Fine-mapping genomic loci refines bipolar disorder risk genes

Bipolar disorder (BD) is a heritable mental illness with complex etiology. While the largest published genome-wide association study identified 64 BD risk loci, the causal SNPs and genes within these loci remain unknown. We applied a suite of statistical and functional fine-mapping methods to these loci, and prioritized 22 likely causal SNPs for BD. We mapped these SNPs to genes, and investigated their likely functional consequences by integrating variant annotations, brain cell-type epigenomic annotations, brain quantitative trait loci, and results from rare variant exome sequencing in BD. Convergent lines of evidence supported the roles of SCN2A, TRANK1, DCLK3, INSYN2B, SYNE1, THSD7A, CACNA1B, TUBBP5, PLCB3, PRDX5, KCNK4, AP001453.3, TRPT1, FKBP2, DNAJC4, RASGRP1, FURIN, FES, YWHAE, DPH1, GSDMB, MED24, THRA, EEF1A2, and KCNQ2 in BD. These represent promising candidates for functional experiments to understand biological mechanisms and therapeutic potential. Additionally, we demonstrated that fine-mapping effect sizes can improve performance and transferability of BD polygenic risk scores across ancestrally diverse populations, and present a high-throughput fine-mapping pipeline (https://github.com/mkoromina/SAFFARI).

Mapping genomic loci implicates genes and synaptic biology in schizophrenia

Schizophrenia has a heritability of 60-80%1, much of which is attributable to common risk alleles. Here, in a two-stage genome-wide association study of up to 76,755 individuals with schizophrenia and 243,649 control individuals, we report common variant associations at 287 distinct genomic loci. Associations were concentrated in genes that are expressed in excitatory and inhibitory neurons of the central nervous system, but not in other tissues or cell types. Using fine-mapping and functional genomic data, we identify 120 genes (106 protein-coding) that are likely to underpin associations at some of these loci, including 16 genes with credible causal non-synonymous or untranslated region variation. We also implicate fundamental processes related to neuronal function, including synaptic organization, differentiation and transmission. Fine-mapped candidates were enriched for genes associated with rare disruptive coding variants in people with schizophrenia, including the glutamate receptor subunit GRIN2A and transcription factor SP4, and were also enriched for genes implicated by such variants in neurodevelopmental disorders. We identify biological processes relevant to schizophrenia pathophysiology; show convergence of common and rare variant associations in schizophrenia and neurodevelopmental disorders; and provide a resource of prioritized genes and variants to advance mechanistic studies.

Genome-wide association study of more than 40,000 bipolar disorder cases provides new insights into the underlying biology

Bipolar disorder is a heritable mental illness with complex etiology. We performed a genome-wide association study of 41,917 bipolar disorder cases and 371,549 controls of European ancestry, which identified 64 associated genomic loci. Bipolar disorder risk alleles were enriched in genes in synaptic signaling pathways and brain-expressed genes, particularly those with high specificity of expression in neurons of the prefrontal cortex and hippocampus. Significant signal enrichment was found in genes encoding targets of antipsychotics, calcium channel blockers, antiepileptics and anesthetics. Integrating expression quantitative trait locus data implicated 15 genes robustly linked to bipolar disorder via gene expression, encoding druggable targets such as HTR6, MCHR1, DCLK3 and FURIN. Analyses of bipolar disorder subtypes indicated high but imperfect genetic correlation between bipolar disorder type I and II and identified additional associated loci. Together, these results advance our understanding of the biological etiology of bipolar disorder, identify novel therapeutic leads and prioritize genes for functional follow-up studies.

Estimation of Genetic Correlation via Linkage Disequilibrium Score Regression and Genomic Restricted Maximum Likelihood

Genetic correlation is a key population parameter that describes the shared genetic architecture of complex traits and diseases. It can be estimated by current state-of-art methods, i.e., linkage disequilibrium score regression (LDSC) and genomic restricted maximum likelihood (GREML). The massively reduced computing burden of LDSC compared to GREML makes it an attractive tool, although the accuracy (i.e., magnitude of standard errors) of LDSC estimates has not been thoroughly studied. In simulation, we show that the accuracy of GREML is generally higher than that of LDSC. When there is genetic heterogeneity between the actual sample and reference data from which LD scores are estimated, the accuracy of LDSC decreases further. In real data analyses estimating the genetic correlation between schizophrenia (SCZ) and body mass index, we show that GREML estimates based on ∼150,000 individuals give a higher accuracy than LDSC estimates based on ∼400,000 individuals (from combined meta-data). A GREML genomic partitioning analysis reveals that the genetic correlation between SCZ and height is significantly negative for regulatory regions, which whole genome or LDSC approach has less power to detect. We conclude that LDSC estimates should be carefully interpreted as there can be uncertainty about homogeneity among combined meta-datasets. We suggest that any interesting findings from massive LDSC analysis for a large number of complex traits should be followed up, where possible, with more detailed analyses with GREML methods, even if sample sizes are lesser.

