Outcome risk model development for heterogeneity of treatment effect analyses: a comparison of non-parametric machine learning methods and semi-parametric statistical methods.

BACKGROUND: In randomized clinical trials, treatment effects may vary, and this possibility is referred to as heterogeneity of treatment effect (HTE). One way to quantify HTE is to partition participants into subgroups based on individual's risk of experiencing an outcome, then measuring treatment effect by subgroup. Given the limited availability of externally validated outcome risk prediction models, internal models (created using the same dataset in which heterogeneity of treatment analyses also will be performed) are commonly developed for subgroup identification. We aim to compare different methods for generating internally developed outcome risk prediction models for subject partitioning in HTE analysis. METHODS: Three approaches were selected for generating subgroups for the 2,441 participants from the United States enrolled in the ASPirin in Reducing Events in the Elderly (ASPREE) randomized controlled trial. An extant proportional hazards-based outcomes predictive risk model developed on the overall ASPREE cohort of 19,114 participants was identified and was used to partition United States' participants by risk of experiencing a composite outcome of death, dementia, or persistent physical disability. Next, two supervised non-parametric machine learning outcome classifiers, decision trees and random forests, were used to develop multivariable risk prediction models and partition participants into subgroups with varied risks of experiencing the composite outcome. Then, we assessed how the partitioning from the proportional hazard model compared to those generated by the machine learning models in an HTE analysis of the 5-year absolute risk reduction (ARR) and hazard ratio for aspirin vs. placebo in each subgroup. Cochran's Q test was used to detect if ARR varied significantly by subgroup. RESULTS: The proportional hazard model was used to generate 5 subgroups using the quintiles of the estimated risk scores; the decision tree model was used to generate 6 subgroups (6 automatically determined tree leaves); and the random forest model was used to generate 5 subgroups using the quintiles of the prediction probability as risk scores. Using the semi-parametric proportional hazards model, the ARR at 5 years was 15.1% (95% CI 4.0-26.3%) for participants with the highest 20% of predicted risk. Using the random forest model, the ARR at 5 years was 13.7% (95% CI 3.1-24.4%) for participants with the highest 20% of predicted risk. The highest outcome risk group in the decision tree model also exhibited a risk reduction, but the confidence interval was wider (5-year ARR = 17.0%, 95% CI= -5.4-39.4%). Cochran's Q test indicated ARR varied significantly only by subgroups created using the proportional hazards model. The hazard ratio for aspirin vs. placebo therapy did not significantly vary by subgroup in any of the models. The highest risk groups for the proportional hazards model and random forest model contained 230 participants each, while the highest risk group in the decision tree model contained 41 participants. CONCLUSIONS: The choice of technique for internally developed models for outcome risk subgroups influences HTE analyses. The rationale for the use of a particular subgroup determination model in HTE analyses needs to be explicitly defined based on desired levels of explainability (with features importance), uncertainty of prediction, chances of overfitting, and assumptions regarding the underlying data structure. Replication of these analyses using data from other mid-size clinical trials may help to establish guidance for selecting an outcomes risk prediction modelling technique for HTE analyses.

Long-term effects of a coalmine fire on hospital and ambulance use: An interrupted time series study.

BACKGROUND: In 2014, the Hazelwood coalmine fire in regional Victoria, Australia shrouded nearby communities in smoke for six weeks. Prior investigations identified substantial adverse effects, including increases in the use of health services. In this study, we examined the effects on hospital and ambulance use in the eight years following the fire. METHODS: Using Victorian hospital (Jan 2009-Jun 2022) and ambulance (Jan 2013-Dec 2021) data, we conducted an interrupted time series of changes to the rate of hospital admissions, emergency presentations, and ambulance attendances. A categorical exposure model compared two locations, most-exposed Morwell and less-exposed Latrobe Valley, to the rest of regional Victoria. A continuous exposure model used spatial estimates of fire-related PM2.5. Analyses were stratified by sex, age group (<65/65+ years), and condition (cardiovascular, respiratory, mental health, injury). RESULTS: There were small but significant increases in overall hospital admissions and emergency presentations across all analyses, but little evidence of change in overall ambulance attendances. Effects varied considerably by condition, with the biggest relative increases observed among hospital admissions for mental health conditions and injuries. While cardiovascular-related hospital admissions and emergency presentations increased post-fire, ambulance attendances decreased. CONCLUSIONS: Our findings suggest the Hazelwood coalmine fire likely increased hospital usage. However, it is unclear whether this was due to the direct effects of smoke exposure on health, or the disruptive socioeconomic and behavioural impacts of an environmental disaster that affected how communities engaged with various health services.

