Behavioral problems of autistic children can be reduced through medication and a parental training program, U.S. researchers say.

The 24-week study involved 124 children ages 4-13 with autism, Asperger's or related disorders at Yale University.

The research, conducted by the National Institute of Mental Health Research Units on Pediatric Psychopharmacology Autism Network, found anti-psychotic medication risperidone, or Risperdal, reduced behavioral problems as tantrums, aggression and self-injury in children with autism.

However, most children's symptoms returned when the medication was discontinued after six months.

Researchers at Yale University, Ohio State University and Indiana University tested the benefits of medication alone compared with medication plus a parent training program that actively involves parents in managing their children's severely disruptive and non-compliant behaviors.

In a series of 14 sessions over six months, parents were taught to reduce their children's challenging behavior and to enhance daily living skills.

The study, to be published in the December issue of the Journal of the American Academy of Child and Adolescent Psychiatry, found although both groups improved over the six-month trial, the group receiving combination therapy showed greater reduction in disruptive behavior, tantrums and aggression compared with the group receiving medication only.