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Objective: The interplay between genetic and environmental factors on risk for psychotic illness remains poorly understood. The aim of this study was to estimate independent and combined effects of familial liability for schizophrenia and exposure to obstetric complications on risk for developing psychotic illness, covarying with exposure to other environmental stressors., Methods: This whole-population birth cohort study used record linkage across Western Australian statewide data collections (midwives, psychiatric, hospital admissions, child protection, mortality) to identify liveborn offspring ( n  = 1046) born 1980-1995 to mothers with schizophrenia, comparing them to offspring of mothers with no recorded psychiatric history ( n  = 298,370)., Results: Both maternal schizophrenia and pregnancy complications were each significantly associated with psychotic illness in offspring, with no interaction. Non-obstetric environmental stressors significantly associated with psychotic illness in offspring included the following: being Indigenous; having a mother who was not in a partnered relationship; episodes of disrupted parenting due to hospitalisation of mother, father or child; abuse in childhood; and living in areas of greatest socioeconomic disadvantage and with elevated rates of violent crime. Adjustment for these other environmental stressors reduced the hazard ratio for maternal schizophrenia substantially (from hazard ratio: 5.7, confidence interval: 4.5-7.2 to hazard ratio: 3.5, confidence interval: 2.8-4.4), but not the estimate for pregnancy complications (hazard ratio: 1.1, confidence interval: 1.0-1.2). The population attributable fraction for maternal schizophrenia was 1.4 and for pregnancy complications was 2.1., Conclusion: Our finding of a substantial decrease in risk of psychotic illness associated with familial liability for psychosis following adjustment for other environmental stressors highlights potentially modifiable risk factors on the trajectory to psychotic illness and suggests that interventions that reduce or manage exposure to these risks may be protective, despite a genetic liability.

Objective: Children of mothers with severe mental illness are at significantly increased risk of developing intellectual disability. Obstetric complications are also implicated in the risk for intellectual disability. Moreover, children of mothers with severe mental illness are more likely to be exposed to obstetric complications. The purpose of this study was to examine the independent and joint contributions of familial severe mental illness and obstetric complications to the risk of intellectual disability., Method: Record linkage across Western Australian whole-population psychiatric, inpatient, birth, and midwives' registers identified 15,351 children born between 1980 and 2001 to mothers with severe mental illness and 449,229 children born to mothers with no mental illness. Multivariable models were adjusted for paternal psychiatric status, parental intellectual disability, and other family and sociodemographic covariates., Results: The risk of intellectual disability was increased among children of mothers with severe mental illness compared with children of unaffected mothers. The impact varied across maternal diagnostic groups. For children of mothers with schizophrenia, the unadjusted odds ratio was 3.8 (95% CI=3.0, 4.9) and remained significant after simultaneous adjustment for exposure to obstetric complications and other covariates (odds ratio=1.7, 95% CI=1.3, 2.3). The odds ratio for exposure to obstetric complications also remained significant after adjustment (odds ratio=1.7, 95% CI=1.6, 1.8). For intellectual disability of a genetic basis, the adjusted odds ratio for maternal schizophrenia was elevated but not statistically significant. Among children with intellectual disability, 4.2% later developed a psychotic disorder, compared with 1.1% of children without intellectual disability., Conclusions: Maternal severe mental illness and exposure to obstetric complications contribute separately to the risk of intellectual disability, suggesting potentially different causal pathways.

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.

Twin registers have been established worldwide to study the roles of genes and the environment in health and behaviour. While questionnaire surveys are thought to be the most cost-effective way of collecting large amounts of data, low response rates can result in response bias. Many different strategies have been proposed to maximise response rates. A register of all multiple births occurring in Western Australia (WA) from 1980 onwards has been established using probabilistic record linkage techniques. Families who had not experienced the death of one or more of their multiples were invited to participate in the Western Australian Twin Child Health (WATCH) study, which studied the genetic and environmental determinants of childhood asthma and atopy. Several questionnaire designs and follow-up methods were assessed. We have shown that it was feasible to use a population-based register of multiple births to contact families for a questionnaire study. Questionnaire length, mode of follow-up, the number of responses required and the of participants all seemed to affect response.

This paper describes the creation of a unique maternal identifier for use in the investigation of perinatal, postneonatal and child outcomes in relation to maternal characteristics. All Midwives' records of Western Australian (WA) births were routinely linked to registrations of births and deaths for infants born from 1980 to 1992 inclusive, then linked to WA hospital discharge data and to registries of birth defects and cerebral palsy to create a longitudinal health record for each infant. However, since each birth to a woman was recorded as a separate event, there was no way to identify siblings. Probabilistic record linkage, based on information about the mother, was used for this task. Logical inconsistencies within the data were used to test the validity of the linkages between birth records attributed to each mother. Information about the mother from other epidemiological studies and data abstracted from hospital case notes was also used to validate sibships. Linkage of the records of 310,255 births in WA during that period resulted in the formation of 181,133 sibships of one or more children. Pooling the results of all of the validation methods gave an error of 0.9%. Linkage identified 3678 sibships containing multiple births, and 305 sets of maternal twins. Ascertainment of twins and their siblings for an ongoing twin register, the WA Twin Child Health (WATCH) study, was a natural consequence of this process.