Does diet quality moderate the long-term effects of discrete but extreme PM2.5 exposure on respiratory symptoms? A study of the Hazelwood coalmine fire.

In 2014, a fire at an open cut coalmine in regional Victoria, Australia burned for 6 weeks. Residents of the nearby town of Morwell were exposed to smoke, which included high levels of fine particulate matter (PM2.5). We investigated whether the long-term effects of PM2.5 on respiratory health were moderated by diet quality. A cross-sectional analysis was conducted of data collected 8.5 years after the mine fire from 282 residents of Morwell and 166 residents from the nearby unexposed town of Sale. Primary outcomes were respiratory symptoms. Exposure was coalmine fire-related PM2.5 and diet quality was assessed as Australian Recommended Food Score (ARFS) derived using the Australian Eating Survey (AES). The moderating effect of diet quality on respiratory outcomes associated with PM2.5 was assessed using logistic regression models, adjusting for potential confounders. Diet quality was poor in this sample, with 60% in the lowest category of overall diet quality. Overall diet quality and fruit and vegetable quality significantly attenuated the association between PM2.5 and prevalence of chronic cough and phlegm. Sauce/condiment intake was associated with a greater effect of PM2.5 on COPD prevalence. No other moderating effects were significant. The moderating effects of overall diet quality and vegetable and fruit intake aligned with a priori hypotheses, suggesting potential protective benefits. While more evidence is needed to confirm these findings, improving diets, especially fruit and vegetable intake, may provide some protection against the effects of smoke exposure from fire events.

Advancing randomized controlled trial methodologies: The place of innovative trial design in eating disorders research.

Randomized controlled trials can be used to generate evidence on the efficacy and safety of new treatments in eating disorders research. Many of the trials previously conducted in this area have been deemed to be of low quality, in part due to a number of practical constraints. This article provides an overview of established and more innovative clinical trial designs, accompanied by pertinent examples, to highlight how design choices can enhance flexibility and improve efficiency of both resource allocation and participant involvement. Trial designs include individually randomized, cluster randomized, and designs with randomizations at multiple time points and/or addressing several research questions (master protocol studies). Design features include the use of adaptations and considerations for pragmatic or registry-based trials. The appropriate choice of trial design, together with rigorous trial conduct, reporting and analysis, can establish high-quality evidence to advance knowledge in the field. It is anticipated that this article will provide a broad and contemporary introduction to trial designs and will help researchers make informed trial design choices for improved testing of new interventions in eating disorders. PUBLIC SIGNIFICANCE: There is a paucity of high quality randomized controlled trials that have been conducted in eating disorders, highlighting the need to identify where efficiency gains in trial design may be possible to advance the eating disorder research field. We provide an overview of some key trial designs and features which may offer solutions to practical constraints and increase trial efficiency.

Long-term effects of extreme smoke exposure on COVID-19: A cohort study.

