Study protocol for the Australian autism biobank: an international resource to advance autism discovery research

The relationship between hair cortisol concentration and autism diagnosis

BACKGROUND

Autistic children are prone to experience heightened levels of distress and physiological reactivity to a range of sensory, social, and emotional stimuli. In line with this, multiple studies have demonstrated that autistic children have higher acute cortisol stress responses to adverse or threatening stimuli and altered cortisol awakening responses. However, few studies have examined whether this sensitivity may relate to heightened levels of chronic stress and persistently elevated hypothalamic-pituitary-adrenal (HPA) axis activity. The measurement of cortisol accumulation in hair is considered a non-invasive biomarker of chronic stress and has been associated with several childhood diseases. Here, we investigated whether hair cortisol concentration in a large sample of autistic children differed from non-autistic children, and after accounting for a range of child, parental and family-level characteristics.

METHODS

Hair cortisol concentration was measured in 307 autistic children and 282 non-autistic controls aged between 2 and 17 years recruited from four Australian states who participated in providing hair samples and demographic data to the Australian Autism Biobank. Independent samples t-test or one-way analysis of variance (ANOVA) were conducted to determine significant differences in the mean hair cortisol concentration (pg/mg) between potential covariates. Primary analysis included multivariable regression modelling of the collapsed sample to identify variables that were significantly associated with hair cortisol concentration after controlling for covariates. We also accounted for the potential interaction of multiple biological (e.g., age, sex, BMI) and psychosocial characteristics at the level of the child, the mother and the father, and the family unit.

RESULTS

Our findings suggest that the diagnosis of autism was not a significant predictor of chronic stress, as measured by hair cortisol concentration. However, findings of the multivariable regression analysis showed that key factors such as area of residence (Queensland vs Victorian state of residence) and decrease in child's age were significantly associated with higher hair cortisol concentration whereas lower family income was significantly associated with higher hair cortisol concentration.

CONCLUSION

To our knowledge, this is the first study to show that socioeconomic factors such as family annual income affect hair cortisol status in autistic children, indicating that the psychosocial environment may be a potential mediator for chronic stress in autistic children just as it has been demonstrated in non-autistic children.

Absence of association between maternal adverse events and long-term gut microbiome outcomes in the Australian autism biobank

Introduction

Maternal immune activation (MIA) and prenatal maternal stress (MatS) are well-studied risk factors for psychiatric conditions such as autism and schizophrenia. Animal studies have proposed the gut microbiome as a mechanism underlying this association and have found that risk factor-related gut microbiome alterations persist in the adult offspring. In this cross-sectional study, we assessed whether maternal immune activation and prenatal maternal stress were associated with long-term gut microbiome alterations in children using shotgun metagenomics.

Methods

This cross-sectional study included children diagnosed with autism (N = 92), siblings without a diagnosis (N = 42), and unrelated children (N = 40) without a diagnosis who were recruited into the Australian Autism Biobank and provided a faecal sample. MIA exposure was inferred from self-reported data and included asthma/allergies, complications during pregnancy triggering an immune response, auto-immune conditions, and acute inflammation. Maternal stress included any of up to 9 stressful life events during pregnancy, such as divorce, job loss, and money problems. Data were analysed for a total of 174 children, of whom 63 (36%) were born to mothers with MIA and 84 (48%) were born to mothers who experienced maternal stress during pregnancy (where 33 [19%] experienced both). Gut microbiome data was assessed using shotgun metagenomic sequencing of the children's faecal samples.

Results

In our cohort, MIA, but not MatS, was associated with ASD. Variance component analysis revealed no associations between any of the gut microbiome datasets and neither MIA nor MatS. After adjusting for age, sex, diet and autism diagnosis, there was no significant difference between groups for bacterial richness, α-diversity or β-diversity. We found no significant differences in species abundance in the main analyses. However, when stratifying the cohort by age, we found that Faecalibacterium prausnitzii E was significantly decreased in MIA children aged 11-17.

