Schizophrenia and mental handicap: an historical review, with implications for further research

Lifetime prevalence of schizophrenia among individuals prenatally exposed to atomic bomb radiation in Nagasaki City

OBJECTIVE

The aim of this study was to examine the relationship between prenatal exposure to atomic bomb (A-bomb) radiation and the development of schizophrenia in adulthood.

METHOD

We investigated the lifetime prevalence of schizophrenia among people prenatally exposed to the 1945 Nagasaki A-bomb, using the schizophrenia register and the A-bomb survivors' database.

RESULTS

Among 1867 prenatally exposed individuals, 18 subjects (0.96%) had developed schizophrenia later in life. The prevalence was significantly higher in people exposed in the second trimester of pregnancy than in those exposed in the third trimester. The closer they had been to the hypocentre, the higher was the prevalence, but no statistically significant linear relationship was seen.

CONCLUSION

This investigation could not clarify the nature of exposure to A-bomb radiation as a risk factor for schizophrenia in the prenatal period.

22q11 deletion syndrome: a genetic subtype of schizophrenia

Schizophrenia is likely to be caused by several susceptibility genes and may have environmental factors that interact with susceptibility genes and/or nongenetic causes. Recent evidence supports the likelihood that 22q11 Deletion Syndrome (22qDS) represents an identifiable genetic subtype of schizophrenia. 22qDS is an under-recognized genetic syndrome associated with microdeletions on chromosome 22 and a variable expression that often includes mild congenital dysmorphic features, hypernasal speech, and learning difficulties. Initial evidence indicates that a minority of patients with schizophrenia (approximately 2%) may have 22qDS and that prevalence may be somewhat higher in subpopulations with developmental delay. This paper proposes clinical criteria (including facial features, learning disabilities, hypernasal speech, congenital heart defects and other congenital anomalies) to aid in identifying patients with schizophrenia who may have this subtype and outlines features that may increase the index of suspicion for this syndrome. Although no specific causal gene or genes have yet been identified in the deletion region, 22qDS may represent a more homogeneous subtype of schizophrenia. This subtype may serve as a model for neurodevelopmental origins of schizophrenia that could aid in delineating etiologic and pathogenetic mechanisms.

Volumetric magnetic resonance imaging study of the brain in subjects with sex chromosome aneuploidies

OBJECTIVES

Cognitive impairment has been reported in people with sex chromosome aneuploides (SCAs) and it has been proposed that the presence of an extra sex chromosome may have an adverse effect on neurodevelopment. This study examines the hypothesis with structural MRI of the brain.

METHODS

Thirty two subjects with SCA (XXX (n=12), XYY (n=10), and XXY (n=10)) from a birth cohort study were matched groupwise for age, parental social class, and height with normal controls (13 female, 26 male). Brain MRI, measurements of IQ, and a structured psychiatric interview were performed.

RESULTS

The XXX females and XXY males had significantly smaller whole brain volumes than controls of the same phenotypic sex (p=0.003 and p</=0.05 respectively). The XXY group also had bilaterally enlarged lateral ventricles (p</=0.05). No significant differences were found between the XYY group and controls. IQ scores in all SCA groups were lower than in the control groups.

CONCLUSIONS

The main result of reduced brain volumes in XXX and XXY subjects, but not in XYY subjects, indicates that the presence of a supernumerary X chromosome has a demonstrable effect on brain development.

'Pfropfschizophrenie' revisited. Schizophrenia in people with mild learning disability

BACKGROUND

It is reported that people with mild learning disability have a higher point prevalence of schizophrenia than the normal population, the reasons for which are unclear.

METHOD

Thirty-nine subjects with mild learning disability and schizophrenia, 34 control subjects with schizophrenia and 28 control subjects with mild learning disability were seen. Interviews with relatives and carers were also conducted. Assessments were made of clinical variables, psychopathology, neurological 'soft' signs, IQ, memory and family history. Blood was taken for karyotypic analysis from comorbid subjects.

