Over the past two decades, mental retardation research converges on three general themes: co-occurring mental retardation and psychopathology; families of offspring with mental retardation; and the developmental approach regarding behavioral sequences and profiles. Intertwined with each theme is a mounting body of research on genetic mental retardation syndromes. We first review recent progress in each of the three domains—psychopathology, families, and development—based on studies of groups with heterogenous or nonspecific mental retardation. We then show how new findings from specific genetic syndromes take this knowledge even further, as well as aid in the search for genetic, physiological, and environmental mechanisms associated with certain behaviors. We end the review by briefly summarizing our reasons for promoting an etiological approach to future mental retardation research, as well as by discussing methodological and other challenges.

This paper describes an intervention with a man who has Prader-Willi Syndrome (PWS) and mild learning disabilities in a residential setting. PWS is a chromosomal disorder that is characterized by a wide range of behavioural characteristics including overeating and challenging behaviour. The intervention was based on a range of principles derived from a motivational interviewing approach, which were embedded in a broader behavioural framework that was designed to assist in weight reduction and reduce challenging behaviour. Records of weight and challenging behaviour kept over time suggest that the approach had relatively little impact on overall weight. However, levels of challenging behaviour were reduced quickly and have been maintained at a stable and lower level. Weight has also been maintained at a reasonably constant level without confrontation with staff or excessive restrictions on the individual concerned. Relationships between the individual and staff in the home also improved over the course of the intervention.

Recent advances are reviewed in understanding the heightened prevalence of psychopathology and maladaptive behavior among children with intellectual disability. Researchers have traditionally emphasized measurement and prevalence issues, using either psychiatric assessments or rating scales to identify the prevalence of various problems in children with intellectual disability. Yet the time is ripe to shift directions, and identify more precisely why children are at increased risk for psychopathology to begin with. Although several “bio- psycho-social” hypotheses are reviewed, a particularly promising line of work links psychopathology to genetic intellectual disability syndromes. Psychiatric vulnerabilities in several syndromes are reviewed, as are the advantages of phenotypic work for understanding psychopathology among children with intellectual disability more generally.

The personality profiles for youths with Prader-Willi, fragile-X, or Williams syndrome were compared to three matched groups attending regular schools. Using the California Child Q-Set (CCQ), both of the parents of the 39 children with Prader-Willi syndrome, 32 boys with fragile-X syndrome, 28 children with Williams syndrome, and children in the comparison groups provided independent personality descriptions in terms of the Big Five personality factors of Extraversion, Agreeableness, Conscientiousness, Emotional Stability, and Openness, along with Motor Activity and Irritability. Specific personality phenotypes for each of the three syndrome groups were found to be differentially related to parental behaviours (i.e. control and anger) and family contexts (i.e. experienced family stress, marital conflict, and parental consistency).

Prader-Willi syndrome is a genetic illness associated with a defect on chromosome 15. It presents with hypotonicity in infancy followed by voracious appetite and gross obesity from early childhood and with a range of other clinical and behavioural sequelae. This case report is of an adolescent boy who was admitted to a psychiatric unit for an intensive behavioural programme to control his weight gain and deal with associated behavioural problems, and demonstrates that an inpatient programme can lead to sustainable improvements in weight control and other indicators of well-being in PWS patients.

We report on a Prader-Willi syndrome (PWS) patient carrier of a balanced 15q15q translocation and affected by a prolactin-secreting pituitary adenoma. Evidence provided by molecular studies indicates that the structural rearrangement is an isochromosome of maternal origin. According to the identification of isodisomy as the basis of the association of rare disorders and the recent report on chromosome 15 monosomy and nullisomy in pituitary adenoma, we suggest that in our case PWS and pituitary adenoma might be related.

A group of 30 patients clinically described as having the Prader-Willi Syndrome (PWS) were studied using microsatellites from 15q11-13 and methylation analysis with probe PW71B (D15S63). The patients were categorized according to clinical symptoms. 80% of all patients were informative using molecular and cytogenetic methods. Among 8 patients with an atypical PWS phenotype, 2 showed uniparental disomy, and 2 had a mosaic deletion for 15q. The last 4 atypical and 2 typical patients had neither molecular defects confirmed by microsatellite analysis nor a parent-of-origin-specific methylation pattern for PWS. Our results confirm that methylation pattern analysis provides an additional and alternative microsatellite analysis to diagnose PWS.

A 21 year-old woman with Prader-Willi syndrome (PWS) and a delusional disorder (paranoid psychosis) is described. Other reports of psychoses associated with PWS are reviewed. Reasons for the co-existence of the two disorders are considered, with discussion of the possible role of auditory information processing deficits in the genesis of psychotic symptoms. Such symptoms must be differentiated from maladaptive behaviours not arising from psychosis, the latter being relatively common in PWS. Treatment with a small dose of flupenthixol greatly reduced the impact of the patient's psychotic symptoms, with a corresponding improvement in her quality of life.