ADHD and Head Injury Link Examined
Recent evidence disputes the theory that head injury early in life increases the risk of developing attention deficit/hyperactivity disorder (ADHD).
There is a well-established link between ADHD and traumatic head injury, with some experts suggesting that brain injury in school-age children causes ADHD. But this has not been conclusively confirmed, and it may be that children with ADHD are more likely to sustain a head injury due to a pattern of riskier behavior.
Writing on the website of the British Medical Journal, Professor Heather Keenan of the University of Utah and her team state that “the direction of the relation between ADHD and head injury has been difficult to elucidate,” but “understanding the nature of the association is important.”
The team explored the link using a database of 62,088 children registered with the National Health Service in the UK. Of the children, 2,782 (4.5 percent) had sustained a head injury before the age of two years. A further 1,116 (1.8 percent) of the children had sustained a burn or scald injury. Among all of the children, 934 (1.5 percent) were diagnosed with ADHD between the ages of two and 10 years.
Analysis showed that the rate of ADHD diagnosis before age 10 was similar in both injury groups, but this rate was significantly higher — approximately double — that of the uninjured children. Previously-injured children made up 6.3 percent of the total number, but 11.3 percent of those with ADHD.
As found in previous studies, ADHD was more common among boys, children who were born prematurely, and those in “more deprived” circumstances as measured by a reliable index. The research also indicates that children with ADHD may be more vulnerable to serious concussion after a brain injury, placing them “at high risk for poor outcomes from subsequent head injuries.”
In an editorial alongside the research report, specialist doctors take up this point, saying that monitoring children with early injuries could reduce later risk of ADHD. Dr. Morris Zwi of South West London and St. George’s NHS Mental Health Trust, London, UK, and Dr. Philip Clamp, a general practitioner in Bromsgrove, Worcestershire, UK, state that both the cause and treatment of ADHD remain uncertain, and have provoked considerable debate.
Concern has been expressed internationally about the increased prescribing of drugs to treat ADHD in children, they write, and international estimates of prevalence vary considerably.