Intellectual disability and other neuropsychiatric outcomes in high-risk children of mothers with schizophrenia, bipolar disorder and unipolar major depression

BACKGROUND

Recent evidence points to partially shared genetics of neuropsychiatric disorders.

AIMS

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.

METHOD

We used record linkage across Western Australian population-based registers. The contribution of obstetric factors to risk of intellectual disability was assessed.

RESULTS

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.

CONCLUSIONS

Our findings provide epidemiological support for clustering of neuropsychiatric disorders. Further larger epidemiological studies are warranted.

From inventory to benchmark: quality of psychiatric case registers in research

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.

Do women express and experience psychosis differently from men? Epidemiological evidence from the Australian National Study of Low Prevalence (Psychotic) Disorders

OBJECTIVE

To examine how women differ from men in their expression and experience of psychosis.

METHOD

Using an epidemiological sampling frame, 1090 cases of psychosis (schizophrenia, schizoaffective disorder, affective psychoses, and other psychoses) were randomly selected from a catchment of 1.1 million people as part of the Australian Study of Low Prevalence (Psychotic) Disorders. Women and men were compared with respect to their premorbid functioning, onset and course of illness, symptomatology, levels of disability and service utilization.

RESULTS

Results within diagnostic groupings confirm differences in how men and women experience and express their illness. Within each diagnostic group, women reported better premorbid functioning, a more benign illness course, lower levels of disability and better integration into the community than men. They were also less likely to have a chronic course of illness. There were no significant differences in age at onset. Differences between women across the diagnostic groups were more pronounced than differences between women and men within a diagnostic group. In particular, women with schizophrenia were severely disabled compared to other women.

CONCLUSIONS

These comparisons across diagnostic groupings are among the most systematic and comprehensive in the literature. It is likely that several mechanisms are needed to explain the differences. Greater social integration and functioning in women across diagnostic groups may well reflect culturally and socially determined gender differences. In contrast, variability and attenuated findings with respect to symptom profiles beg the question of biological mechanisms with some degree of specificity.

A multivariate electrophysiological endophenotype, from a unitary cohort, shows greater research utility than any single feature in the Western Australian family study of schizophrenia

BACKGROUND

Previous studies have found several electrophysiological endophenotypes that each co-varies individually with schizophrenia. This study extends these investigations to compare and contrast four electrophysiological endophenotype, mismatch negativity, P50, P300, and antisaccades, and analyze their covariance on the basis of a single cohort tested with all paradigms. We report a multivariate endophenotype that is maximally associated with diagnosis and evaluate this new endophenotype with respect to its application to genetic analysis.

METHODS

Group differences and covariance were analyzed for probands (n = 60), family members (n = 53), and control subjects (n = 44). Associations between individual endophenotypes and diagnostic groups, as well as between the multivariate endophenotype and diagnostic groups, were investigated with logistic regression.

RESULTS

Results from all four individual endophenotypes replicated previous findings of deficits in the proband group. The P50 and P300 endophenotypes similarly replicated significant deficits in the family member group, whereas mismatch negativity and antisaccade measures showed a trend. There was minimal correlation between the different endophenotypes. A logistic regression model based on all four features significantly represented the diagnostic grouping (chi(2) = 32.7; p < .001), with 80% accuracy in predicting group membership.

CONCLUSIONS

A multivariate endophenotype, based on a weighted combination of electrophysiological features, provides greater diagnostic classification power than any single endophenotype.

The epidemiology of bipolar disorder: sociodemographic, disability and service utilization data from the Australian National Study of Low Prevalence (Psychotic) Disorders

OBJECTIVES

Data from the Australian National Study of Low Prevalence (Psychotic) Disorders were used to describe the clinical and sociodemographic profile of individuals with bipolar disorder, their levels of impairment and disability, and use of medication and treatment services.

