight and continuing until age 16.

At age eight, the average hyperactivity score was 6.0, while the average inattention score was 5.8. By age 16, hyperactivity had decreased dramatically, to an average of 2.9, while inattention decreased only slightly, to an average of 4.9. This supports anecdotal evidence from many ADHD adults, who claim that while their hyperactivity didn’t last significantly into their adulthood, symptoms of inattention continue to create challenges for them in day-to-day life.

By examining the twins’ genetic patterns, and comparing them to the severity of their symptoms, researchers found that the persistence of hyperactivity was mostly dictated by a combination of two or more genes. Inattention, on the other hand, was dictated by one powerful, dominant gene. These genes are mostly separate from the ones that determined a baseline severity of symptoms when the children were first diagnosed, but can be used to predict how symptoms will decrease — or increase — over time.

The study’s authors hope that, in the future, genetic tests will be available to help parents understand the lifelong impact of their child’s ADHD — which will change the way doctors diagnose and treat the condition. A dramatic increase in symptoms over time, they write, “might represent a marker of vulnerability reflecting genetic liability, and warrant closer follow-up.”

It also raises the question, researchers said, of the need to inform patients about a higher risk of persistent ADHD, based on their genetics and familial history.