Cohort Profile Update: The New South Wales Child Development Study (NSW-CDS) – Wave 3 (child age ∼18 years)

Abstract

The New South Wales Child Development Study (NSW-CDS) was established to enable an intergenerational life-course approach to identifying risk and protective factors for adolescent-onset mental health problems in an Australian state-based population cohort. New multi-agency linked administrative data for the child cohort (n = 91 597 children; 44 216 female) now span birth to ∼18 years (including birth, mortality, health, education, child protection, criminal justice and welfare records up to 2021/2022), with parental data obtained for ∼83% of the child cohort via births registered in NSW or perinatal records in NSW or the Australian Capital Territory. Attrition is limited to deaths and movement out of the jurisdictions of various record sources (e.g. state government or Australian Commonwealth). The added range of adolescent data provides new targets for investigation of outcomes in relation to developmental vulnerability at school entry (age 5–6 years; 2009 Australian Early Development Census), and mental health and wellbeing assessed via self-report survey in Year 6 (age 11–12 years; 2015 Middle Childhood Survey). Australian government data are governed by privacy laws that prohibit data sharing. To discuss potential collaborative projects, please contact Melissa Green. The New South Wales Child Development Study (NSW-CDS) was originally established with 87 037 children assessed with the Australian Early Development Census (AEDC) when they started school in NSW in 2009 (aged 5–6 years); in 2013, children’s AEDC records were linked to birth, mortality, health, education, child protection and criminal justice records for the children and their parents1 using probabilistic record linkage [www.cherel.org.au/]. In subsequent years, the cohort was expanded to include 27 792 children who participated in the self-report Middle Childhood Survey (MCS)2 administered in Year 6 (age 11–12 years), bringing the total child cohort to 91 635 for the Wave 2 linkage in 2016, for whom parent data linkage was available for 82.0%.3 Findings from these data are relevant to public policy responses at the intersection of child mental health,4–7 maternal-child health,8–10 child protection services,11–14 youth justice15,16 and school-based mental health and wellbeing.17 Children in the NSW-CDS cohort have matured into late adolescence, the peak age for mental illness onset. All records in the original record linkages have thus been updated to the child’s age 17–18 years (the majority to 2021) in this third wave of linkage. We additionally convened new health data from the Australian Capital Territory (ACT) to improve the coverage of health service contacts (including perinatal data) for families living on the border of NSW and the ACT. New Commonwealth records from the Australian Institute of Health and Welfare and Department of Social Services have also been added to improve mental health service coverage beyond hospital and ambulatory services, and to derive indices of individual-level socioeconomic status, respectively. Additionally, to enhance the detail with which risk and protective factors are captured in linked records, new state government records have been obtained, including records of children with registered disability in public schools, child protection records for the parent cohort, and criminal justice data extending to police cautions and youth justice conferences. Linked administrative records are detailed in Table 1. Multi-agency data collections in the New South Wales (NSW) Child Development Study (1971–2022): record linkage rates for child and parent cohorts ACT, Australian Capital Territory; BOCSAR, Bureau of Crime Statistics and Research; CODURF, Cause of Death Unit Record File; DCJ, Department of Communities and Justice; DOMINO, Data Over Multiple Individual Occurrences; MHOAT, Mental Health Outcomes and Assessment Toolkit; NAPLAN, National Assessment Program—Literacy and Numeracy; n/a, not applicable because there were more records received than individuals (i.e. duplicate or mislinked records), such that a percentage of the source population for whom records were linked by third-party linkage agencies (linkage rate) could not be calculated. New records accessed for the first time in Wave 3 linkage. Admissions include birth-related hospitalizations. New data linkages provide enhanced capacity for unique epidemiological surveillance of life-course risk for mental disorders emerging in adolescence, including self-harm and suicidal ideation, and other related educational, justice and social outcomes. Access to child protection records for the parent cohort allows greater depth of study of intergenerational trauma, and the addition of Commonwealth health records enhance the capacity for understanding barriers to accessing public health care for mental health problems. These data will support longitudinal population research to inform policy to prevent suicide and the development of chronic mental disorder in young people. The NSW-CDS (Wave 3 Linkage) cohort comprises 91 597 children (44 216 female) who were assessed with the 2009 AEDC (n = 87 014; 95%) and/or the 2015 MCS (n = 27 792; 30.3%); notably, 25.3% (n = 23 209) of children were assessed with both the AEDC and the MCS, and 5.0% (n = 4583) of children completed the MCS only. Updated record linkage algorithms retained most of the children (99.9% of 91 635 children) from the previous Wave 2 linkage conducted in 2016. As of 31 December 2021, 72.5% (n = 66 420) of the Wave 3 child cohort were aged 18 years and 25.0% (n = 22 923) were aged 17 years (age range = 15.2–20.6 years). Parent data were obtained for 82.7% (n = 75 784) children with birth registration records available in the NSW Registry of Births, Deaths and Marriages or the NSW and ACT Perinatal data collections. Mother records were available for 82.7% (n = 75 784) children (representing 74 519 unique mothers), and father records were available for 82.2% (n = 75 332) children (representing 74 042 unique fathers). The undertaking of new linkages (to 2021/22) for the NSW-CDS cohorts has served to increase the information available in some of the originally linked records and, importantly, extended the age range of the children into late adolescence. Alongside the additional linkage of new Commonwealth Health and Welfare data and ACT Health records, the new linkages have enhanced the measurement of all aspects of health, educational, criminal and child protection information for both the child and parent cohorts. We provide updated summary data for these key pillars of measurement to showcase the noticeable increases in prevalence of school exclusions, mental health problems and justice contacts among the children, and child protection contacts (in particular) for parent cohorts. The NSW-CDS Wave 3 linkage comprises updated data for all records originally linked for the child and parent cohorts (Table 1), including new information on: birth and mortality data in the NSW Registry of Births, Deaths and Marriages, and Cause of Death data from the Australian Coordinating Registry; new education data for the child cohort, including secondary school Student Enrolment and Suspension and Expulsion records and primary and secondary school Targeted Specialist Support Services records from the NSW Department of Education (government schools only), as well as two new grade levels for the National Assessment Program—Literacy and Numeracy tests (NAPLAN; now spanning Years 3, 5, 7, 9), from the NSW Education Standards Authority on behalf of the Australian Curriculum, Assessment and Reporting Authority (government and non-government schools); new parental child protection and out-of-home care records from the NSW Department of Communities and Justice; new health records from NSW and ACT Health’s Perinatal, Emergency Department Data Collection, Admitted Patients Data Collection, the NSW Mental Health Ambulatory, Mental Health Outcomes and Assessment Toolkit and Controlled Drugs Data Collection data collections, and from the Commonwealth Medical Benefits Schedule and Pharmaceutical Benefits Scheme; criminal justice records from the NSW Bureau of Crime Statistics and Research (BOCSAR) Reoffending and Custody databases and police contact data (for the child cohort) from the NSW Police Force Computerised Operational Policing System (COPS); and family welfare data from the Commonwealth Department of Social Services. Table 1 provides the years available for each record set and the number of child and parents identified in each collection. Demographic characteristics are presented in Table 2 for various sub-cohorts of children upon which future studies will be based, according to data availability. Postcode of residence was used to determine both area-based socioeconomic disadvantage according to the Socio-Economic Indexes for Areas (SEIFA) Index of Relative Socioeconomic Disadvantage18 and remoteness according to the Australian Statistical Geography Standard Remoteness Areas.19 Demographic characteristics of child sub-cohorts within the New South Wales Child Development Study Wave 3 Linkage AEDC, Australian Early Development Census; ARIA, Accessibility and Remoteness Index of Australia; IRSD, Index of Relative Socio-economic Disadvantage; MCS, Middle Childhood Survey; SEIFA, Socio-Economic Indexes for Areas. For completeness, Table 3 provides a summary of children rated as developmentally vulnerable on the original 2009 AEDC,20 alongside selected characteristics from new data available for the child cohort on academic achievement (2011–19), school exclusions (2012–22), school services for disability (2012–18), mental disorder diagnoses (2001–21), criminal justice contacts (2010–22) and child protection involvement (2001–20). Selected characteristics of the New South Wales (NSW) Child Development Study child sub-cohort/s according to available records in each set AEDC, Australian Early Development Census; APDC, NSW and Australian Capital Territory (ACT) Admitted Patients Data Collections; BOCSAR, Bureau of Crime Statistics and Research; COPS, Computerised Operational Policing System; EDDC, NSW and ACT Emergency Department Data Collections; MH-AMB, Mental Health Ambulatory Data; NAPLAN, National Assessment Program Literacy and Numeracy; TSSS, Targeted Specialist Support Services. NAPLAN denominators are the number of children with complete data on all five NAPLAN domains in that year. The BOCSAR Re-Offending Database includes information on all court appearances and outcomes for finalized criminal charges for individuals convicted of at least one proven offence between 1994 and 2022, and all non-court outcomes (i.e. police cautions and youth justice conference diversionary measures) from 1998 to 2022 for persons with or without a proven offence, as well as separate data on custody periods (including