Some doctors are taking a look at how many children are taking anti-psychotic medicines, and the effects of treating conditions like autism and hyperactivity.

About six times as many American children are prescribed medicines as are those in the United Kingdom, but experts say usage is increasing in both countries.

The study appearing in the May edition of the journal Pediatrics also looks at side effects, like weight gain, heart trouble and nervous-system problems.

One pediatrician said the study shows drugs are being used "without full understanding about the risks."

There are big differences that could help explain the vastly higher U.S. rate.

Another recent report has suggested that the U.K.'s universal health care system limits prescribing practices there.

It also said direct-to-consumer ads are more common in the U.S.