Discussion

Consistent with previous findings, we found that children who were born to mothers with MIA were more likely to be diagnosed with autism. Unlike within animal studies, we found negligible microbiome differences associated with MIA and maternal stress. Given the current interest in the microbiome-gut-brain axis, researchers should exercise caution in translating microbiome findings from animal models to human contexts and the clinical setting.

Sex Differences in the Broad Autism Phenotype: Insights from the Australian Biobank

Examining sub-threshold autistic traits in non-autistic first-degree relatives of individuals on the autism spectrum, known as the Broad Autism Phenotype (BAP), could provide new insights into the associations and familial aggregation of autistic traits. This study was a retrospective cross-sectional study of parents (n = 1008), probands with autism (n = 613), and unaffected siblings (n = 221) of probands with autism. BAP traits were examined by the BAP Questionnaire and Communication Checklist-Adult in parents, Autism Developmental Observation Scale-Second edition in probands, and Social Responsiveness Scale in siblings. Multivariable linear regression analyses were used to investigate the associations of parental BAP traits on autistic traits in probands and unaffected sibling BAP traits. Fathers showed significantly increased aloofness, pragmatic language difficulties, and social engagement problems compared to mothers. Female siblings showed increased difficulties with social cognition compared to male siblings. Adjusted models of the regression analyses showed that all BAP traits in fathers were significantly associated with BAP trait expression in probands with autism. Additionally, all of mother's BAP traits were significantly associated with unaffected siblings' BAP trait expression while only fathers' aloofness and rigidity traits were inversely associated with siblings' BAP trait expression. Finally, there were significant inverse interactions noted between parent's BAP traits and their children's BAP trait expression. This study demonstrated differences in how males and females express BAP traits and also identified differences in parent-child associations by sex, with fathers having a greater effect on their proband children's expression of BAP traits than mothers.

Contributing to an autism biobank: Diverse perspectives from autistic participants, family members and researchers

LAY ABSTRACT

A lot of autism research has focused on finding genes that might cause autism. To conduct these genetic studies, researchers have created 'biobanks' - collections of biological samples (such as blood, saliva, urine, stool and hair) and other health information (such as cognitive assessments and medical histories). Our study focused on the Australian Autism Biobank, which collected biological and health information from almost 1000 Australian autistic children and their families. We wanted to know what people thought about giving their information to the Biobank and why they chose to do so. We spoke to 71 people who gave to the Biobank, including 18 autistic adolescents and young adults, 46 of their parents and seven of their siblings. We also spoke to six researchers who worked on the Biobank project. We found that people were interested in giving their information to the Biobank so they could understand why some people were autistic. Some people felt knowing why could help them make choices about having children in the future. People also wanted to be involved in the Biobank because they believed it could be a resource that could help others in the future. They also trusted that scientists would keep their information safe and were keen to know how that information might be used in the future. Our findings show that people have lots of different views about autism biobanks. We suggest researchers should listen to these different views as they develop their work.

Utilising Behavioural and Sensory Profiles and Associated Perinatal Factors to Identify Meaningful Subgroups in Autism Spectrum Disorder

The heterogeneity of autism spectrum disorder (ASD) clinically and aetiologically hinders intervention matching and prediction of outcomes. This study investigated if the behavioural, sensory, and perinatal factor profiles of autistic children could be used to identify distinct subgroups. Participants on the autism spectrum aged 2 to 17 years and their families were sourced via the Australian Autism Biobank (AAB). Latent class analysis was used to identify subgroups within this cohort, utilising twenty-six latent variables representing child's behavioural and sensory features and perinatal factors. Four distinct subgroups within the sample (n = 1168) distinguished by sensory and behavioural autism traits and exposure to perinatal determinants were identified. Class 2 and Class 4, which displayed the greatest behavioural and sensory impairment respectively, were associated with the highest perinatal factor exposure. Class 1, labelled "Most behavioural concerns and moderate sensory and behavioural skills concerns" had mixed exposure to perinatal determinants while Class 3, named "Least sensory and behavioural skills concerns" had the least perinatal determinant exposure, indicating a directly proportional correlation between severity of clinical features and perinatal factor exposure. Additionally, association between specific exposures such as maternal mental illness in Class 1 and significant behavioural concerns was recognised. Identifying distinct subgroups among autistic children can lead to development of targeted interventions and supports. Close monitoring of children exposed to specific perinatal determinants for developmental differences could assist early intervention and supports.