remand) with discharge date between 2000 and 2022 for persons with or without a proven offence. Incarceration events were harmonized across BOCSAR Reoffending and Custody data sets. Reported issues that meet the ‘Risk of Significant Harm’ threshold are not necessarily substantiated, unless specified. Early childhood developmental vulnerability was assessed in 2009 with the teacher-rated, 104-item AEDC, scored on five domains (social competencies, emotional maturity, physical health and wellbeing, language and cognitive skills [school-based], and communication skills and general knowledge).20 Children falling below the 10th centile of the 2009 national distribution are categorically classified as developmentally ‘vulnerable’; children in the 10th–25th centile are classified as developmentally ‘at risk’; and all other children >25th centile are classified as developmentally ‘on track’. Academic achievement in middle childhood was indexed via attainment of national minimum standard for age on all five domains of the NAPLAN at each year-level of assessment (Years 3, 5 7, 9; typically ages ∼8, ∼10, ∼12, ∼14 years). At least one NAPLAN assessment was available for 93.6% (n = 85 712) of the total child cohort, and all four NAPLAN assessment points for 76.5% (n = 70 070) children in the cohort. School suspensions and expulsions were recorded for children enrolled in NSW government schools between Year 3 and Year 12; school enrolment records were available for kindergarten through Year 12. School services for disability were recorded in Targeted Specialist Support Services data available at four census points (August 2012, 2014, 2016 and 2018) for children with impediments to learning and/or disability enrolled in NSW government schools; the proportion of children with a verified disability who received support, those receiving ‘integrated funding support’ within a mainstream class and/or those placed in a specialist support class are reported in Table 3. Mental disorder diagnoses were determined for child (Table 3) and parents (Table 4) according to Chapter V (F00-F99) ICD-10-AM diagnostic codes in NSW and ACT Emergency Department Data Collection, Admitted Patients Data Collection and the NSW Mental Health Ambulatory data collections spanning 2001–21. The numbers of children and parents with specific health conditions and/or mental disorder diagnoses, derived across all health records, are reported in Supplementary Tables S1–S3 (available as Supplementary data at IJE online), respectively. Selected characteristics of the New South Wales (NSW) Child Development Study parent sub-cohorts ACT, Australian Capital Territory; BOCSAR, Bureau of Crime Statistics and Research. Incarceration counts were harmonized for individuals across BOCSAR charges and custody datasets. Reported issues that meet the ‘Risk of significant harm’ threshold are not necessarily substantiated, unless specified. Intentional self-harm encompassed death by hanging, strangulation and/or suffocation. Criminal justice contacts from the BOCSAR included information for child and parent cohorts from the Re-Offending Database, covering all court appearances and outcomes (including custody, fines, community service etc) for finalized criminal charges for individuals convicted of at least one proven offence between 1994–2022, and all non-court outcomes (i.e. police cautions and youth justice conference diversionary measures) from 1998–2022 for persons with or without a proven offence, as well as separate data on custody periods (including remand) with discharge date between 2000–22 for persons with or without a proven offence. The numbers of children and parents with specific types of offences are presented in Tables 3 and 4, respectively, and additional information about the numbers of children and parents with criminal and non-court outcomes, and certain types of offences according to the Australian and New Zealand Standard Offence Classification system, are presented in Supplementary Tables S4 and S5 (available as Supplementary data at IJE online), respectively. In addition, COPS data (2000–21) were obtained for the child cohort (Table 3), containing records of all events reported to, or detected by, the NSW Police Force for all criminal and non-criminal incidents, but does not include other contact relating to ‘children at-risk’ (e.g. where risk of harm has been mandatorily reported to the Police), or other positive police contacts. Police contacts are recorded as either a: (i) victim—a person who suffers harm as a direct result of an act committed during a criminal offence (not limited to violence); (ii) witness—a person who saw, heard or experienced something related to a criminal offence; or (iii) person of interest—an individual who has not necessarily been arrested or formally accused of a crime but is of interest to the police during their investigation. Child protection reports and out-of-home care data were available for both child (2001–20) and parent (1971–2020) cohorts in records from the NSW Department of Communities and Justice’s ChildStory data, including referrals for various family preservation programmes. We report indices relating to periods of placement in out-of-home care, any substantiated or non-substantiated Risk of Significant Harm report (meeting threshold of risk for follow-up by caseworkers) and any non-Risk of Significant Harm report, as well as involvement in various support services (e.g. Brighter Futures, Intensive Family