THE NUMBER of children being treated with anti-psychotic drugs has risen sharply, according to a new study.

Research by academics at the University of London's Pharmacy School found that in 1992 595 children in Britain were prescribed anti-psychotics at a rate of less than four per 10,000 children.

But by 2005, that figure had risen to 2,917 children at a rate of seven per 10,000, the study's lead author Fariz Rani found.

It also discovered that most of those drugs prescribed were not officially approved for children, with the most commonly prescribed ones being those to treat autism and hyperactivity.

Side effects including weight gain and heart trouble have been reported in autistic or hyperactive children treated with anti-psychotic drugs and there is little long-term evidence that the drugs are safe, the report's authors claimed.

They said: "This highlights the need for long-term safety investigations and ongoing clinical monitoring, particularly if the prescribing rate of these medicines continues to rise."

One of the most commonly used anti-psychotics in the UK is Risperdal, a schizophrenia drug that is sometimes used to treat irritability and aggression in autism. Its side effects include drowsiness and weight gain.

The figures still put the UK well behind the US in the numbers of children being treated with the drugs.

An earlier US study found nearly 45 American children out of 10,000 used the drugs in 2001 up from more than 23 per 10,000 in 1996.

The new study, based on the health records of more than 16,000 children, is the first large examination of the use of these drugs in British children and will be published today in the May edition of the journal Paediatrics.