Investigating Parental Observations of Early Autism Development in Simplex and Multiplex Families

Past research has highlighted the importance of early identification of developmental differences to improve targeted access to early interventions or supports. As such, it is of particular importance in the context of children at elevated likelihood of autism (such as where an older sibling has a diagnosis of autism), to better understand when and which early concerns are important as predictors of which children will benefit from pre-diagnostic supports. This study explored the number and frequency of retrospective parent reported concerns within the first year of life for children diagnosed with autism, both those who had an older sibling diagnosed with autism and those who did not, as well as for undiagnosed siblings. We found that at both 0-6 and 7-12 months, the only factor related to the presence or absence of early parent reported concerns was child diagnostic status, with the presence of reported early concerns more likely for children with a diagnosis of autism. These findings suggest that for children at elevated likelihood of autism, parents' concerns are driven primarily by developmental differences, with child's birth order and sibling diagnostic status not impacting on parent early concerns.

Identification of subgroups of children in the Australian Autism Biobank using latent class analysis

BACKGROUND

The identification of reproducible subtypes within autistic populations is a priority research area in the context of neurodevelopment, to pave the way for identification of biomarkers and targeted treatment recommendations. Few previous studies have considered medical comorbidity alongside behavioural, cognitive, and psychiatric data in subgrouping analyses. This study sought to determine whether differing behavioural, cognitive, medical, and psychiatric profiles could be used to distinguish subgroups of children on the autism spectrum in the Australian Autism Biobank (AAB).

METHODS

Latent profile analysis was used to identify subgroups of children on the autism spectrum within the AAB (n = 1151), utilising data on social communication profiles and restricted, repetitive, and stereotyped behaviours (RRBs), in addition to their cognitive, medical, and psychiatric profiles.

RESULTS

Our study identified four subgroups of children on the autism spectrum with differing profiles of autism traits and associated comorbidities. Two subgroups had more severe clinical and cognitive phenotype, suggesting higher support needs. For the 'Higher Support Needs with Prominent Language and Cognitive Challenges' subgroup, social communication, language and cognitive challenges were prominent, with prominent sensory seeking behaviours. The 'Higher Support Needs with Prominent Medical and Psychiatric and Comorbidity' subgroup had the highest mean scores of challenges relating to social communication and RRBs, with the highest probability of medical and psychiatric comorbidity, and cognitive scores similar to the overall group mean. Individuals within the 'Moderate Support Needs with Emotional Challenges' subgroup, had moderate mean scores of core traits of autism, and the highest probability of depression and/or suicidality. A fourth subgroup contained individuals with fewer challenges across domains (the 'Fewer Support Needs Group').

LIMITATIONS

Data utilised to identify subgroups within this study was cross-sectional as longitudinal data was not available.

CONCLUSIONS

Our findings support the holistic appraisal of support needs for children on the autism spectrum, with assessment of the impact of co-occurring medical and psychiatric conditions in addition to core autism traits, adaptive functioning, and cognitive functioning. Replication of our analysis in other cohorts of children on the autism spectrum is warranted, to assess whether the subgroup structure we identified is applicable in a broader context beyond our specific dataset.

Dental care experiences and clinical phenotypes in children on the autism spectrum

AIMS

Children diagnosed with autism spectrum disorder may be at higher likelihood of experiencing poorer oral health and difficulties accessing dental health care. However, identifying which children on the autism spectrum may be more vulnerable to experiencing dental care difficulties is still unknown. This study investigated parental reports of oral health and dental service needs of children diagnosed with autism and explored relationships with clinical phenotypes.

