Sibling Recurrence Risk and Cross-aggregation of Attention-Deficit/Hyperactivity Disorder and Autism Spectrum Disorder

The association between prenatal oxidative stress levels measured by isoprostanes and offspring neurodevelopmental outcomes at 36 months

Oxidative stress during pregnancy has been a mechanistic pathway implicated in autism development, yet few studies have examined this association directly. Here, we examined the association of prenatal levels of 8-iso-PGF2α, a widely used measure of oxidative stress, and several neurodevelopmental outcomes related to autism in children. Participants included 169 mother-child pairs from the Early Autism Risk Longitudinal Investigation (EARLI), which enrolled mothers who had an autistic child from a previous pregnancy and followed them through a subsequent pregnancy and until that child reached age 3 years. Maternal urine samples were collected during the second trimester of pregnancy and were later measured for levels of isoprostanes. Child neurodevelopmental assessments included the Mullen Scales of Early Learning (MSEL), the Social Responsiveness Scale (SRS), and the Vineland Adaptive Behavior Scale (VABS), and were conducted around 36 months of age. Primary analyses examined associations between interquartile range (IQR) increases in 8-iso-PGF2α levels, and total composite scores from each assessment using quantile regression. In adjusted analyses, we did not observe statistically significant associations, though estimates suggested modestly lower cognitive scores (β for MSEL = -3.68, 95% CI: -10.09, 2.70), and minor increases in autism-related trait scores (β for SRS T score = 1.68, 95% CI: -0.24, 3.60) with increasing 8-iso-PGF2α. These suggestive associations between decreased cognitive scores and increased autism-related traits with increasing prenatal oxidative stress point to the need for continued investigation in larger samples of the role of oxidative stress as a mechanistic pathway in autism and related neurodevelopmental outcomes.

Rates of family history of autism and ADHD varies with recruitment approach and socio-economic status

Family history (FH) of autism and ADHD is not often considered during the recruitment process of developmental studies, despite high recurrence rates. We looked at the rate of autism or ADHD amongst family members of young children (9 to 46 months) in three UK-based samples (N = 1055) recruited using different methods. The rate of FH-autism or FH-ADHD was 3%-9% for diagnosed cases. The rate was highest in the sample recruited through an online participant pool, which also consisted of the most socio-economically diverse families. Lower parental education and family income were associated with higher rates of FH-ADHD and lower parental education with increased FH-autism. Thus, recruitment strategies have a meaningful impact on neurodiversity and the conclusions and generalizations that can be drawn. Specifically, recruitment using crowdsourcing websites could create a sample that is more representative of the wider population, compared to those recruited through university-related volunteer databases and social media.

Clinical, socio-demographic, and parental correlates of early autism traits in a community cohort of toddlers

Identifying factors linked to autism traits in the general population may improve our understanding of the mechanisms underlying divergent neurodevelopment. In this study we assess whether factors increasing the likelihood of childhood autism are related to early autistic trait emergence, or if other exposures are more important. We used data from 536 toddlers from London (UK), collected at birth (gestational age at birth, sex, maternal body mass index, age, parental education, parental language, parental history of neurodevelopmental conditions) and at 18 months (parents cohabiting, measures of socio-economic deprivation, measures of maternal parenting style, and a measure of maternal depression). Autism traits were assessed using the Quantitative Checklist for Autism in Toddlers (Q-CHAT) at 18 months. A multivariable model explained 20% of Q-CHAT variance, with four individually significant variables (two measures of parenting style and two measures of socio-economic deprivation). In order to address variable collinearity we used principal component analysis, finding that a component which was positively correlated with Q-CHAT was also correlated to measures of parenting style and socio-economic deprivation. Our results show that parenting style and socio-economic deprivation correlate with the emergence of autism traits at age 18 months as measured with the Q-CHAT in a community sample.

The research landscape concerning environmental factors in neurodevelopmental disorders: Endocrine disrupters and pesticides-A review

In recent years, environmental epidemiology and toxicology have seen a growing interest in the environmental factors that contribute to the increased prevalence of neurodevelopmental disorders, with the purpose of establishing appropriate prevention strategies. A literature review was performed, and 192 articles covering the topic of endocrine disruptors and neurodevelopmental disorders were found, focusing on polychlorinated biphenyls, polybrominated diphenyl ethers, bisphenol A, and pesticides. This study contributes to analyzing their effect on the molecular mechanism in maternal and infant thyroid function, essential for infant neurodevelopment, and whose alteration has been associated with various neurodevelopmental disorders. The results provide scientific evidence of the association that exists between the environmental neurotoxins and various neurodevelopmental disorders. In addition, other possible molecular mechanisms by which pesticides and endocrine disruptors may be associated with neurodevelopmental disorders are being discussed.

Potential Mechanisms Underlying Suicidality in Autistic People with Attention Deficit/Hyperactivity Disorder: Testing Hypotheses from the Interpersonal Theory of Suicide

Background

Autistic people with co-occurring attention deficit/hyperactivity disorder (ADHD) appear to be at heightened risk of suicide. To understand why, we explored two explanatory mechanisms from the interpersonal theory of suicide: first, that co-occurring ADHD might be associated with greater risk through greater thwarted belongingness and perceived burdensomeness and, secondly, that hyperactive/impulsive features might incur additional risk through their association with painful and provocative events, which are suggested to create "capability" for suicide.

Methods

Autistic adults (n = 314) completed an online survey including measures of thwarted belongingness, perceived burdensomeness, painful and provocative events, acquired capability for suicide, and ADHD features. Creating an overall index of likely ADHD, we examined associations between likely ADHD, suicide ideation, and lifetime suicide attempts through the parallel mediators of thwarted belongingness, perceived burdensomeness, anxiety, and depression. In several models, we then examined hyperactive, impulsive, and inattentive features as predictors of exposure to painful and provocative events and subsequent capability for suicide, and examined whether these two variables, sequentially or individually, mediated an association with lifetime suicide attempts.

