Jim Stevenson

Evidence for a genetic etiology in hyperactivity in children.

There has been considerable controversy over the nosology of hyperactivity and attention deficit hyperactivity disorder (ADHD). There have been suggestions that genetic influences may play a role in the origins of individual differences on this dimension or dimensions of behavior and that an understanding of the significance of genetic factors might help to clarify the classification of these disorders. Multiple regression is used to analyze data from a sample of 91 pairs of identical twins and 105 pairs of same sex fraternal twins. The heritability of extreme group membership (h2g=0.75) was significant for activity rated by the mother. The heritability for one of the measures of attention deficit was also significant (h2g=0.76). The results are consistent with a significant genetic contribution to individual differences in activity levels and attention abilities.

Behavior, language, and development in three-year-old children

An epidemiological study of 3-year-old children showed there to be a marked association between behavior problems and language delay. Behavior problems were present in 14% of a random sample of 705 children, whereas 59% of 22 children with language delay had such problems. Data obtained from a battery of developmental tests were analyzed to examine the differences between children with behavior problems, matched controls, and children with language delay. It was found that children with behavior problems scored significantly lower on these tests, particularly those concerned with language. There were no significant differences in test scores between children with language delay only and those with combined behavior problems and language delay.

Behavioral Deviance in 13-Year-Old Twins: An Item Analysis

Abstract A genetic study of behavioral deviance in 285 pairs of 13-year-old twins is described. Parents and teachers completed standardized questionnaires on the total sample. Concordance rates for monozygotic and dizygotic twins with respect to individual items of behavior, as well as antisocial and neurotic subscale scores, were calculated to produce an estimate of the genetic contribution to etiology of deviance. It is concluded that genetic influences are greatest for items relating to overactivity, inattention, and lack of concentration but are present to a less certain degree for a range of neurotic, antisocial, and psychosomatic behavior items.

Which Aspects of Processing Text Mediate Genetic Effects

Genetic influences on reading are investigated in a sample of 285, 13 year old twins. Using a multiple regression procedure, the heritability of disability (hg2) for Reading Recognition was found to be non-significant. However the hg2 for spelling disability was found to be 0.58 (P<0.05), after controlling for individual differences in IQ. The twins in this study were an unselected sample from the general population. Therefore it was possible to estimate hg2 for differing degrees of severity of disability. These analyses showed that for spelling but not for Reading Recognition or Reading Composite, there were substantial genetic contributions to all levels of disability. For indices of Orthographic Coding there were no significant values of hg2. In contrast measures of Phonological Coding and Homophone Recognition have consistently high values of hg2. More detailed analyses suggested that there were possibly two independent aspects of phonological ability, each influenced by genetic factors.

PREDICTIVE VALUE OF SPEECH AND LANGUAGE SCREENING

In this paper an attempt will be made to reach some conclusions about the natural history of language delays detected during the preschool period. The main concern will be to draw some common links between the findings from three recently published studies of the later developmental outcome of language delays identified in the general population (Fundudis et a/. 1979, Richman er al. 1982, Silva et al. 1983). These studies

Double-Blind Comparison of Clozapine with Chlorpromazine in Acute Schizophrenic Illness*

Double Blind comparative trial of a new dibenzodiazepine derivative Clozapine (Leponex) with Chlorpromazine was conducted in the treatment of acute schizophrenic illness over a 6 week period. Factor Analysis of ratings in 9 matched pairs indicates that Clozapine, at 300 mg. per day, is comparable in efficacy to Chlorpromazine in all factors except “Irritability” for which Clozapine appears to be superior. Illness severity and Global Change ratings in all patients showed that Clozapine is more effective in producing a shift towards improvement at the end of 6 weeks. Major side effects reported in Clozapine confirmed sedation and hypersalivation as consistent problems and presence of rigidity and tremor (extra-pyramidal) being at variance with other studies.

Genetic Etiology of Spelling Deficits in the Colorado and London Twin Studies of Reading Disability

The basic multiple regression model for the analysis of selected twin data (DeFries and Fulker 1985, 1988) was fitted to spelling data from 100 pairs of MZ twins and 71 pairs of same-sex DZ twins tested in the Colorado Reading Project (DeFries, Olson, Pennington and Smith 1991), and to data from 12 pairs of MZ twins and 15 pairs of same-sex DZ twins tested in the London twin study of reading disability (Stevenson, Graham, Fredman and McLoughlin 1984, 1987). Estimates of hg2 obtained from analyses of these data suggest that about 60% of the deficit of probands is due to heritable influences in both samples. When a regression model was fitted separately to data from males and females in the combined Colorado and London samples, resulting estimates of hg2 were 0.66±0.18 and 0.56±0.19, respectively, a nonsignificant difference. Collaborative analyses of data from additional twin studies of reading disability would facilitate more rigorous tests of hypotheses of differential genetic etiology as a function of group membership.

Temperament and Psychiatric Disorder: The Genetic Contribution to Behaviour in Childhood

The studies stemming from the New York longitudinal study of temperament in childhood are summarised and conceptual difficulties and problems arising from them are described. An alternative model of temperament provided by Buss and Plomin is also considered. Finally, a new typology of temperament is proposed. It is based on the suggestion that ordinary, non-pathological behaviours, in extreme form, can be viewed as manifestations of emotional disorder, hyperactivity and antisocial disorder. Empirical evidence derived both from twin studies and from epidemiological investigations is put forward to support this view.

The evaluation of home based speech therapy for language delayed pre-school children in an inner city area.

This study reports a controlled trial of home based speech therapy for children with delayed language development living in an inner city area. Details of the six month therapy are given. Good parental cooperation was achieved. Both the experimental and control groups made significant gains over the six month period and in only one measure had the experimental group done better than the control group. The factors are discussed that would mitigate against these children attending clinics regularly. The study emphasizes the difficulties inherent in assessing therapy and stresses the need for adequate controls in carrying out such work.

Multivariate Statistics. IV. Statistical Issues in Identifying Vulnerability and Protective Factors Log-Linear Analysis

This is the last of four papers considering the application of multivariate statistics in psychiatric research. The relevance of log-linear analysis with multiway contingency table data is described. The problems of identifying vulnerability factors in life-event research are discussed. The conclusion is reached that non-hierarchical models need to be tested to provide a sensible operational definition of vulnerability with such data. An illustration of a non-hierarchical log-linear analysis is provided.