METHODS

A 1-month census of contacts with mental health services, private psychiatric and general practices, as well as contact points in marginalized settings, was conducted in a national catchment of 1.1 million adults. The census yielded 3,800 individuals who screened positive for psychosis, of whom a random sample of 980 were administered a comprehensive semi-structured interview schedule. Results are presented on 112 persons with an ICD-10 diagnosis of bipolar disorder.

RESULTS

Overall, 69.6% of the 112 persons who met the ICD-10 criteria for bipolar disorder reported a recurrent episodic illness, 25.0% had a chronic course without clear remissions, and 5.4% had a single episode of mania. Assessed on a lifetime basis, suicidal ideation was common (78.6%) and levels of drug and alcohol abuse/dependence were high (32.1%). The majority (84.8%) had had at least one contact with inpatient, outpatient or emergency services in the previous year. Those with serious impairment had levels of service utilization similar to the rest of the sample, but were more likely to report a poorer quality of life and unmet service needs. While the percentage experiencing social and occupational dysfunction was substantial and similar for both sexes, women appeared to be better integrated socially than men. Comparisons with schizophrenia patients within the same survey sample highlighted less chronic impairment but equal or greater utilization of services by bipolar patients.

CONCLUSIONS

Despite low levels of chronicity, the burden of social disablement associated with bipolar disorder is high. The data suggest a number of important gaps in the provision of services for this predominantly treated population.

Pregnancy, delivery, and neonatal complications in a population cohort of women with schizophrenia and major affective disorders

OBJECTIVE

This study ascertained the incidence of complications during pregnancy, labor, and delivery and the neonatal characteristics of infants born to women with schizophrenia, bipolar disorder, or major depression in a population-based cohort.

METHOD

Based on records linkage across a psychiatric case register and prospectively recorded obstetric data, the study comprised women with schizophrenia or major affective disorders who had given birth to 3,174 children during 1980-1992 in Western Australia. A comparison sample of 3,129 births to women without a psychiatric diagnosis was randomly selected from women giving birth during 1980-1992. Complications were scored with the McNeil-Sjöström Scale. Odds ratios were calculated for specific reproductive events.

RESULTS

Both schizophrenic and affective disorder patients had increased risks of pregnancy, birth, and neonatal complications, including placental abnormalities, antepartum hemorrhages, and fetal distress. Women with schizophrenia were significantly more likely to have placental abruption, to give birth to infants in the lowest weight/growth population decile, and to have children with cardiovascular congenital anomalies. Neonatal complications were significantly more likely to occur in winter; low birth weight peaked in spring. Complications other than low birth weight and congenital anomalies were higher in pregnancies after psychiatric illness than in pregnancies preceding the diagnosis.

CONCLUSIONS

While genetic liability and gene-environment interactions may account for some outcomes, maternal risk factors and biological and behavioral concomitants of severe mental illness appear to be major determinants of increases in reproductive pathology in this cohort. Risk reduction in these vulnerable groups may be achievable through antenatal and postnatal interventions.

Linkage analysis in bipolar pedigrees adds support for a susceptibility locus on 21q22

Several studies provide suggestive evidence of a susceptibility locus for bipolar disorder at chromosome 21q22-23. In an attempt to replicate these findings, we have analyzed linkage to 11 polymorphic markers from this region in 18 Bulgarian pedigrees with affective disorder. Two-point linkage analysis under assumption of homogeneity and a dominant model with reduced penetrance produced modest positive values for some of the markers tested under a 'narrow' phenotype definition, including bipolar I and II, and schizoaffective disorder. The maximum two-point score (lod=1.76, theta=0.00) was at marker D21S1919. Non-parametric linkage analysis under the same phenotype model, yielded positive NPLall values (P<0.05) over the region between markers D21S211 and D21S416, with a peak at D21S1252 (NPL Zall=2.32, P=0.0003). The multipoint lod score (GENEHUNTER) reached a suggestive value for linkage (lod=2.10) also at marker D21S1252. The results under a recessive model were completely negative. These data add to the evidence for the existence of a susceptibility locus for bipolar affective disorder on chromosome 21q22.

Differential impairment of working memory performance in first-degree relatives of individuals with schizophrenia

BACKGROUND

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.

OBJECTIVE

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).

METHODS

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.

RESULTS

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.

CONCLUSIONS

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.

