Association of autism severity with a monoamine oxidase A functional polymorphism

Clin Genet. 2003 Sep;64(3):190-7. doi: 10.1034/j.1399-0004.2003.00115.x.


A functional polymorphism (the upstream variable-number tandem repeat region, or uVNTR) in the monoamine oxidase A (MAOA) promoter region has been reported to be associated with behavioral abnormalities as well as increased serotonergic responsivity. We examined the relation between MAOA-uVNTR alleles and the phenotypic expression of autism in 41 males younger than 12.6 years of age. Children with the low-activity MAOA allele had both lower intelligence quotients (IQ) and more severe autistic behavior than children with the high-activity allele. In follow-up testing of 34 of the males at the 1-year time-point, those with the low-activity allele showed a worsening in IQ but no change in the severity of their autistic behavior. We conclude that functional MAOA-uVNTR alleles may act as a genetic modifier of the severity of autism in males.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Activities of Daily Living
  • Adaptation, Psychological
  • Alleles
  • Autistic Disorder / genetics*
  • Autistic Disorder / psychology
  • Child
  • Child, Preschool
  • Cognition
  • Female
  • Follow-Up Studies
  • Genetics, Behavioral
  • Genotype
  • Humans
  • Intelligence Tests
  • Language Tests
  • Longitudinal Studies
  • Male
  • Minisatellite Repeats*
  • Monoamine Oxidase / genetics*
  • Monoamine Oxidase / physiology
  • Promoter Regions, Genetic / genetics*
  • Psychological Tests
  • Severity of Illness Index
  • Sex Factors


  • Monoamine Oxidase