Is ADHD biological or environmental?

John Hopton for redOrbit.com – @Johnfinitum
A 2012 article in Psychology Today discussed the fact that French children are treated very differently for ADHD (Attention-Deficit/Hyperactivity Disorder) compared to American children, and are diagnosed far less often. The suggestion was that American doctors could be wrong in treating ADHD as biological, and prescribing drugs, and rather should take the French approach of considering it environmental and adjusting environmental factors accordingly.
But recently, a major investigation into collated twin studies over 50 years looked at the balance of “nature v. nurture” – biological factors vs. environmental – in a huge number of human traits, including ADHD. The findings largely contradicted the Psychology Today article.
The Psychology Today writer was Marilyn Wedge Ph.D., author of A Disease Called Childhood: Why ADHD Became an American Epidemic.
Wedge said that in the United States, at least 9 percent of school-aged children have been diagnosed with ADHD, and are taking pharmaceutical medications. Whereas in France, the percentage of children diagnosed and medicated for ADHD is less than 0.5 percent.
She wrote: “Is ADHD a biological-neurological disorder? Surprisingly, the answer to this question depends on whether you live in France or in the U.S. In the United States, child psychiatrists consider ADHD to be a biological disorder with biological causes. The preferred treatment is also biological—psycho stimulant medications such as Ritalin and Adderall.”
“French child psychiatrists, on the other hand, view ADHD as a medical condition that has psycho-social and situational causes. Instead of treating children’s focusing and behavioral problems with drugs, French doctors prefer to look for the underlying issue that is causing the child distress—not in the child’s brain but in the child’s social context.”
The verdict
Beben Benyamin, of the University of Queensland, Australia, and lead author of the nature or nurture study, told RedOrbit that:
“We used the International Statistical Classification of Diseases and Health Related Problems (ICD-10) to classify diseases. Within ICD-10 classification, ADHD was listed as Hyperkinetic Disorders. (You can check the heritability (h2_all) of this disorder in the interactive website that we provided here under ICF/ICD10 sub chapter):”
“We found that the average heritability estimate for hyperkinetic disorders from all twin studies is 68 percent. This means that about 68 percent of the individual difference in susceptibility to ADHD was due to genetic factors.”
It should be noted that the root causes of ADHD and the treatment of it are not necessarily the exact same question. While it makes sense that doctors who believe it is more due to biology would treat it as such, it is also fair to say that additionally changing diet or social situations could reduce the negative impact of ADHD, regardless of cause. Especially given that the study found a reasonable percentage (32) of influence to be environmental.
Nevertheless, if the large and comprehensive recent twin study is to be believed, considering ADHD to be predominantly due to biology is correct.
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