BACKGROUND: In 2014, the Hazelwood coalmine fire shrouded the regional Australian town of Morwell in smoke and ash for 6 weeks. One of the fire's by-products, PM2.5 , is associated with an increased risk of COVID-19 and severe disease. However, it is unclear whether the effect persisted for years after exposure. In this study, we surveyed a cohort established prior to the pandemic to determine whether PM2.5 from the coalmine fire increased long-term vulnerability to COVID-19 and severe disease. METHODS: From August to December 2022, 612 members of the Hazelwood Health Study's adult cohort, established in 2016/17, participated in a follow-up survey that included standardized items to capture COVID-19 cases, as well as questions about hospitalization and vaccinations. Associations were evaluated in crude and adjusted logistic regression models. RESULTS: A total of 268 (44%) participants self-reported or met symptom criteria for having had COVID-19 at least once. All models found a positive association, with odds of COVID-19 increasing by between 4% and 30% for a 10 µg/m3 increase in coalmine fire-related PM2.5 exposure. However, the association was significant in only 2 of the 18 models. There were insufficient hospitalizations to examine severity (n = 7; 1%). CONCLUSION: The findings are inconclusive on the effect of coalmine fire-related PM2.5 exposure on long-term vulnerability to COVID-19. Given the positive association that was robust to modelling variations as well as evidence for a causal mechanism, it would be prudent to treat PM2.5 from fire events as a long-term risk factor until more evidence accumulates.

Ventilation heterogeneity is increased in adults exposed to coal mine fire-related PM2.5.

BACKGROUND AND OBJECTIVES: The Hazelwood Health Study was set up to study long-term health effects of a mine fire that blanketed residents of the Latrobe Valley with smoke for 45 days in 2014. The Respiratory Stream specifically assessed the impact of fine particulate matter <2.5 µm diameter (PM2.5) exposure from mine fire smoke on lung health. The multiple breath nitrogen washout (MBW) test assesses ventilation heterogeneity, which may detect sub-clinical airways dysfunction not identified using standard tests such as spirometry. This analysis assessed the association of PM2.5 exposure with measures of ventilation heterogeneity. METHODS: Exposed (Morwell) and unexposed (Sale) participants were recruited 3.5-4 years after the fire from those who had participated in an Adult Survey. MBW was performed to measure lung clearance index (LCI), functional residual capacity (FRC), acinar (Sacin) and conductive (Scond) ventilation heterogeneity. PM2.5 exposure was estimated with emission and chemical transport models. Multivariable linear regression models were fitted controlling for confounders. RESULTS: We recruited 519 participants. MBW tests were conducted on 504 participants with 479 acceptable test results (40% male; 313 exposed, 166 unexposed). Exposure to mine fire-related PM2.5 was associated with increasing Scond (ß = 1.57/kL, 95%CI: 0.20-2.95, p = 0.025), which was comparable to the estimated effect on Scond of 4.7 years of aging. No other MBW outcomes were statistically different. CONCLUSION: Increasing exposure to PM2.5 was associated with increased ventilation heterogeneity in the conductive region of the lungs 4 years after the event.

Lung function changes in children exposed to mine fire smoke in infancy.

BACKGROUND AND OBJECTIVE: Chronic, low-intensity air pollution exposure has been consistently associated with reduced lung function throughout childhood. However, there is limited research regarding the implications of acute, high-intensity air pollution exposure. We aimed to determine whether there were any associations between early life exposure to such an episode and lung growth trajectories. METHODS: We conducted a prospective cohort study of children who lived in the vicinity of the Hazelwood coalmine fire. Lung function was measured using respiratory oscillometry. Z-scores were calculated for resistance (R5 ) and reactance at 5 Hz (X5 ) and area under the reactance curve (AX). Two sets of analyses were conducted: (i) linear regression to assess the cross-sectional relationship between post-natal exposure to mine fire-related particulate matter with an aerodynamic diameter of less than 2.5 micrometres (PM2.5 ) and lung function at the 7-year follow-up and (ii) linear mixed-effects models to determine whether there was any association between exposure and changes in lung function between the 3- and 7-year follow-ups. RESULTS: There were no associations between mine fire-related PM2.5 and any of the lung function measures, 7-years later. There were moderate improvements in X5 (ß: -0.37 [-0.64, -0.10] p = 0.009) and AX (ß: -0.40 [-0.72, -0.08] p = 0.014), between the 3- and 7-year follow-ups that were associated with mean PM2.5 , in the unadjusted and covariance-adjusted models. Similar trends were observed with maximum PM2.5 . CONCLUSION: There was a moderate improvement in lung stiffness of children exposed to PM2.5 from a local coalmine fire in infancy, consistent with an early deficit in lung function at 3-years after the fire that had resolved by 7-years.