Support Services), or assessment during placement transition with the Child Assessment Toolkit (Table 3). Among the parent cohort, 7.5% of mothers and 3.1% of fathers had historical (childhood) contact with NSW child protection services (Table 4). Among the 23 467 children in the cohort with linked parental data and at least one child protection report or out-of-home care placement, 15.4% (n = 3621) had at least one parent with their own prior child protection contact in NSW, and 1.9% (n = 459) of children were born to parents who had both been in receipt of NSW child protection services. The Medical Benefits Schedule (Child: 2002–18; Parents: 1984–2018) provides a record of the medical services for which the Australian Government pays a rebate via the universal health care system known as Medicare. The numbers of children and parents with selected services,, including General Practitioner Attendance (accounting for >99% of all Medicare users), any Psychologist or Psychiatrist Attendance, or other mental health intervention, are presented in Table 5. Details regarding the specific Medicare items included in these categories are provided in Supplementary Table S6 (available as Supplementary data at IJE online). Numbers of children and parents with selected Medicare Benefits Schedule, Pharmaceutical Benefits Scheme and welfare payments DOMINO, Data Over Multiple Individual Occurrences. The Pharmaceutical Benefits Scheme (2001–19) forms part of the Australian Government’s broader National Medicines Policy to subsidise the cost of medicines. These data therefore reflect dispensed prescriptions for medicines covered under the scheme but do not guarantee that the medicine has been taken by the recipient. The numbers of children, mothers and fathers prescribed Anti-infective or Nervous System drugs, according to the World Health Organization’s Anatomical Therapeutic Chemical Classification, are presented in Table 5. Data Over Multiple Individual Occurrences records provide information about family welfare payments from 2002–18. Table 5 presents the numbers of children and parents receiving ‘any welfare benefit’ including those considered near universal for families with children (e.g. Family Tax Benefit), and those receiving a ‘means-tested welfare benefit’ (in which benefit eligibility was subject to an income and assets test aimed at assisting those experiencing financial hardship; see details in Supplementary Table S7, available as Supplementary data at IJE online). Key findings are updated regularly on the study website [https://www.unsw.edu.au/research/nsw-cds]. New findings have demonstrated high rates of self-harm and suicidal ideation among children known to child protections services—particularly those placed in out-of-home care.21 We have also determined that, among all human service agencies, risk for self-harm or suicide is most commonly recorded in child protection records, at the earliest age, with a smaller proportion of cases identified in health records in later adolescence.22 We have developed childhood, population-level indicators of risk for adolescent mental disorders,23 based on patterns of psychopathology in middle childhood.24 Psychometrically robust measures of school-based social-emotional learning competencies have also been developed for in the of school mental health and wellbeing and in relation to other Relative of the study include the of two of the child cohort with administrative data using record linkage which and and to administrative data are not typically for research and potential in data entry or are beyond but are to be with in a of this data in administrative record collections that to risk and protective factors for mental health problems not be of data include the of data for some children births were not registered in the state of NSW (i.e. born or in or for whom or identifying information was available in the birth registration and placed on the of multi-agency linked government data to these contact the first with their of was provided by the NSW and Health Services and ACT Health Research and the Australian Institute of Health and Welfare Research with relevant data Linkage of data was conducted via of with the Australian National Health and Medical Research National of in with for data and of the Supplementary data are available at IJE the of the research and the and and data and conducted primary data and obtained funding to support the the all the of the research was conducted by the of New South Wales with financial support from the Australian Research Linkage with the NSW of NSW Department of and the NSW Department of Communities and the Linkage to and Early to and the National Health and Medical Research and and to research used population data by NSW Department of Australian Curriculum, Assessment and Reporting Authority by the NSW Education Standards NSW Department of Communities and Justice; NSW of ACT NSW Registry of Births, Deaths and the Australian Coordinating Registry behalf of Australian of Births, Deaths and Marriages, Australian and the National Australian Bureau of Australian Institute of Health and Department of Social NSW Bureau of Crime Statistics and Research; NSW Department of NSW Police research used data from the Australian Early Development Census The AEDC is by the Australian Government Department of The findings and reported are those of the and not be to these or the NSW and Australian

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