Association between reduced duration mismatch negativity (MMN) and raised temporal discrimination thresholds in schizophrenia

OBJECTIVE

The event-related potential known as mismatch negativity (MMN) is elicited whenever the auditory system detects a change against an invariant background of stimulation. A reduction in mismatch negativity is well established in schizophrenia. The present study explored the association between reduced duration mismatch negativity in schizophrenia and behavioural measures of temporal discrimination.

METHOD

Mismatch negativity amplitude to duration increments (125 vs. 50 ms) was compared between individuals with schizophrenia and healthy controls. Mismatch negativity amplitude was also related to two behavioural measures of temporal discrimination (silent and filled intervals) for detecting changes in stimuli of similar duration.

RESULTS

Patients produced higher discrimination threshold estimates and smaller amplitude mismatch negativity responses to temporally deviant stimuli. Temporal discrimination thresholds correlated with the amplitude of the phase reversal in mismatch negativity at the left mastoid such that patients who produced the highest thresholds produced the smallest mismatch response.

CONCLUSIONS

Imprecise representations of the temporal properties of auditory stimuli can account for some of the reduction in mismatch negativity amplitude in some patients but additional factors clearly contribute. The results suggest that patients who do and do not exhibit temporal processing deficits on behavioural tasks produce different patterns of reduction in duration mismatch negativity.

Death rate from ischaemic heart disease in Western Australian psychiatric patients 1980-1998

BACKGROUND

People with mental illness suffer excess mortality due to physical illnesses.

AIMS

To investigate the association between mental illness and ischaemic heart disease (IHD) hospital admissions, revascularisation procedures and deaths.

METHOD

A population-based record-linkage study of 210 129 users of mental health services in Western Australia during 1980-1998. IHD mortality rates, hospital admission rates and rates of revascularisation procedures were compared with those of the general population.

RESULTS

IHD (not suicide) was the major cause of excess mortality in psychiatric patients. In contrast to the rate in the general population, the IHS mortality rate in psychiatric patients did not diminish over time. There was little difference in hospital admission rates for IHD between psychiatric patients and the general community, but much lower rates of revascularisation procedures with psychiatric patients, particularly in people with psychoses.

CONCLUSIONS

People with mental illness do not receive an equitable level of intervention for IHD. More attention to their general medical care is needed.

Duration mismatch negativity in biological relatives of patients with schizophrenia spectrum disorders

BACKGROUND

One of the most consistent findings in schizophrenia research over the past decade is a reduction in the amplitude of an auditory event-related brain potential known as mismatch negativity (MMN), which is generated whenever a deviant sound occurs in a background of repetitive auditory stimulation. The reduced amplitude of MMN in schizophrenia was first observed for deviant sounds that differ in duration relative to background standard sounds, and similar findings have been observed for sounds that are deviant in frequency. The aim of this study was to determine whether first-degree relatives of schizophrenia patients show a similar reduction in MMN amplitude to duration deviants.

METHODS

We measured MMN to duration increments (deviants 100 msec vs. standards 50 msec) in 22 medicated patients with a diagnosis in the schizophrenia spectrum, 17 individuals who were first-degree unaffected relatives of patients, and 21 healthy control subjects.

RESULTS

Mismatch negativity amplitude was reduced in patients and relatives compared with control subjects. There were no significant differences between patients and relatives. In contrast, the subsequent positive component, P3a, was larger in relatives compared with patients.

CONCLUSIONS

These findings suggest that a reduced MMN amplitude may be an endophenotype marker of the predisposition to schizophrenia.

Do loudness cues contribute to duration mismatch negativity reduction in schizophrenia?

The present study explored duration mismatch negativity (MMN) reduction in schizophrenia. Duration MMN studies usually employ tones of very short duration (< 200 ms). For stimuli < 200 ms in duration, an increment in duration is accompanied by an increase in perceived loudness. It was previously proposed that the effectiveness of duration MMN in revealing MMN reduction in schizophrenia might be explained by patients being insensitive to loudness cues and duration increments. In this study we equated loudness cues in a typical duration MMN paradigm and explored the effect of this manipulation on MMN amplitude reduction in schizophrenia. The manipulation had little effect on a healthy comparison group but had a marked effect on the MMN generated in the patient group who produced a significantly smaller MMN response to the regular duration deviant than to that in the equated loudness condition. This result was interpreted as demonstrating that patients exhibit a very marked insensitivity to duration increments.

Increasing rates of suicide in Western Australian psychiatric patients: a record linkage study

OBJECTIVE

To investigate the risk of suicide following contact with mental health services and whether it has changed over time.

