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There is increasing evidence for shared genetic susceptibility between schizophrenia and bipolar disorder. Although genetic variants only convey subtle increases in risk individually, their combination into a polygenic risk score constitutes a strong disease predictor.
To investigate whether schizophrenia and bipolar disorder polygenic risk scores can distinguish people with broadly defined psychosis and their unaffected relatives from controls.
Using the latest Psychiatric Genomics Consortium data, we calculated schizophrenia and bipolar disorder polygenic risk scores for 1168 people with psychosis, 552 unaffected relatives and 1472 controls.
Patients with broadly defined psychosis had dramatic increases in schizophrenia and bipolar polygenic risk scores, as did their relatives, albeit to a lesser degree. However, the accuracy of predictive models was modest.
Although polygenic risk scores are not ready for clinical use, it is hoped that as they are refined they could help towards risk reduction advice and early interventions for psychosis.
Declaration of interest
R.M.M. has received honoraria for lectures from Janssen, Lundbeck, Lilly, Otsuka and Sunovian.
Numerous studies have reported neuropsychological impairment in schizophrenia and increasing evidence suggests that individuals with schizophrenia or schizophrenia spectrum disorders and their unaffected first-degree family members exhibit similar deficits in some neuropsychological domains. Substantial modifications to the Wechsler Memory Scale (WMS) have resulted in more sensitive and reliable indicators of various aspects of memory functioning in the WMS-III, which enables generation of auditory, visual and working memory indices.
The aim of the present study was to examine the memory profile of individuals with schizophrenia or schizophrenia spectrum disorder (n = 19), their unaffected first-degree family members (n = 11), and healthy controls (n = 9).
The study involved neuropsychological testing, including the immediate and working memory subtests of the WMS-III, utilizing both auditory and visual domains. Symptom assessment was performed using the Schedules for Clinical Assessment in Neuropsychiatry (SCAN), version 2.0. Two multivariate analyses of covariance (mancova) were conducted: (i) comparing patients, relatives and controls; and (ii) comparing relatives and controls only.
The first analysis indicated that the patient group obtained significantly lower index scores than both relatives and controls on all three indices. The second analysis indicated that the performance of relatives was significantly lower than controls on the working memory index, although there were no significant differences on the auditory and visual immediate index scores.
The differential impairment in working memory performance in clinically asymptomatic family members suggests that the WMS-III working memory index score may be a potential phenotypic marker of schizophrenia.
Recent evidence points to partially shared genetics of neuropsychiatric disorders.
We examined risk of intellectual disability and other neuropsychiatric outcomes in 3174 children of mothers with schizophrenia, bipolar disorder or unipolar major depression compared with 3129 children of unaffected mothers.
We used record linkage across Western Australian population-based registers. The contribution of obstetric factors to risk of intellectual disability was assessed.
Children were at significantly increased risk of intellectual disability with odds ratios (ORs) of 3.2 (95% CI 1.8–5.7), 3.1 (95% CI 1.9–4.9) and 2.9 (95% CI 1.8–4.7) in the maternal schizophrenia, bipolar disorder and unipolar depression groups respectively. Multivariate analysis suggests familial and obstetric factors may contribute independently to the risk. Although summated labour/delivery complications (OR = 1.4, 95% CI 1.0–2.0) just failed to reach significance, neonatal encephalopathy (OR = 7.7, 95% CI 3.0–20.2) and fetal distress (OR = 1.8, 95% CI 1.1–2.7) were independent significant predictors. Rates of rare syndromes in children of mothers with mental disorder were well above population rates. Risk of pervasive developmental disorders, including autism, was significantly elevated for children of mothers with bipolar disorder. Risk of epilepsy was doubled for children of mothers with unipolar depression.
Our findings provide epidemiological support for clustering of neuropsychiatric disorders. Further larger epidemiological studies are warranted.
A population-based record linkage case cohort of 239,995 births, to 119,214 women, born in Western Australia from 1980 to 2001 inclusive, was used to measure the recording of selected indicators of maternal health (current and prior) during pregnancy. We compared records of women with singleton pregnancies with that in twin pregnancies Mothers of first- and second-born singletons (n = 117,647) were compared with women with a first-born singleton followed by twins (n = 1,567). Binary indicators were used to calculate population prevalence of medical conditions, pregnancy complications and birth outcomes. Infant outcomes included stillbirth, low birthweight, preterm birth and birth defects. Women with twins were significantly older and taller, with similar rates of medical conditions and pregnancy complications during first singleton pregnancies compared with women with two consecutive singletons. However, during their second pregnancy, women with twins had significantly higher rates of essential hypertension, pre-eclampsia, threatened abortion, premature rupture of the membranes and ante partum hemorrhage with abruption than women with singletons. For both groups, maternal conditions in the first pregnancy were underreported in the second pregnancy, including diabetes, epilepsy, asthma, chronic renal dysfunction and essential hypertension. At the second birth, twins were 3 times more likely to be stillborn, 17 times more likely to be low birthweight and 4 times more likely to be delivered preterm compared with singletons. This research demonstrates the importance for epidemiologists and others, of having access to a complete maternal medical history for analyses of risks associated with maternal, infant and childhood morbidity.