METHODS AND RESULTS

Participants (n = 140) were parents of children on the autism spectrum who had participated in a large national biobank study, the Australian Autism Biobank, invited to complete additional surveys about oral health, service use, and barriers to care. One third of parents reported their child's oral health was worse than other children the same age, with 26% reporting untreated dental problems. A third of children were reported to have undergone general anaesthesia at least once for dental procedures. Children who had undergone general anaesthesia were more likely to have intellectual disability and greater functional difficulties. Parents of children with greater functional limitations and sensory challenges reported experiencing barriers to accessing dental care more frequently.

CONCLUSION

These results have important implications for paediatric dentists working with children diagnosed with autism with co-occurring intellectual, functional, and sensory challenges. Findings may inform the development of more personalised autism-specific supports.

Dietary intake in children on the autism spectrum is altered and linked to differences in autistic traits and sensory processing styles

Diets of children and adolescents on the autism spectrum often differ when compared to their non-autistic peers. Most dietary studies have been limited by small sample sizes and rarely assess the heterogeneity of autism. Addressing this gap, this study compared the anthropometrics, dietary composition, dietary quality, and food variety of 154 Australian children and adolescents on the spectrum and 213 non-autistic children (71 siblings and 142 unrelated controls). Beyond the case-control approach, within-group comparisons assessed the influence of autism clinical presentations and sensory processing styles on body mass index (BMI) and measures of dietary intake among those on the spectrum. In this word first study of diet that included between-group comparisons with non-autistic peers (siblings and an unrelated comparison group) and within-autism group comparisons, we found that children on the spectrum consumed limited variety and lower quality of food and non-autistic siblings also ate comparably higher levels of energy-dense, nutrient poor food, and less diary. This may be due to autistic traits influencing family's diets or shared sensory sensitivities driving dietary intake. Within the autism group, higher autistic traits were associated with lower BMIs and a specific dietary pattern higher in simple carbohydrates and lower in unprocessed protein. Contrastingly, greater sensitivity to sensory stimuli was associated with a healthier diet. Increased age was linked to more varied diets but also diets higher in saturated fats and energy-dense, nutrient poor foods. Overall, this research highlights that potential mediators of dietary intake, such as familial influences, autistic traits, sensory processing styles, age and sex, need to be considered when assessing diet in the autistic population. LAY SUMMARY: In this study of dietary differences linked to autism, children, and teenagers on the spectrum ate fewer different foods and were less likely to eat recommended amounts of fruits and vegetables when compared to non-autistic siblings and unrelated children and teenagers. There were also family differences, in that those on the spectrum and their siblings ate more unhealthy foods and less dairy. Among those on the spectrum, dietary differences were linked to age, sex, autistic traits and sensory processing styles.

Patterns of sensory modulation by age and sex in young people on the autism spectrum

Sensory modulation symptoms form a diagnostic criterion for autism spectrum disorder and are associated with significant daily functional limitations. Utilizing caregiver report on Short Sensory Profile-2 (SSP-2) for 919 autistic children (3-14.11 years), we examined the expression of sensory modulation symptoms by age and sex and investigated the existence of specific sensory modulation subtypes. Sensory modulation symptoms appeared to peak in frequency during middle childhood, particularly in sensory sensitivity and avoidance. Symptoms associated with sensory hypo-reactivity and seeking tended not differ between age cohorts. Males and females demonstrated similar overall sensory modulation profiles, however, females showed elevated symptoms relating to sensory sensitivity. Model-based cluster analysis revealed five interpretable sensory modulation subtypes which related to symptom severity (low, mid-range, high). Subtypes demonstrating mid-range symptom severity differed in focus on sensory hyper-reactivity or seeking symptoms. The findings of this study report for the first time that age-related differences in sensory modulation symptoms may be associated with sensory hyper-reactivity only. The subtyping results also suggest that sensory modulation symptom severity is a reliable means of classifying variance within autistic children, however, consideration of differences in the behavioral strategies employed by individuals to manage sensory modulation symptoms may inform tailored supportive strategies.