METHOD

Record linkage was used to obtain the records of previous hospital admissions and mental health service contacts for deaths due to suicide in the period 1980-98. Standardized incidence rates were calculated for the general population and for users of mental health services. Proportional hazards regression was used to assess risk factors within the cohort of people with mental health service contact.

RESULTS

Suicide risk was significantly increased in users of mental health services (rate ratio 6.66 in males and 7.52 in females). Suicide risk was highest in the first 7 days after discharge from in-patient care, and decreased exponentially with time since discharge. Suicide risk in users of mental health services has increased over the study period.

CONCLUSION

These results highlight the importance of adequate follow-up of patients discharged from in-patient services, and the need for adequate resources for community-based services.

Season of birth in schizophrenia and affective psychoses in Western Australia 1916-61

OBJECTIVE

This study examines seasonality birth effects in schizophrenia and affective psychoses in the southern hemisphere, given possible confounding of age-incidence effects with winter birth peaks in northern hemisphere data.

METHOD

Distributions of births by season, quarter and month for individuals born in Western Australia 1916-61 with a diagnosis of schizophrenia (N=2284), affective psychoses (N=3236), and neurotic depression (N=4869) on the statewide mental health register were compared with distributions for the general population.

RESULTS

We found no association between season of birth and schizophrenia, affective psychoses or neurotic depression. For schizophrenia, the pattern of risks by quarter reflects northern hemisphere trends. Results by month are difficult to interpret due to large fluctuations in the data. While age-incidence effects had no impact on the distribution of risk, we found an artefactual increase in January births due to routine imputation of missing birth dates.

CONCLUSION

Adjusting for artefacts in the data produced a pattern analogous to northern hemisphere trends.

Auditory sensory memory in schizophrenia: inadequate trace formation?

This study explored duration mismatch negativity reductions observed in individuals with schizophrenia, in particular, the relationship to behavioural measures of temporal discrimination and two event-related potential (ERP) components occurring during the first phase of auditory sensory memory. Twenty-two patients with a DSM-IV and ICD-10 diagnosis of schizophrenia and 25 healthy comparison volunteers participated in a behavioural and an ERP testing session. Both groups performed equivalently on behavioural estimates of filled interval duration discrimination and gap detection. In contrast, electrophysiological measures revealed a significant reduction in patients' duration mismatch negativity and a significant difference in patients for the pattern of N100 facilitation over short stimulus onset asynchronies. Whilst behavioural results indicate intact temporal processing of filled intervals and equal temporal resolution limits in schizophrenia, both ERP measures indicated differences in auditory processing that may be traced to activity occurring during the first 250 ms. Results highlight the possibility of abnormalities in the process of auditory trace formation and temporal summation in schizophrenia.

Mortality in Western Australian psychiatric patients

BACKGROUND

The aim was to examine mortality in psychiatric patients in Western Australia (WA), over a time period of considerable change in the delivery of mental health services.

METHODS

A population-based record linkage analysis was undertaken to quantify mortality among people with mental illness in WA. Mortality rates were calculated in users of mental health services and compared with rates in the whole population of WA. Trends in mortality were also examined using relative survival analysis, and proportional hazards regression.

RESULTS

The overall mortality rate ratio was 2.57 in males (95% CI: 2.51-2.64), and 2.18 in females (2.12-2.24). The highest cause-specific mortality rate ratio was for deaths due to suicide [RR: 7.37 in males (95% CI: 6.74-8.05) and 8.38 in females (95% CI: 7.11-9.89)], with mortality rate ratios being significantly greater than 1 for all other major causes of death. A relative survival analysis found that the excess mortality risk was concentrated in the first few years after first contact with mental health services. Proportional hazards regression analysis found a slight elevation of mortality rates over time.

CONCLUSIONS

Mortality among psychiatric patients remains high and appears to be increasing. Highest excess mortality rate is associated with suicide, but mortality rates are significantly elevated for all major causes of death.

Suicide and attempted suicide among older adults in Western Australia

BACKGROUND

Suicide rates are high in later life. Risk factors include male sex and depressive illness. This study investigated the relationship between suicidal behaviour and contact with mental health services among the elderly in Western Australia.

METHODS

Record linkage was used to obtain records of hospital admissions and mental health service contacts for all suicide attempts and deaths in the period 1980-95. Standardized incidence ratios were calculated for the elderly, general population and people with mental health service contacts. Cox regression was used to evaluated potential risk factors for elderly people who were in contact with mental health services.