Association between PM2.5 from a coal mine fire and FeNO concentration 7.5 years later.

BACKGROUND AND AIM: There are few long-term studies of respiratory health effects of landscape fires, despite increasing frequency and intensity due to climate change. We investigated the association between exposure to coal mine fire PM2.5 and fractional exhaled nitric oxide (FeNO) concentration 7.5 years later. METHODS: Adult residents of Morwell, who were exposed to the 2014 Hazelwood mine fire over 6 weeks, and unexposed residents of Sale, participated in the Hazelwood Health Study Respiratory Stream in 2021, including measurements of FeNO concentration, a marker of eosinophilic airway inflammation. Individual exposure to coal mine fire PM2.5 was modelled and mapped to time-location diaries. The effect of exposure to PM2.5 on log-transformed FeNO in exhaled breath was investigated using multivariate linear regression models in the entire sample and stratified by potentially vulnerable subgroups. RESULTS: A total of 326 adults (mean age: 57 years) had FeNO measured. The median FeNO level (interquartile range [IQR]) was 17.5 [15.0] ppb, and individual daily exposure to coal mine fire PM2.5 was 7.2 [13.8] µg/m3. We did not identify evidence of association between coal mine fire PM2.5 exposure and FeNO in the general adult sample, nor in various potentially vulnerable subgroups. The point estimates were consistently close to zero in the total sample and subgroups. CONCLUSION: Despite previous short-term impacts on FeNO and respiratory health outcomes in the medium term, we found no evidence that PM2.5 from the Hazelwood coal mine fire was associated with any long-term impact on eosinophilic airway inflammation measured by FeNO levels.

Vocational functioning in young people accessing services for first-episode psychosis and ultra-high risk of psychosis: A longitudinal naturalistic cohort study.

AIMS: Young people with first-episode psychosis (FEP) or at ultra-high risk (UHR) of psychosis often have lower vocational engagement than their peers. This study examines the effect of treatment in early intervention for psychosis services in Australia on engagement in education and employment. METHODS: This is a naturalistic sample of young people aged 12-25 with FEP (n = 1574) and UHR (n = 1515), accessing treatment in the headspace Early Psychosis (hEP) programme. Engagement in education and employment was assessed at baseline and every 90 days in treatment. Mixed effects logistic regression were used to analyse changes over time. RESULTS: On entering the hEP programme, approximately 49% of the young people with FEP and 28% of the young people at UHR status identified as Not in Education, Employment or Training (NEET). The odds of being NEET were reduced by 27% (95% confidence interval = [14, 39]) for every 6 months treatment for the FEP group, but no change in NEET status was observed in the UHR group. In both groups, absence from daily activities was significantly reduced during time in treatment. CONCLUSION: While there are methodological challenges analysing real-world non-control group cohort data, the findings indicate positive effects of the hEP programme on vocational and daily activity engagement for young people with FEP and at UHR status. A large proportion of the young people still identified as NEET after receiving treatment services, suggesting further refinement to ensure targeted and consistent vocational support throughout care.

Prevalence and Correlates of Tobacco Use in Young People Presenting to Australian Primary Mental Health Services.