Clinical and behavioral attributes leading to sleep disorders in children on the autism spectrum

Sleep disorders are a common comorbid condition in children diagnosed with autism spectrum disorder ("autism"). However, the relationship between the clinical features of autism and sleep disorders remains unclear. A better understanding of the inherent autism-related characteristics linked to comorbid sleep disorders would improve comprehensive assessment and management. This study examined the relationship between sociodemographics, autism symptoms, sleep problems, cognitive status, behavioral attributes, and sensory profiles. Using data from 1268 participants who took part in the Australian Autism Biobank, sleep-related measurements using the Child Sleep Habits Questionnaire (CSHQ) were compared between autistic children aged 2 to 17 (N = 969), their siblings (N = 188), and unrelated children without an autism diagnosis (N = 111). The known relationship between sleep problems and autism was further explored by including scores from the Autism Diagnostic Observation Schedule-2, Mullen Scales of Early Learning, Vineland Adaptive Behavioral Scale-II and the Short Sensory Profile-2; which were included in analyses for autistic participants who had a completed CSHQ. Multiple regression models were used to identify clinical/behavioral variables associated with CSHQ subscales. The autism group had a significantly higher total CSHQ score than the sibling and comparison groups (p < 0.001), indicating worse sleep quality. Within the autism group, lower adaptive behaviors (i.e., VABS-II) and sensory issues (i.e., SSP-2 subclass scores) were positively associated with the severity of sleep problems (i.e., the CSHQ subclass scores) (p < 0.001). The significant functional impact of poor sleep on autistic children warrants an assessment of sleep as a critical part of a holistic approach to supporting autistic children and their families. LAY SUMMARY: Autistic children generally have co-occurring conditions. Sleep disorders impact approximately 50%-80% of autistic children. The impact on the quality of life for both the children and their families can be significant. This study compares sleep problems in autistic children and adolescents with their siblings and children without a diagnosis of autism, and investigates the relationship between specific autistic traits, daily life behaviors and sleep problems. The findings highlight the importance of a holistic assessment for autistic children and matching appropriate sleep intervention and supports where indicated.

Parent-reported Early Atypical Development and Age of Diagnosis for Children with Co-occurring Autism and ADHD

Autism and attention-deficit/hyperactivity disorder (ADHD) often co-occur. This survey of 288 New Zealand parents of children diagnosed with autism (n = 111), ADHD (n = 93), or both conditions (n = 84), examined the relations between age of diagnosis and early atypical development, the age specialist consultation was needed and types of specialists seen. Co-occurring autism and ADHD was associated with an earlier ADHD diagnosis and a later autism diagnosis. Parents of children with both diagnoses reported less atypical development in language and social behaviours compared to parents of children of autism, and this co-occurring group also experienced longer wait times to diagnosis, and saw more types of specialists prior to a diagnosis, than those with autism.

Genetic Pathways Associated With Sleep Problems in Children With Autism Spectrum Disorder

AIMS

Children on the autism spectrum are more likely to have sleep problems than non-autistic children. Sleep disturbance may exacerbate emotional and behavioral problems of children on the autism spectrum. A better understanding of the biological mechanisms underlying sleep disturbance provide clues to better management for this co-morbid condition in autism. The goal of the current study is to identify genetic variants associated with sleep disturbance and melatonin levels in autistic children.

METHODS

A total of 969 children on the autism spectrum were genotyped using the Global Screening Array v1 or Global Screening Array v2. Sleep problems were assessed using the Children's Sleep Habits Questionnaire (CSHQ). Melatonin levels were measured using the urine samples of 219 probands. The relationship between the melatonin level and CSHQ score was examined using the general linear model. The genetic variants associated with the CSHQ score and melatonin level as two separate quantitative traits were determined using genomewide association studies.

RESULTS

The data indicates that urine melatonin levels were positively associated with CSHQ scores, suggesting that autistic children with a poorer sleep qualiy could has higher melatonin level. Furthermore, genetic assocication studies suggest that genetic pathways involved in pro-inflammatory responses might be involved in sleep disturbance, while genetic pathways involved in catecholamine-secreting PC12 cells and Schwann cells could be associated with melatonin levels.