RESULTS

People over 60 years of age accounted for 15% of suicides and 4.6% of attempted suicides. Suicide rates were 3.3 times higher in males and 4.4 times higher in females when compared to the general population of elderly people. For attempted suicide, the rate was 5.8 times higher in males and 6.6 times higher in females with prior contact with mental health services. Highest risk of suicide was found in patients with diagnoses of affective psychoses (RR = 3.7), adjustment reaction (RR = 3.2) or depressive disorder (RR = 2.8). The diagnosis of cancer was associated with decreased risk of suicide (RR = 3.6) and attempted suicide (RR = 1.9).

CONCLUSIONS

Suicide rates are high among the elderly in Western Australia. Suicide is significantly associated with the diagnosis of mood disorder. Suicide attempts are less common, and are associated most strongly with mood and personality disorders. The decreased risk of self-harm behaviour among patients with cancer warrants further investigation.

Duration and frequency mismatch negativity in schizophrenia

OBJECTIVES

The aim of the present study was to elucidate the reasons for apparent inconsistencies in the schizophrenia literature with respect to the mismatch negativity (MMN) waveform of the event-related potential (ERP). While most previous research has shown that MMN is reduced in schizophrenia, there are a small number of studies reporting that frequency MMN is not reduced.

METHODS

We recorded ERPs to auditory stimuli with different frequencies and durations from patients with schizophrenia (N = 14) and control subjects (N = 17) of similar age and sex. MMNs to small but discriminable frequency deviants were contrasted with large frequency deviants and duration deviants.

RESULTS

Only the MMN to duration deviants was significantly reduced in patients, although there was evidence of a similar trend for large frequency deviants.

CONCLUSIONS

The results together with a review of the frequency MMN literature suggest that there are 3 variables which are important in determining whether patients exhibit a reduced MMN to frequency deviants: deviant probability, degree of deviance and interstimulus interval. The results also indicated that patients with schizophrenia may have particular deficits in processing the temporal properties of auditory stimuli. This finding has implications for the pathophysiology of the disorder as time-dependent processing is reliant on the integrity of an extensive network of brain areas consisting of auditory cortex, areas of pre-frontal cortex, the basal ganglia and cerebellum.

Excess cancer mortality in Western Australian psychiatric patients due to higher case fatality rates

OBJECTIVE

To investigate the association between mental illness and cancer incidence, mortality and case fatality.

METHOD

A population-based record linkage study was undertaken based on 172,932 patients of mental health services in Western Australia. Records of mental health service contacts were linked with cancer registrations and death records.

RESULTS

While there was little difference in overall cancer incidence rates between psychiatric patients and the general community (RR in males 1.05, 95%, CI 1.02-1.09, RR in females 1.02, 0.98-1.05), cancer mortality was 39%, higher in males (95%) CI: 32-46%) and 24% higher in females (17-32%).

CONCLUSION

People with mental illness in Western Australia do not show an increased incidence rate of cancer, but do have higher cancer mortality. This was attributed to a higher cancer case fatality rate among people with mental illness.

Suicide rates in psychiatric in-patients: an application of record linkage to mental health research

OBJECTIVE

To study trends in the rate of suicide in psychiatric patients in Western Australia. To examine the associations of suicide with demographic and clinical factors.

METHODS

A population-based cohort of 52,010 individuals whose first psychiatric admission occurred in 1980-95 was identified from the Health Services Research Linked Database. There were 471 deaths by suicide by 31 December 1995. Age standardised suicide rates per 1,000 person-years at risk were calculated. Suicide rates in the first year after a patient's first admission were also examined and a proportional hazards regression analysis was performed to examine risk factors for suicide.

RESULTS

Male psychiatric patients were 3.4 times more likely to commit suicide than female patients (95% CI 2.76-4.24). Younger patients were at higher risk than older patients, and patients with extended periods of in-patient treatment were at more than double the risk of short-stay patients. Over the 16-year period, the rate of suicide in the first year after first psychiatric admission was found to increase by 3.4% a year (95% CI -0.7-7.6%).

CONCLUSIONS

The findings confirm that psychiatric patients are at high risk of suicide. Patient outcomes in terms of risk of suicide after hospital discharge have deteriorated.

IMPLICATIONS

Improvements are needed in the provision of community support to high risk psychiatric patients. Further work should be done to identify patients at highest risk of suicide.