INTRODUCTION: In Australian youth primary mental health settings it is unclear as to the rates and correlates of tobacco use at service entry. AIMS AND METHODS: We aimed to delineate the prevalence and correlates of recent tobacco use (eg, cigarettes, chewing tobacco, cigars, etc) in the past 3 months in young people at their first presentation to primary mental health services as a function of age. Cross-sectional self-report measures were collected using a tablet device from young people presenting to one of five Australian primary mental health (headspace) services. Logistic regression assessed correlates of past 3-month tobacco use in adolescents (12-17 years) and young adults (18-25 years). RESULTS: Regular (at least monthly) tobacco use in the past 3 months was found in 23.4% (n = 247, N = 1055) of the sample. Increasing age (odds ratio [OR] =1.47 per year; 95% confidence interval [CI]: 1.15 to 1.89), male sex (OR = 1.98; 95% CI: 1.02 to 3.83), being in a relationship (OR = 1.96; 95% CI: 1.01 to 3.82), and poorer functioning (OR = 0.95 per unit Social and Occupational Functioning Assessment Scale increase; 95% CI: 0.91 to 0.99) predicted regular tobacco use in adolescents, but not in young adults. Living in a regional location (OR = 2.10; 95% CI: 1.40 to 3.13) and not studying (OR = 0.47; 95% CI: 0.31 to 0.73) predicted tobacco use in young adults. Having a diagnosed mental illness other than depression and/or anxiety predicted tobacco use in both groups (adolescents OR = 2.49; 95% CI: 1.26 to 4.94; young adults OR = 1.80; 95% CI: 1.13 to 2.89). CONCLUSIONS: Nearly a quarter of young people with mental illness are using tobacco, supporting the need for early intervention approaches. Adapting treatment targets by age could improve the impact of interventions in adolescents versus young adults. Poor functioning and lack of engagement in education were associated with tobacco use in both age groups, respectively; however, more research is needed to determine the direction of these relationships. IMPLICATIONS: Young people with mental illness have a high prevalence of recent tobacco use and this is evident when they first present to youth primary mental health services. Youth-oriented mental health settings may provide a unique window for tobacco use prevention and early intervention to reduce smoking in people with mental illness, a priority population. Age-specific targeted approaches might be needed in adolescents and young adults.

Long-term impact of the 2014 Hazelwood coal mine fire on emergency department presentations in Australia.

BACKGROUND: In 2014, wildfires ignited a coal mine in Australia, burning for 6 weeks, releasing large amounts of fine particulate matter ≤2.5 µm in diameter (PM2.5). We investigated the association between individual PM2.5 exposure and emergency department presentations (EDPs) within 5 years post-fire. METHODS: Survey and exposure data for 2725 residents from an exposed and unexposed town were linked with ED administrative data from 2009 to 2019. The association between individual PM2.5 and EDPs was assessed using recurrent survival analysis. RESULTS: A 10 µg/m3 increase in PM2.5 was associated with a 10% increase in respiratory EDPs (HR = 1.10; 95%CI:1.00-1.22) over 5 years post-fire. Increased risks of EDPs for ischaemic heart disease (HR = 1.39; 95%CI:1.12-1.73), atherothrombotic disease (HR = 1.27; 95%CI:1.08-1.50), and cardiovascular disease (HR = 1.10, 95%CI:0.99-1.22) were evident within 2.5 years. CONCLUSION: PM2.5 exposure from a 6-week mine fire increased the 5-year risk of respiratory conditions. An increased risk of CVD within 2.5 years post-fire subsided after this time.

Somatic symptoms, psychological distress and trauma after disasters: lessons from the 2014 Hazelwood mine fire and 2019-20 Black Summer bushfires.