CONCLUSIONS

Taken together, our findings indicate that sleep disturbance and melatonin metabolism could be attributable to distinct biological mechanisms in autistic children since they might not share genetic contributors.

Co-Design of a Neurodevelopment Assessment Scale: A Study Protocol

Neurodevelopmental disorders are a heterogeneous group of conditions with overlapping symptomatology and fluctuating developmental trajectories that transcend current diagnostic categorisation. There is a need for validated screening instruments which dimensionally assess symptomatology from a holistic, transdiagnostic perspective. The primary aim is to co-design a Neurodevelopment Assessment Scale (NAS), a user-friendly transdiagnostic assessment inventory that systematically screens for all signs and symptoms commonly encountered in neurodevelopmental disorders. Our first objective is to undertake development of this tool, utilising co-design principles in partnership with stakeholders, including both those with lived experience of neurodevelopmental disorders and service providers. Our second objective is to evaluate the face validity, as well as the perceived utility, user-friendliness, suitability, and acceptability (i.e., 'social validity'), of the NAS from the perspective of parents/caregivers and adults with neurodevelopmental disorders, clinicians, and service providers. Our third objective is to ascertain the psychometric properties of the NAS, including content validity and convergent validity. The NAS will provide an efficient transdiagnostic tool for evaluating all relevant signs, symptoms, and the dimensional constructs that underpin neurodevelopmental presentations. It is anticipated that this will maximise outcomes by enabling the delivery of personalised care tailored to an individual's unique profile in a holistic and efficient manner.

Autism-related dietary preferences mediate autism-gut microbiome associations

There is increasing interest in the potential contribution of the gut microbiome to autism spectrum disorder (ASD). However, previous studies have been underpowered and have not been designed to address potential confounding factors in a comprehensive way. We performed a large autism stool metagenomics study (n = 247) based on participants from the Australian Autism Biobank and the Queensland Twin Adolescent Brain project. We found negligible direct associations between ASD diagnosis and the gut microbiome. Instead, our data support a model whereby ASD-related restricted interests are associated with less-diverse diet, and in turn reduced microbial taxonomic diversity and looser stool consistency. In contrast to ASD diagnosis, our dataset was well powered to detect microbiome associations with traits such as age, dietary intake, and stool consistency. Overall, microbiome differences in ASD may reflect dietary preferences that relate to diagnostic features, and we caution against claims that the microbiome has a driving role in ASD.

Characterising the Early Presentation of Motor Difficulties in Autistic Children

This study aimed to explore the rates of motor difficulties in children from the Australian Autism Biobank, and how early motor concerns impacted on children functionally. Children with autism aged 2-7 years, including 441 with a Vineland Adaptive Behavior Scale (VABS-II) motor subscale and 385 with a Mullen Scales of Early Learning (MSEL) fine motor subscale were included (n total = 514; 80% male). Approximately 60% of children on the MSEL and ~ 25% on the VABS-II had clinically significant motor impairments. More children with delayed sitting and walking motor milestones had early childhood parent reported motor difficulties (p < 0.001). Early motor delays or concerns may assist identifying individuals who will likely benefit from early ongoing developmental monitoring and early support.

The Monash Autism-ADHD genetics and neurodevelopment (MAGNET) project design and methodologies: a dimensional approach to understanding neurobiological and genetic aetiology

Background

ASD and ADHD are prevalent neurodevelopmental disorders that frequently co-occur and have strong evidence for a degree of shared genetic aetiology. Behavioural and neurocognitive heterogeneity in ASD and ADHD has hampered attempts to map the underlying genetics and neurobiology, predict intervention response, and improve diagnostic accuracy. Moving away from categorical conceptualisations of psychopathology to a dimensional approach is anticipated to facilitate discovery of data-driven clusters and enhance our understanding of the neurobiological and genetic aetiology of these conditions. The Monash Autism-ADHD genetics and neurodevelopment (MAGNET) project is one of the first large-scale, family-based studies to take a truly transdiagnostic approach to ASD and ADHD. Using a comprehensive phenotyping protocol capturing dimensional traits central to ASD and ADHD, the MAGNET project aims to identify data-driven clusters across ADHD-ASD spectra using deep phenotyping of symptoms and behaviours; investigate the degree of familiality for different dimensional ASD-ADHD phenotypes and clusters; and map the neurocognitive, brain imaging, and genetic correlates of these data-driven symptom-based clusters.

