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Children between the ages of two and five are being treated with antipsychotics at twice the rate they were ten years ago, according to a study conducted by researchers from Columbia University and published in the journal Health Affairs.

"It is a worrisome trend, partly because very little is known about the short-term, let alone the long-term, safety of these drugs in this age group," researchers Mark Olfson said.

Although a handful of antipsychotics have been approved by the FDA for use in children, they are intended for older children because few if any studies have been conducted into the effectiveness or safety of the drugs in younger children.

Researchers examined prescription data on more than one million children between the ages of two and five. They found that from 1999-2001, approximately one out of every 1,300 children in this age group was being treated with an antipsychotic drug. By 2007, the rate was one in every 630. Among the oldest children (five-year-olds), the rate has always been higher. In 1999-2001, one in every 650 children was receiving an antipsychotic, while in 2007 one in every 329 was.

Although the drugs are intended for the treatment of severe conditions such as schizophrenia and some forms of autism, the study found that they were being used most commonly for hyperactivity, disruptive behavior, and children with mental developmental disabilities.

Olfson noted that antipsychotics should only be used in four- and five-year-olds as an absolute last resort, when no other form of non-drug therapy has been effective. He questioned whether there is ever any justification for giving the drugs to two- or three-year olds. Yet the study found that less than 50 percent of children under the age of six who are on antipsychotics have ever received any mental health services, including therapy or even a health assessment by a mental health professional.

"You don't see the kinds of mental health services you would expect to see if we were dealing with the most profoundly disturbed toddlers," Olfson said.

Few studies have been done into the effects of psychotropic drugs on a child's developing brain.