Gerald J. August

Behavioral and Cognitive Subtypes of ADHD

Attention-deficit hyperactivity symptoms are observed by teachers in 9.2% of a nonreferred elementary school population. Two subtypes of attention-deficit hyperactivity disorder (ADHD), a cognitive form and a behavioral form, are identified. The behavioral subtype includes about 80% of those identified and is characterized by distinct clinical phenomenology of inattention, impulsivity, and hyperactivity. These children can be described on a continuum of severity, with the most severe showing behavioral features indistinguishable from conduct disorder. Children with behavioral subtypes of ADHD do not exhibit the specific skill deficits on neuropsychological tests that are characteristic of reading disabled children. There is a second, less prevalent type of cognitive attention-deficit hyperactivity disorder constituting approximately 20% of ADHD children that includes severe academic underachievement along with inattention, impulsivity, and overactivity. Children with the cognitive subtype exhibit information processing deficits that involve inadequate encoding and retrieval of linguistic information, characteristic of reading disabilities.

Familial Heterogeneity in Infantile Autism.

The incidence of autism and cognitive disability was assessed in the biological siblings of 29 autistic probands subdivided on the basis of IQ. A significant clustering of autism and nonspecific intellectual retardation was found in the siblings of severely retarded autistic probands which was not present in the siblings of our higherfunctioning autistic sample. These findings suggest that there may be etiological differences in autism, depending on the degree of associated mental retardation.

Familial subtypes of childhood hyperactivity.

On the basis of family history data we defined two subtypes of childhood hyperactivity: family history-positive (FH+), in which at least one biological parent of the child had a diagnosis in the antisocial spectrum; and family history-negative (FH-), in which neither parent had such a diagnosis. While children in both subgroups were equally deviant on measures of the core components of childhood hyperactivity (e.g., inattention and reactivity), the FH+ children were also deviant on dimensions of conduct disturbance and had siblings with a high prevalence of conduct disorder. FH- children showed little evidence of conduct disturbance, had more learning and academic problems, and had siblings with attentional and learning disabilities, but not conduct disorder. These findings suggest that the study of family constellations should be a fruitful method for resolving the heterogeneity of the hyperactive child syndrome.

Fenfluramine treatment in infantile autism. Neurochemical, electrophysiological, and behavioral effects

As part of a multi center, collaborative project, response to fenfluramine was assessed in 10 autistic outpatients. After 4 months of treatment, blood serotonin concentrations decreased an average of 60 per cent and returned to pretreatment levels after 2 months on placebo. This reduction was accompanied by a decrease in certain behavioral symptoms, including motor activity, distractibility, and mood disturbances. Baseline evoked potential recordings indicated that autistic patients tended to have a larger amplitude of the P3 component to frequent tones as compared to age-matched controls. A tendency toward “normalization” of the P3 effect was observed during the medication trial and during the final placebo period. Treatment response was not related to initial serotonin levels, and no major clinical side effects were associated with fenfluramine.

Familial autism and the fragile-X chromosome

This report presents two male siblings in whom the diagnosis of infantile autism was found in association with a fragile site on the X chromosome. In addition to their marked autistic characteristics, formal examinations indicated that both boys were severely mentally retarded and had several physical features commonly observed in association with the fragile-X syndrome. The mother of these two siblings also gave birth to identical twin boys, who were developmentally delayed and showed several autistic features prior to their untimely death in a house fire. The possible role of the fragile-X chromosome as an etiological factor in families where there is a clustering of autism and related developmental disturbances is discussed.