Autism is a complex biological disorder that generally lasts throughout a person’s life. It starts before age three and causes delays or problems with many different ways in which a person develops or grows. Some people with autism become very aggressive and can hurt others or themselves. This study will test the hypothesis that aggressive autistic adolescents will show a significantly greater response to valproate maintained at blood levels of 75-100 mcg/ml than to placebo. The study will also assess the safety of valproate in autistic adolescents. This represents the first double-blind study of valproate in mentally retarded/developmentally delayed populations.

Participants in this study will undergo DSM-IV evaluation, the Autism Diagnostic Interview-Revised and Autism Diagnostic Observation Schedule, and baseline blood tests. After baseline screening, all participants will be given a placebo for 1 week. Participants will then be randomized to receive either valproate or placebo for 8 weeks. Dosage adjustment according to blood levels drawn at the end of weeks 2 and 4 will be arranged with parents by a child psychiatrist without breaking the blind. The Aberrant Behavior Check-list-Community (ABC-C) irritability subscale will be the primary measure; the Overt Aggression Scale (OAS), ABC-C hyperactivity subscale, Clinical Global Impressions (CGI) problem severity, Self-Injurious Behavior Questionnaire (SIB-Q), and a valproate side effects checklist will be secondary measures.