Aims – The Diagnostic Interview for Psychoses (DIP) is a comprehensive interview schedule for psychotic disorders, linked to the OPCRIT diagnostic algorithm, bridging the gap between fully structured, lay-administered schedules and semistructured, psychiatrist-administered interviews. Here we describe the validity, reliability and applications of the Italian version of the DIP. Methods – The interview was translated into Italian and its content validity tested by back translation. Sixty patients, drawn from among those who contacted the South-Verona Community Mental Health Service, were included in the study. Each patient was first assessed independently by two raters, one of whom conducted the interview, while the other assumed the role of observer. Subsequently (median: 89 days), 44 of these patients were re-interviewed by a third rater, who made an independent assessment. Diagnostic validity was assessed in 18 cases, interviewed with the DIP and using the SCAN as ‘gold standard. Results – The mean duration of the interview was 37 minutes for the inter-rater interviews and 39 minutes for the retest interviews. Good to excellent inter-rater reliability was demonstrated for both ICD-10 and DSM-IV diagnoses, while in the test-retest reliability pairwise agreement was high for half of the items. Diagnostic validity was good, with twelve out of the 18 DIP-OPCRIT diagnoses (67%) matching the SCAN diagnosis. Conclusions – Overall, the results support the reliability and validity of the Italian translation of the DIP. The Italian version will be useful both in routine practice to establish standard reference diagnoses of psychosis and in the research field, where it can be used by academic researchers in clinical trials and epidemiological studies.
In recent years, there has been a marked increase in the use of psychiatric case registers for research purposes. Registers are a valuable data asset but there are no standard guidelines for evaluating their use in research. It is becoming increasingly important for researchers who use register data, and journal editors who publish their work, to set benchmarks to assess the quality of a register and its research application. Several criteria that could form the basis of such an evaluative framework are discussed. The discussion is illustrated using a Western Australian e-cohort of half a million children for whom we have assembled comprehensive data cross-linked across a number of administrative registers.
In the revision process leading up to DSM–V and ICD–11, it is important to highlight both similarities and differences between the two classifications. Where irreconcilable conceptual differences are involved, these should be stated in a manner inviting future research to elucidate the advantages and disadvantages of alternative concepts or definitions. Eventually, both DSM–V and ICD–11 will need to be assessed against a set of benchmarks of validity and utility.
The epidemiology of intellectual disability co-occurring with schizophrenia and other psychiatric illness is poorly understood. The separation of mental health from intellectual disability services has led to a serious underestimation of the prevalence of dual diagnosis, with clinicians ill-equipped to treat affected individuals.
To estimate the prevalence of dual diagnosis and describe its clinical profile.
The Western Australian population-based psychiatric and intellectual disability registers were cross-linked (total n=245 749).
Overall, 31.7% of people with an intellectual disability had a psychiatric disorder; 1.8% of people with a psychiatric illness had an intellectual disability. Schizophrenia, but not bipolar disorder and unipolar depression, was greatly overrepresented among individuals with a dual diagnosis: depending on birth cohort, 3.7–5.2% of those with intellectual disability had co-occurring schizophrenia. Pervasive developmental disorder was identified through the Intellectual Disability Register and is therefore limited to individuals with intellectual impairment. None the less, pervasive developmental disorder was more common among people with a dual diagnosis than among individuals with intellectual disability alone. Down syndrome was much less prevalent among individuals with a dual diagnosis despite being the most predominant cause of intellectual disability. Individuals with a dual diagnosis had higher mortality rates and were more disabled than those with psychiatric illness alone.
The facility to combine records across administrative jurisdictions has enhanced our understanding of the epidemiology of dual diagnosis, its clinical manifestations and aetiological implications. In particular, our results are suggestive of a common pathogenesis in intellectual disability co-occurring with schizophrenia.
Two international classifications currently dominate research and clinical practise; the International Classification of Diseases (ICD)-10 and the Diagnostic and Statistical Manual of Mental Disorders (DSM)-IV. Both classifications provide detailed descriptions of all the main psychiatric syndromes, personality disorders and other disorders of behaviour or function. The first comprehensive nosology covering an entire range of diseases and including a classification of mental illness was produced by the newly formed World Health Organisation (WHO) in 1948. The WHO has the responsibility to produce regular revisions of the ICD for international use. Disorders in ICD-10 are arranged in groups according to major common themes or descriptive likenesses. DSM-IV has more categories than ICD-10, which may reflect the requirements of the health care system in the United States. The International Personality Disorder Examination (IPDE) assesses the phenomena and life experiences that are relevant to the diagnoses of personality disorders in DSM-IV and ICD-10.
Schizophrenia has a special place in the field of psychiatry in general and cultural psychiatry in particular. This was the first psychiatric condition which was studied across cultures under the aegis of the World Health Organisation (WHO). The two studies – the International Pilot Study of Schizophrenia and Determinants of Outcome of Severe Mental Disorders – set the benchmark for comparing illnesses across cultures. While welcomed by the epidemiologists that similar epidemiological methods can be employed across cultures, the critique by anthropologists and social scientists claimed that these studies looked at commonalities and ignored the differences. There is also some evidence that the outcome of schizophrenia appears to be better in low-income countries, although these findings have been challenged.
Jablensky, as one of the original scientists involved in the WHO studies, provides an overview of schizophrenia research across cultures. He gives a brief introduction to the epidemiology but focuses on phenotypic comparability of schizophrenia across populations. This is an important point if one is to deal with the question of misdiagnosis, which is sometimes seen as conflating the rates of schizophrenia. He emphasises that schizophrenic disorders in non-Western populations can be reliably distinguished from the acute transient psychoses and other disorders such as affective disorders, although he acknowledges that there may be some symptomatic overlap between affective disorders and schizophrenia. Jablensky cautions that a good deal of the variation may be attributed to methodological difficulties, including study design, sample size, diagnostic patterns and methods of data analysis. The real variation noted in these rates is possibly related to the multifactorial nature of the illness.