Genetics advances and learning disability

Clinical psychologists' attitudes towards the biology and 'new genetics' of intellectual and developmental disabilities: a pilot study using Q-methodology

BACKGROUND

The current study investigated how ideas and models from the 'New Genetics' and associated fields of developmental neuroscience and behavioural phenotypes are perceived by clinical psychologists working with people with intellectual and developmental disabilities (IDD). As well as examining the take-up and influence of such ideas, it also examines barriers, both personal and institutional, to the widespread adoption of such concepts and research findings in services for people with IDD.

METHODS

A Q-methodology study was undertaken with 31 qualified and 16 trainee clinical psychologists in the North West of England using a specifically developed 81-item Q set.

RESULTS

Three factors were identified and labelled Integration of social and medical models, Social model of disability is more helpful and Genetic advances in conflict with recognising the value of people with IDD.

CONCLUSION

There was a lack of consensus in clinical psychologists working with people with IDD, with amount and type of professional experience affecting the factor loadings, which may need to be considered in developing clinical applications of genetic IDD research.

A case of ADHD and a major Y chromosome abnormality

BACKGROUND

ADHD is a common, heritable disorder of childhood. Sex chromosome abnormalities are relatively rare conditions that are sometimes associated with behavioral disorders.

METHOD

The authors present a male child with ADHD and a major de-novo Y chromosome abnormality consisting of deletion of the long arm and duplication of the short arm. It is possible that the Y chromosomal abnormality is causing the ADHD syndrome in this boy.

CONCLUSION

Considering this case and considering that (a) ADHD is more common in boys than in girls, (b) the transmission of some genes associated with ADHD may occur preferentially from fathers rather than from mothers, and (c) ADHD is more common in children with XYY syndrome and Turner's syndrome than in other children, the authors propose that the sex chromosomes may contain risk genes for ADHD.

Elevated rates of schizophrenia in a familial sample with mental illness and intellectual disability

BACKGROUND

It is unknown whether intellectual disability (ID) is more familially related to psychotic mood disorders or schizophrenia. L. S. Penrose's large sample of families with two or more members admitted to psychiatric hospitals provided a unique opportunity to investigate the familial relationship between mild ID, schizophrenia and psychotic affective disorders.

METHOD

There were 183 affected relative pairs comprising probands with mild ID (95 male, 88 female) and their first or second degree relatives with schizophrenia or psychotic affective disorder.

RESULTS

There were nearly twice as many relatives with a diagnosis of schizophrenia (n = 121) as relatives with affective disorders (n = 62) among the intellectually impaired probands. This excess of schizophrenia was statistically significant, even after accounting for the increased risk of hospitalization for schizophrenia (P = 0.005), and was fairly constant across the different relative types. First-degree relatives with either mental illness were more likely to be parents (n = 77) than siblings (n = 51) or children (n = 3), but there was no excess of mother-son pairs.

CONCLUSIONS

These results suggest a stronger familial relationship of ID with schizophrenia than psychotic affective disorder, and lend some support to the neurodevelopmental hypothesis of schizophrenia.

Patterns of dysmorphic features in schizophrenia

Congenital dysmorphic features are prevalent in schizophrenia and may reflect underlying neurodevelopmental abnormalities. A cluster analysis approach delineating patterns of dysmorphic features has been used in genetics to classify individuals into more etiologically homogeneous subgroups. In the present study, this approach was applied to schizophrenia, using a sample with a suspected genetic syndrome as a testable model. Subjects (n = 159) with schizophrenia or schizoaffective disorder were ascertained from chronic patient populations (random, n = 123) or referred with possible 22q11 deletion syndrome (referred, n = 36). All subjects were evaluated for presence or absence of 70 reliably assessed dysmorphic features, which were used in a three-step cluster analysis. The analysis produced four major clusters with different patterns of dysmorphic features. Significant between-cluster differences were found for rates of 37 dysmorphic features (P < 0.05), median number of dysmorphic features (P = 0.0001), and validating features not used in the cluster analysis: mild mental retardation (P = 0.001) and congenital heart defects (P = 0.002). Two clusters (1 and 4) appeared to represent more developmental subgroups of schizophrenia with elevated rates of dysmorphic features and validating features. Cluster 1 (n = 27) comprised mostly referred subjects. Cluster 4 (n = 18) had a different pattern of dysmorphic features; one subject had a mosaic Turner syndrome variant. Two other clusters had lower rates and patterns of features consistent with those found in previous studies of schizophrenia. Delineating patterns of dysmorphic features may help identify subgroups that could represent neurodevelopmental forms of schizophrenia with more homogeneous origins.