The use of these drugs to treat ADHD has not been approved by the US Food and Drug Administration, and is known as an "atypical" use, the researchers explained.
But their study found that antipsychotics were used to treat nearly one-third of foster care youth aged 2 to 17 who had been diagnosed with ADHD. The most common types of antipsychotics used were risperidone, aripiprazole and quetiapine.
The study looked at administrative data on more than 260 000 youths aged 2 to 17, enrolled in one state's Medicaid program in 2006, to determine the average number of days of atypical antipsychotic use in kids.
Researchers also looked specifically at a subgroup of kids with ADHD who were not diagnosed with any other mental health conditions.
The findings by researcher Julie Magno Zito, at the University of Maryland at Baltimore, and colleagues were published online recently in the Journal of Child and Adolescent Psychopharmacology.
"This study adds critical hard data to our understanding of a persistent and unacceptable trend in paediatric psychiatry," Dr Harold Koplewicz, journal editor-in-chief and president of the Child Mind Institute in New York City, said in a journal news release.
"Our poorest, most vulnerable children, lacking access to evidence-based care, are receiving potentially harmful treatment with little oversight.
The highlight of [the] paper for any reader should be the simple but necessary recommendations for antipsychotic prescribing and monitoring in these populations," he added.
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