BACKGROUND: Wildfires cause significant physical and mental ill-health. How physical and mental symptoms interact following wildfire smoke exposure is unclear, particularly in the context of repeated exposures. In this cross-sectional study we investigated how posttraumatic stress and general psychological distress associated with somatic symptoms in a community exposed to multiple smoke events. METHODS: A random weighted sample of 709 adults exposed to smoke during the 2014 Hazelwood coal mine fire in south-eastern Australia completed a survey in 2020. The survey coincided with the Black Summer wildfires that caused a similar period of smoke haze in the region. Participants self-reported somatic symptoms (PHQ-15) and mine fire-related posttraumatic stress (IES-R) experienced over the previous week, general psychological distress (K10) experienced over the previous four weeks, lifetime health diagnoses and demographic information. Associations between posttraumatic stress, general psychological distress, and each PHQ-15 somatic symptom were analysed using ordinal logistic regression models. RESULTS: Overall, 36.2% of participants reported moderate- or high-level somatic symptomology. The most frequent somatic symptoms were fatigue, limb pain, trouble sleeping, back pain, headaches, and shortness of breath. After controlling for confounding factors, general psychological distress and posttraumatic stress were independently associated with all somatic symptoms (except menstrual problems in females for posttraumatic stress). CONCLUSIONS: Results highlight the high prevalence of somatic symptoms and their association with general psychological distress and posttraumatic stress within a community in the midst of a second large-scale smoke event. It is essential that healthcare providers and public health authorities consider the interconnections of these conditions when supporting communities affected by climate-related disasters.

No association between in utero exposure to emissions from a coalmine fire and post-natal lung function.

BACKGROUND AND OBJECTIVE: Studies linking early life exposure to air pollution and subsequent impaired lung health have focused on chronic, low-level exposures in urban settings. We aimed to determine whether in utero exposure to an acute, high-intensity air pollution episode impaired lung function 7-years later. METHOD: We conducted a prospective cohort study of children who lived in the vicinity of a coalmine fire. Respiratory function was measured using the forced oscillation technique (FOT). Z-scores for resistance at 5 Hz (R5), reactance at 5 Hz (X5) and area under the reactance curve (AX) were calculated. Two sets of analyses were conducted to address two separate questions: (1) whether mine fire exposure (a binary indicator; conceived after the mine fire vs in utero exposed) was associated with the respiratory Z-scores; (2) whether there was any dose-response relationship between fire-related PM2.5 exposure and respiratory outcomes among those exposed. RESULTS: Acceptable lung function measurements were obtained from 79 children; 25 unexposed and 54 exposed in utero. Median (interquartile range) for daily average and peak PM2.5 for the exposed children were 4.2 (2.6 - 14.2) and 88 (52-225) µg/m3 respectively. There were no detectable differences in Z-scores between unexposed and exposed children. There were no associations between respiratory Z-scores and in utero exposure to PM2.5 (daily average or peak). CONCLUSION: There was no detectable effect of in utero exposure to PM2.5 from a local coalmine fire on post-natal lung function 7-years later. However, statistical power was limited.

Exposure to air pollution concentrations of various intensities in early life and allergic sensitisation later in childhood.

BACKGROUND: Evidence on the relationship between air pollution and allergic sensitisation in childhood is inconsistent, and this relationship has not been investigated in the context of smoke events that are predicted to increase with climate change. Thus, we aimed to evaluate associations between exposure in two early life periods to severe levels of particulate matter with an aerodynamic diameter < 2.5 µm (PM2.5) from a mine fire, background PM2.5, and allergic sensitisation later in childhood. METHODS: We measured specific immunoglobulin E (IgE) levels for seven common aeroallergens as well as total IgE levels in a cohort of children who had been exposed to the Hazelwood coal mine fire, either in utero or during their first two years of life, in a regional area of Australia where ambient levels of PM2.5 are generally low. We estimated personal exposure to fire-specific emissions of PM2.5 based on a high-resolution meteorological and pollutant dispersion model and detailed reported movements of pregnant mothers and young children during the fire. We also estimated the usual background exposure to PM2.5 at the residential address at birth using a national satellite-based land-use regression model. Associations between both sources of PM2.5 and sensitisation to dust, cat, fungi, and grass seven years after the fire were estimated with logistic regression, while associations with total IgE levels were estimated with linear regression. RESULTS: No association was found between the levels of exposure at either developmental stage to fire-related PM2.5 and allergic sensitisation seven years after the event. However, levels of background exposure were positively associated with sensitisation to dust (OR = 1.90, 95%CI = 1.12,3.21 per 1 µg/m3). CONCLUSIONS: Chronic but low exposure to PM2.5 in early life could be more strongly associated with allergic sensitisation in childhood than time-limited high exposure levels, such as the ones experienced during landscape fires.