Methods

The MAGNET project will recruit 1,200 families with children who are either typically developing, or who display elevated ASD, ADHD, or ASD-ADHD traits, in addition to affected and unaffected biological siblings of probands, and parents. All children will be comprehensively phenotyped for behavioural symptoms, comorbidities, neurocognitive and neuroimaging traits and genetics.

Conclusion

The MAGNET project will be the first large-scale family study to take a transdiagnostic approach to ASD-ADHD, utilising deep phenotyping across behavioural, neurocognitive, brain imaging and genetic measures.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13229-021-00457-3.

Investigating associations between birth order and autism diagnostic phenotypes

BACKGROUND

Birth order effects have been linked to variability in intelligence, educational attainment and sexual orientation. First- and later-born children have been linked to an increased likelihood of an Autism Spectrum Disorder (ASD) diagnosis, with a smaller body of evidence implicating decreases in cognitive functioning with increased birth order. The present study investigated the potential association between birth order and ASD diagnostic phenotypes in a large and representative population sample.

METHODS

Data were obtained from an ongoing prospective diagnostic registry, collected between 1999 and 2017, including children (1-18 years of age, n = 5,404) diagnosed with ASD in the state of Western Australia. Children with ASD were ranked relative to sibling's birth to establish birth order within families at time of ASD diagnosis. Information reported to the registry by health professionals at the time of diagnostic evaluation included demographic and family characteristics, functional abilities and intellectual capacity.

RESULTS

Adaptive functioning and intelligence scores decreased with increasing birth order, with later-born children more likely to have an intellectual disability. Compared to first-born children with siblings, first-born children without siblings at the time of diagnosis also exhibited decreased cognitive functioning.

CONCLUSIONS

These findings demonstrate for the first time an association between increasing birth order and variability in ASD clinical phenotypes at diagnosis, with potential evidence of reproductive curtailment in children without siblings. Taken together, these findings have significant implications for advancing understanding about the potential mechanisms that contribute to heterogeneity in ASD clinical presentations as a function of birth order and family size.

Repetitive transcranial magnetic stimulation (rTMS) in autism spectrum disorder: protocol for a multicentre randomised controlled clinical trial

INTRODUCTION

There are no well-established biomedical treatments for the core symptoms of autism spectrum disorder (ASD). A small number of studies suggest that repetitive transcranial magnetic stimulation (rTMS), a non-invasive brain stimulation technique, may improve clinical and cognitive outcomes in ASD. We describe here the protocol for a funded multicentre randomised controlled clinical trial to investigate whether a course of rTMS to the right temporoparietal junction (rTPJ), which has demonstrated abnormal brain activation in ASD, can improve social communication in adolescents and young adults with ASD.

METHODS AND ANALYSIS

This study will evaluate the safety and efficacy of a 4-week course of intermittent theta burst stimulation (iTBS, a variant of rTMS) in ASD. Participants meeting criteria for Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition ASD (n=150, aged 14-40 years) will receive 20 sessions of either active iTBS (600 pulses) or sham iTBS (in which a sham coil mimics the sensation of iTBS, but no active stimulation is delivered) to the rTPJ. Participants will undergo a range of clinical, cognitive, epi/genetic, and neurophysiological assessments before and at multiple time points up to 6 months after iTBS. Safety will be assessed via a structured questionnaire and adverse event reporting. The study will be conducted from November 2020 to October 2024.