RESULTS

The comorbid group had more negative symptoms, episodic memory deficits, soft neurological signs, epilepsy and receive more community supports than control subjects with schizophrenia. Comorbid subjects had a tendency to belong to multiply affected families and show high rates of chromosomal variants on routine karyotypic testing.

CONCLUSIONS

Future work on the generality of schizophrenia should include people with premorbid learning disability, as a discrete subtype from whom valuable genetic aetiological clues may be obtained.

Schizophrenia in people with intellectual disability: the role of pregnancy and birth complications

The literature suggests that mental illness is more common in people with intellectual disability than in the general population. Having reviewed the literature, Turner (1989) [Psychological Medicine 19, 301-14] suggested that about 3% of people with intellectual disability also have schizophrenia. As pregnancy and birth complications (PBCs) occur more commonly in people with intellectual disability than in the general population and are also implicated in the aetiology of schizophrenia, it is possible that these conditions share a common aetiology. This study reports on the occurrence of PBCs in those people with intellectual disability who develop schizophrenia. Fifty people with intellectual disability and schizophrenia were matched for age, sex, degree of intellectual disability and presence of epilepsy with a control group who did not suffer from schizophrenia or a schizophreniform psychosis. The obstetric history was obtained and events rated on a scale specifically designed for this study. This PBCs scale consists of six sub-scales covering areas of general maternal health, pregnancy, delivery, medication in labour, total medication score and neonatal score, as well as an overall total score. The study found that people with intellectual disability who develop schizophrenia have significantly higher rates of PBCs than controls. All of the sub-scales on the PBCs scale were significantly higher in people with schizophrenia, with the exception of the medication scales. Only five out of the 50 people with schizophrenia had not had a major obstetric complication, compared to 13 subjects from the control group. A number of abnormalities were specifically higher in people who later developed schizophrenia. These included: abnormally long or short labour; maternal episiotomy; maternal preeclamptic toxaemia; induction of labour; dysmaturity; maternal smoking in pregnancy; and a delay in neonatal crying. The results suggest that PBCs are important in the aetiology of schizophrenia in people with intellectual disability.

Prenatal exposure to influenza epidemics and risk of mental retardation

This study was undertaken to determine whether prenatal exposure to influenza epidemics increases the risk of mental handicap. The monthly birth frequencies of 827 first-admission individuals (mean age at admission 13 years) with a primary diagnosis of non-specific mental retardation, discharged from psychiatric hospitals in England and Wales, were examined in relation to the monthly death rates from influenza over the period 1953-1980. The relative risk of developing mental handicap when exposed to influenza epidemics during mid-gestation was assessed by a generalized linear model. Increased death rates from influenza, a measure of prevalence of the infection, were significantly associated with an increase in births of mentally handicapped individuals 6 months later. For every 1000 female deaths from influenza there was a 17% increase in births of mentally handicapped individuals 6 months later. Maternal exposure to influenza at approximately the third to fourth month of gestation may be risk factor for developing mental handicap.

Psychiatry and learning disability

My involvement with the psychiatry of learning disability began in 1968 when Professor Batchelor, then Professor of Psychiatry at the University of Dundee, suggested that mental illness in people with learning disability was a clinically interesting and under-researched topic which merited further investigation. At that time, mental illness was not usually considered even a part of the medical specialty of learning disability – or at least, not in Scotland. People in mental handicap hospitals who developed signs of mental illness were normally passed on to colleagues in general psychiatry who were considered to have the investigative and treatment expertise. If admission to in-patient care was considered necessary, it was usually to the local general psychiatry service.