Predictors of suicidal ideation severity among treatment-seeking young people with major depressive disorder: The role of state and trait anxiety.

OBJECTIVE: Depression and suicidal ideation are closely intertwined. Yet, among young people with depression, the specific factors that contribute to changes in suicidal ideation over time are uncertain. Factors other than depressive symptom severity, such as comorbid psychopathology and personality traits, might be important contributors. Our aim was to identify contributors to fluctuations in suicidal ideation severity over a 12-week period in young people with major depressive disorder receiving cognitive behavioural therapy. METHODS: Data were drawn from two 12-week randomised, placebo-controlled treatment trials. Participants (N = 283) were 15-25 years old, with moderate to severe major depressive disorder. The primary outcome measure was the Suicidal Ideation Questionnaire, administered at baseline and weeks 4, 8 and 12. A series of linear mixed models was conducted to examine the relationship between Suicidal Ideation Questionnaire score and demographic characteristics, comorbid psychopathology, personality traits and alcohol use. RESULTS: Depression and anxiety symptom severity, and trait anxiety, independently predicted higher suicidal ideation, after adjusting for the effects of time, demographics, affective instability, non-suicidal self-injury and alcohol use. CONCLUSIONS: Both state and trait anxiety are important longitudinal correlates of suicidal ideation in depressed young people receiving cognitive behavioural therapy, independent of depression severity. Reducing acute psychological distress, through reducing depression and anxiety symptom severity, is important, but interventions aimed at treating trait anxiety could also potentially be an effective intervention approach for suicidal ideation in young people with depression.

Mental health systems modelling for evidence-informed service reform in Australia.

Australia's Fifth National Mental Health Plan required governments to report, not only on the progress of changes to mental health service delivery, but to also plan for services that should be provided. Future population demand for treatment and care is challenging to predict and one solution involves modelling the uncertain demands on the system. Modelling can help decision-makers understand likely future changes in mental health service demand and more intelligently choose appropriate responses. It can also support greater scrutiny, accountability and transparency of these processes. Australia has an emerging national capacity for systems modelling in mental health which can enhance the next phase of mental health reform. This paper introduces concepts useful for understanding mental health modelling and identifies where modelling approaches can support health service planners to make evidence-informed decisions regarding planning and investment for the Australian population.

Sociodemographic circumstances, health, and life experience shape posttraumatic distress trajectories among individuals exposed to smoke during a large-scale coal mine fire.

The 2014 Hazelwood coal mine fire in the Latrobe Valley, Australia, distributed toxic smoke into surrounding communities over 45 days. This study investigated risk and protective factors associated with four trajectories of posttraumatic distress (resilient, recovery, delayed-onset, chronic) among exposed adults. Participants (N = 709) completed surveys in 2016-2017 and 2019-2020 assessing mine fire-related particulate matter (PM2.5 ) exposure; sociodemographic, physical, and mental health variables; and exposure to other traumatic and recent stressful events. Mine fire-related posttraumatic distress was measured using the IES-R; trajectories were determined according to established clinical significance thresholds. Relative risk ratios (RRRs) were generated from multivariate multinomial regressions. The resilient trajectory was most common (77.0%). The chronic trajectory (8.5%) was associated with loneliness, RRR = 2.59, 95% CI [1.30, 5.16], and physical health diagnoses, RRR = 2.31, 95% CI [1.32, 4.02]. The delayed-onset trajectory (9.1%) was associated with multiple recent stressful events, RRR = 2.51, 95% CI [1.37, 4.59]; mental health diagnoses, RRR = 2.30, 95% CI [1.25, 4.24]; loneliness, RRR = 2.05, 95% CI [1.09, 3.88]; and male gender, RRR = 2.01, 95% CI [1.18, 3.44]. Socioeconomic advantage protected against chronic, RRR = 0.68, 95% CI [0.53, 0.86], and delayed-onset trajectory membership, RRR = 0.68, 95% CI [0.50, 0.94]; social support protected against chronic trajectory membership, RRR = 0.67, 95% CI [0.49, 0.92]. PM2.5 exposure did not determine trajectory. These findings enhance understanding of longer-term posttraumatic responses to large-scale smoke events and can inform mental health initiatives within at-risk communities.