ETHICS AND DISSEMINATION

The study was approved by the Human Research Ethics Committee of Monash Health (Melbourne, Australia) under Australia's National Mutual Acceptance scheme. The trial will be conducted according to Good Clinical Practice, and findings will be written up for scholarly publication.

TRIAL REGISTRATION NUMBER

Australian New Zealand Clinical Trials Registry (ACTRN12620000890932).

Analysis of common genetic variation and rare CNVs in the Australian Autism Biobank

BACKGROUND

Autism spectrum disorder (ASD) is a complex neurodevelopmental condition whose biological basis is yet to be elucidated. The Australian Autism Biobank (AAB) is an initiative of the Cooperative Research Centre for Living with Autism (Autism CRC) to establish an Australian resource of biospecimens, phenotypes and genomic data for research on autism.

METHODS

Genome-wide single-nucleotide polymorphism genotypes were available for 2,477 individuals (after quality control) from 546 families (436 complete), including 886 participants aged 2 to 17 years with diagnosed (n = 871) or suspected (n = 15) ASD, 218 siblings without ASD, 1,256 parents, and 117 unrelated children without an ASD diagnosis. The genetic data were used to confirm familial relationships and assign ancestry, which was majority European (n = 1,964 European individuals). We generated polygenic scores (PGS) for ASD, IQ, chronotype and height in the subset of Europeans, and in 3,490 unrelated ancestry-matched participants from the UK Biobank. We tested for group differences for each PGS, and performed prediction analyses for related phenotypes in the AAB. We called copy-number variants (CNVs) in all participants, and intersected these with high-confidence ASD- and intellectual disability (ID)-associated CNVs and genes from the public domain.

RESULTS

The ASD (p = 6.1e-13), sibling (p = 4.9e-3) and unrelated (p = 3.0e-3) groups had significantly higher ASD PGS than UK Biobank controls, whereas this was not the case for height-a control trait. The IQ PGS was a significant predictor of measured IQ in undiagnosed children (r = 0.24, p = 2.1e-3) and parents (r = 0.17, p = 8.0e-7; 4.0% of variance), but not the ASD group. Chronotype PGS predicted sleep disturbances within the ASD group (r = 0.13, p = 1.9e-3; 1.3% of variance). In the CNV analysis, we identified 13 individuals with CNVs overlapping ASD/ID-associated CNVs, and 12 with CNVs overlapping ASD/ID/developmental delay-associated genes identified on the basis of de novo variants.

LIMITATIONS

This dataset is modest in size, and the publicly-available genome-wide-association-study (GWAS) summary statistics used to calculate PGS for ASD and other traits are relatively underpowered.

CONCLUSIONS

We report on common genetic variation and rare CNVs within the AAB. Prediction analyses using currently available GWAS summary statistics are largely consistent with expected relationships based on published studies. As the size of publicly-available GWAS summary statistics grows, the phenotypic depth of the AAB dataset will provide many opportunities for analyses of autism profiles and co-occurring conditions, including when integrated with other omics datasets generated from AAB biospecimens (blood, urine, stool, hair).

Characterizing the Interplay Between Autism Spectrum Disorder and Comorbid Medical Conditions: An Integrative Review

Co-occurring medical disorders and associated physiological abnormalities in individuals with autism spectrum disorder (ASD) may provide insight into causal pathways or underlying biological mechanisms. Here, we review medical conditions that have been repeatedly highlighted as sharing the strongest associations with ASD-epilepsy, sleep, as well as gastrointestinal and immune functioning. We describe within each condition their prevalence, associations with behavior, and evidence for successful treatment. We additionally discuss research aiming to uncover potential aetiological mechanisms. We then consider the potential interaction between each group of conditions and ASD and, based on the available evidence, propose a model that integrates these medical comorbidities in relation to potential shared aetiological mechanisms. Future research should aim to systematically examine the interactions between these physiological systems, rather than considering these in isolation, using robust and sensitive biomarkers across an individual's development. A consideration of the overlap between medical conditions and ASD may aid in defining biological subtypes within ASD and in the development of specific targeted interventions.