Latent class subtyping of attention-deficit/hyperactivity disorder and comorbid conditions.

Objective: Genetic studies of attention-deficit/hyperactivity disorder (ADHD) generally use discrete DSM-IV subtypes to define diagnostic status. To improve correspondence between phenotypic variance and putative susceptibility genes, multivariate classification methods such as latent class analysis (LCA) have been proposed. The aim of this study was to perform LCA in a sample of 1,010 individuals from a nationwide recruitment of unilineal nuclear families with at least one child with ADHD and another child either affected or clearly unaffected.

Cytogenetic abnormalities in attention-deficit/hyperactivity disorder.

Objective: To systematically assess the prevalence of fragile X syndrome, velocardiofacial syndrome, and other cytogenetic abnormalities in a group of children with attention-defict/hyperactivity disorder (ADHD).

Method: Blood samples were obtained from 100 children (64 boys) with combined type ADHD and normal intelligence and analyzed for the presence of fragile X mutation expansions, the 22q11.2 microdeletion associated with velocardiofacial syndrome, and cytogenetic abnormalities that would be detected with high resolution chromosomal banding.