Genetic and environmental factors discrimination in attention deficit hyperactivity disorder

Introduction and objective. In order to elucidate the genetic and environmental components involved in the susceptibility to develop attention deficit hyperactivity disorder (ADHD), a complex segregation analysis on nuclear families (n = 53) ascertained from affected probands belonging to Medellin, in the Antioquian State, Colombia, was performed. Methods and results. Models of cohort effect (non-inheritance), multifactorial, recessive major gene, non-major gene component and non-transmission of major gene were rejected. Contrarily, dominant and codominant major gene models anti non-multifactorial component could not be rejected. Thus, the better model fitting the data was that of the major gene (dominant/codominant). This major gene explains more than 99,99% of the the ADHD phenotypic variance (value of heritability in the mixed model equal to 0.007%), which permit to assume a low aport of the environmental component to the phenotype ADHD. Gene frequency of the major gene was 3% in the general population of Antioquia and its penetrance was closed to 30%. Conclusion. Some cautions and aspects related to the bias of the interview and diagnosis of the parents are discussed.