A comparison of medications for severe mental illness shows that an old drug works just as well as new ones for teenagers, plus it doesn't cause the weight gain that has worried patients, parents and doctors, researchers at the University of North Carolina at Chapel Hill report today.

The study, the first to compare the two generations of schizophrenia drugs, could change the way doctors prescribe treatments for teens. The powerful new medications are increasingly prescribed for a variety of disorders, including aggression, hyperactivity, depression and autism.

A national study published in 2006 found that between 1993 and 2002, there was a sixfold increase in the number of doctor visits that resulted in young people getting prescriptions for antipsychotic medications.

And overwhelmingly, teenagers are prescribed the new drugs, which include Risperdal, Zyprexa, Seroquel, Geodon and Abilify.

Few of the drugs have been specifically approved by the Food and Drug Administration for children. But they are widely prescribed because doctors have perceived them as generally safe.

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