Understanding the complexity, patterns, and correlates of alcohol and other substance use among young people seeking help for mental ill-health.

PURPOSE: Use of alcohol and other substances is a multifaceted issue impacting young people across multiple life domains. This paper aims to elucidate patterns of substance use and associated demographic and clinical factors among young people seeking treatment for their mental health. METHODS: Young people (12-25 years old) were recruited from five youth-specific primary mental health ("headspace") services in Australia. Self-reported substance use and harms in the past 3 months were measured using WHO-ASSIST. Network analyses were conducted to evaluate interrelationships between use and harms associated with different substances. Subgroups were then identified based on whether participants reported using high centrality substances, and associated demographic and clinical factors were assessed with multinomial logistic regression. RESULTS: 1107 youth participated. 70% reported use of at least one substance in the past 3 months, with around 30% of those reporting related health, social, legal or financial problems. Network analysis highlighted substantial interconnections between use and harm indicators for all substances, with amphetamine-type stimulants (ATS) and cannabis being high central substances. Higher levels of substance use and harms were reported in subgroups with ATS or cannabis use and different risk factors were associated with these subgroups. CONCLUSIONS: Findings highlight the importance of screening for substance use in youth primary mental healthcare settings, offering a key opportunity for early intervention. Clinicians should be aware of the inner connections of use and harms of different drugs and the role of cannabis and amphetamine use as a marker for more substance use profiles.

Accelerating youth mental health services research.

OBJECTIVE: We describe a research program to advance youth mental health service research in Australia, addressing two core knowledge gaps: the lack of available routine outcome measures and lack of understanding of how to assess and monitor complexity and heterogeneity in illness presentation and trajectory. CONCLUSIONS: Our research identifies better routine outcome measures (ROM) that are: designed specifically for the developmental nuances of the 12-25-year age range; multidimensional; and meaningful to young people, their carers, and service providers. Alongside much-needed new measures of complexity and heterogeneity, these tools will inform service providers to better meet the needs of young people presenting with mental health problems.

The impact of the Hazelwood coal mine fire smoke exposure on asthma.

OBJECTIVE: In 2014, a fire at an open cut coal mine in South-eastern Australia burned for about 6 weeks. Residents of the adjacent town were exposed to high levels of fine particulate matter (PM2.5) during this period. Three and a half years after the event, this study aimed to investigate potential long-term impacts of short-term exposure to coal mine fire smoke on asthma. METHODS: A cross-sectional analysis was undertaken in a group of exposed participants with asthma from Morwell (n = 165) and a group of unexposed participants with asthma from the control town of Sale (n = 64). Exposure was determined by modeled PM2.5 data for the mine fire period. Respiratory symptoms were assessed with a validated respiratory health questionnaire and symptom severity score. Asthma control was assessed with a validated questionnaire. Lung function testing included spirometry, bronchodilator response, and fraction of exhaled nitric oxide. RESULTS: There was no evidence that exposed participants had more severe asthma symptoms, worse lung function, or more eosinophilic airway inflammation than unexposed participants. However, there was some evidence that Morwell participants had more uncontrolled than well-controlled asthma, compared to the participants from Sale (adjusted relative risk ratio 2.71 95% CI: 1.02, 7.21, p = .046). CONCLUSION: Three and a half years after exposure, coal mine fire smoke did not appear to be associated with more severe asthma symptoms or worse lung function but might be associated with poorer asthma control.