Mental illness-mental retardation in the United States: policy and treatment challenges

The purpose of this paper is to present an overview of current trends in the field of dual diagnosis in the United States. Policy, programme, diagnostic and treatment issues are reviewed. The paper will examine the effects of the social policy of deinstitutionalization on people who have a dual diagnosis and will offer policy ideas for ameliorating some of the significant obstacles facing this population. Exemplary programme models are briefly discussed to illustrate the development of effective services. The challenges of assessing psychopathology in people with mental retardation are addressed. Several therapy and treatment modalities that have proven to be effective with people who have a dual diagnosis are also discussed. Lastly, this paper mentions a new community ideology driven by the values of consumers choice and satisfaction.

Chromosomal aberrations and schizophrenia. Autosomes

Chromosomal aberrations associated with schizophrenic disorders may suggest regions in which to focus a search for genes predisposing to schizophrenia by a linkage strategy. As for other genetic illnesses, chromosomal abnormalities may also provide useful tools for subsequent physical mapping, fine localisation, and isolation of important susceptibility genes. Identification of several chromosomal aberrations may be especially important, given the unknown pathophysiology, the paucity of known brain genes, and the probable genetic heterogeneity of schizophrenia and manic-depression. However, because psychiatric disorders are common and inherited in a complex manner, researchers must use caution when drawing inferences about associations with chromosomal aberrations. Reported abnormalities involving autosomes (chromosomes 1-22) associated with psychotic disorders are reviewed. Their relevance to linkage studies localising genes for schizophrenia was estimated by standardised criteria for specificity, diagnosis, family history, and overall weight of evidence. Four 'possibly relevant' chromosomal regions were identified: 5q, 11q, 18q, and 19p. This paper outlines strategies for future studies to detect new chromosomal aberrations associated with major psychotic disorders that may be relevant to isolating the genes for schizophrenia.

Current developments in the understanding of mental retardation. Part II: Psychopathology

During recent years there has been greater recognition of the impressive degree of psychiatric disturbance that affects those with mental retardation. An increasing number of systematic studies are focusing on the prevalence, risk factors, and clinical characteristics of psychiatric disturbance within this population. In addition, traditional neuropsychiatric assessment and treatment approaches are being evaluated, and new approaches are being developed. Such efforts will undoubtedly improve the ability to effectively diagnose and treat mentally retarded individuals suffering from psychiatric disorders. This paper is the second of two reviews that explore several recent developments in biological, phenomenological, and psychopathological aspects of mental retardation.

Psychometric assessment of psychiatric disorders in people with learning difficulties (mental handicap): a review of measures

Instruments designed to assess psychiatric disorders in people with learning difficulties (mental handicap) were critically reviewed from a psychometric perspective. Major trends were found in the assessment of psychopathology related to DSM-III and depressive disorders although research in other areas was patchy. Although some psychometrically sophisticated measures were identified the area was characterized by an absence of important psychometric data for many measures. Future research should attend to developing assessments of schizophrenia, psycho-sexual disorders, adjustment disorders and the validation of screening procedures and instrument formats. Future studies should include more people with severe and profound learning difficulties.

Assessing schizophrenia in adults with mental retardation. A comparative study

Twenty-five patients with mild mental retardation were compared with 26 schizophrenic patients of normal intelligence. The patients with retardation had suffered an earlier onset and were less likely to have been married or employed. However, the clinical phenomena exhibited by the two groups, as elicited by a SADS-L interview, were very similar. Thus, standardised interviews and criteria for schizophrenia can be readily applied to those with an IQ between 50 and 70.

Cognitive functioning and symptomatology in chronic schizophrenia

Chronic schizophrenic patients in a long stay hospital were found to have low levels of intelligence (mean IQ of 80), which was attributed to the effects of substantial intellectual deterioration on below average pre-morbid levels of functioning. Patients with the lowest IQ scores had the least severe positive symptoms but symptomatology was not related to age or extent of intellectual decline. Speed of functioning was relatively more impaired than level of intellectual functioning, with cognitive speed being more affected than motor speed. The severity of negative but not positive symptoms was significantly related to the severity of bradyphrenia (cognitive slowing), a result which would be consistent with the notion of a subcortical pathology in patients with Type II schizophrenia.