Risperidone in Children and Adolescents with severe disruptive behavior problems.

1. Age between 5 and 17 years 2 months;

2. Body weight > 15 kg;

3. DSM-IV TR diagnosis of Autistic Spectrum Disorder (Autistic disorder or Asperger syndrome or PDDNOS (established by clinical assessment, corroborated by algorithm cutoff scores on the Autism Diagnostic Interview);

4. Inpatients or outpatients;

5. Medication-free for at least two weeks for all psychotropic medications (four weeks for fluoxetine or depot neuroleptics). In the case of ADHD-comorbidity ritalin can be continued, provided that no changes in dose during the study will occur;

6. Anticonvulsants used for the treatment of a seizure disorder will be permitted if the dosage has been stable for 4 weeks and the patient is seizure free for at least 6months;

7. Clinical Global Impression (CGI) severity score of at least 4; and a score of 18 or greater on the Irritability Scale of the Aberrant Behavior Checklist;

8. A mental age of at least 18 months as measured by the age –appropriate form of the Wechsler Intelligence test (whenever possible) or by the revised Leiter or by the Mullen.

1. Females with a positive Beta HCG pregnancy test;

2. Evidence of hypersensitivity to risperidone (defined as allergic response [e.g., skin rash] or potentially serious adverse effect [e.g., significant tachycardia];

3. Past history of neuroleptic malignant syndrome;

4. DSM-IV TR diagnosis of a Pervasive Developmental Disorder other than Autistic Disorder, PDD-NOS, Asperger’s Disorder (e.g., Rett’s Disorder, Childhood Disintegrative Disorder), schizophrenia, another psychotic disorder, substance abuse;

5. A significant medical condition such as heart disease, hypertension, liver or renal failure, pulmonary disease, or unstable seizure disorder identified by history, physical examination or laboratory tests.