Associations of MAOA-VNTR or 5HTT-LPR alleles with attention-deficit hyperactivity disorder symptoms are moderated by platelet monoamine oxidase B activity

Psychiatr Genet. 2012 Feb;22(1):42-5. doi: 10.1097/YPG.0b013e328347c1ab.


The monoamine systems have been suggested to play a role in the biological basis of attention-deficit hyperactivity disorder (ADHD) symptoms. Thus, polymorphisms, for example, in the monoamine oxidase A (MAOA) and the serotonin transporter (5HTT) genes have been associated with ADHD-like phenotypes. Furthermore, platelet monoamine oxidase B (MAOB) activity has frequently been linked to impulsiveness-related traits. In this study, we have studied ADHD symptoms with regard to the combination of platelet MAOB activity and MAOA-variable number of tandem repeats (VNTR) or 5HTT-LPR genotype. The study group consisted of 156 adolescent twin pairs, that is, 312 individuals, who participated in a previous study. ADHD symptoms were scored with a structured clinical interview of both the twins and a parent using Kiddie Schedule for Affective Disorders and Schizophrenia for School-Age Children-Present and Lifetime Version. The presence of a short 5HTT-LPR or short MAOA-VNTR allele, in combination with high levels of platelet MAOB enzyme activity was associated with higher scores of ADHD-like problems (P<0.001 and 0.01, respectively). This re-examination of ADHD scores in a nonclinical sample suggests that effects of MAOA-VNTR and 5HTT-LPR are moderated by platelet MAOB activity.

Publication types

  • Research Support, Non-U.S. Gov't
  • Twin Study

MeSH terms

  • Adolescent
  • Alleles*
  • Attention Deficit Disorder with Hyperactivity / genetics*
  • Blood Platelets / enzymology*
  • Female
  • Genetic Association Studies
  • Genetic Predisposition to Disease
  • Humans
  • Male
  • Minisatellite Repeats / genetics*
  • Monoamine Oxidase / genetics*
  • Monoamine Oxidase / metabolism*
  • Serotonin Plasma Membrane Transport Proteins / genetics*


  • SLC6A4 protein, human
  • Serotonin Plasma Membrane Transport Proteins
  • Monoamine Oxidase