Results

Likely ADHD was associated with past-year suicide ideation through greater depression and perceived burdensomeness, which also mediated its association with more suicide attempts. Hyperactive and impulsive features were associated with exposure to painful and provocative events and through this acquired suicide capability. Both features were associated with more numerous suicide attempts through these two mediators sequentially, and through exposure to painful and provocative events alone.

Conclusions

These data suggest that suicidality in autistic people with ADHD may be partially related to perceived burdensomeness and to acquired suicide capability after exposure to painful and provocative events. However, as we observed a pathway to suicidality associated with painful and provocative events alone, it is likely that there are also other explanatory mechanisms for the influence of traumatic events on suicide risk.

Brain-charting autism and attention deficit hyperactivity disorder reveals distinct and overlapping neurobiology

Background

Autism and attention deficit hyperactivity disorder (ADHD) are heterogeneous neurodevelopmental conditions with complex underlying neurobiology. Despite overlapping presentation and sex-biased prevalence, autism and ADHD are rarely studied together, and sex differences are often overlooked. Normative modelling provides a unified framework for studying age-specific and sex-specific divergences in neurodivergent brain development.

Methods

Here we use normative modelling and a large, multi-site neuroimaging dataset to characterise cortical anatomy associated with autism and ADHD, benchmarked against models of typical brain development based on a sample of over 75,000 individuals. We also examined sex and age differences, relationship with autistic traits, and explored the co-occurrence of autism and ADHD (autism+ADHD).

Results

We observed robust neuroanatomical signatures of both autism and ADHD. Overall, autistic individuals showed greater cortical thickness and volume localised to the superior temporal cortex, whereas individuals with ADHD showed more global effects of cortical thickness increases but lower cortical volume and surface area across much of the cortex. The autism+ADHD group displayed a unique pattern of widespread increases in cortical thickness, and certain decreases in surface area. We also found evidence that sex modulates the neuroanatomy of autism but not ADHD, and an age-by-diagnosis interaction for ADHD only.

Conclusions

These results indicate distinct cortical differences in autism and ADHD that are differentially impacted by age, sex, and potentially unique patterns related to their co-occurrence.

Three year outcomes in infants with a family history of autism and/or attention deficit hyperactivity disorder

Background

Most research on early outcomes in infants with a family history (FH) of autism has focussed on categorically defined autism, although some have language and developmental delays. Less is known about outcomes in infants with a FH of attention deficit hyperactivity disorder (ADHD).

Methods

Infants with and without a FH of autism and/or ADHD, due to a first-degree relative with either or both conditions, were recruited at 5 or 10 months. Three year outcomes were characterised using latent profile analysis (LPA) across measures of cognitive ability, adaptive functioning and autism, ADHD and anxiety traits (n = 131). We additionally ran an LPA using only autism and ADHD measures, and the broader LPA in an independent cohort (n = 139) and in both cohorts combined (n = 270).

Results

A Low Developmental Level + High Behavioural Concerns class had elevated autism, ADHD and anxiety scores, low cognitive and adaptive function, and included all but one child with autism. A Low Developmental Level + Typical Behaviour class had average cognitive ability and typical behaviour but low adaptive function. A Typical Developmental Level + Some Behavioural Concerns class had average cognitive and adaptive function but slightly elevated behaviour scores. A High Developmental Level + Typical Behaviour class had above average cognitive ability and typical behaviour. All four LPAs identified classes characterised by combinations of either, or both, Low Development Level and elevated behaviour scores, as well as a typically developing class. No classes had elevated autism or ADHD traits in isolation.

Conclusions

Some infants with a FH of autism or ADHD have atypical developmental and behavioural outcomes, but do not show strong autism or ADHD traits in isolation. The field needs to recalibrate aims and methods to embrace the broader transdiagnostic pattern of outcomes seen in these infants.

Diversity and Classification of Genetic Variations in Autism Spectrum Disorder

Autism spectrum disorder (ASD) is a neurodevelopmental condition with symptoms that affect the whole personality and all aspects of life. Although there is a high degree of heterogeneity in both its etiology and its characteristic behavioral patterns, the disorder is well-captured along the autistic triad. Currently, ASD status can be confirmed following an assessment of behavioral features, but there is a growing emphasis on conceptualizing autism as a spectrum, which allows for establishing a diagnosis based on the level of support need, free of discrete categories. Since ASD has a high genetic predominance, the number of genetic variations identified in the background of the condition is increasing exponentially as genetic testing methods are rapidly evolving. However, due to the huge amount of data to be analyzed, grouping the different DNA variations is still challenging. Therefore, in the present review, a multidimensional classification scheme was developed to accommodate most of the currently known genetic variants associated with autism. Genetic variations have been grouped according to six criteria (extent, time of onset, information content, frequency, number of genes involved, inheritance pattern), which are themselves not discrete categories, but form a coherent continuum in line with the autism spectrum approach.

Maternal sleep disturbances during late pregnancy and child neuropsychological and behavioral development in early childhood

The present study aims to explore the association of maternal sleep disturbances during late pregnancy on child neuropsychological and behavioral development in preschool years. The study included 638 mother-child pairs from the prospective Rhea mother-child cohort in Crete, Greece. Information on antenatal sleep disturbances was collected through a computer-assisted interview. Children's neuropsychological and behavioral development was assessed using the McCarthy Scales of Children's Abilities (MSCA), the Attention-Deficit Hyperactivity Disorder Test (ADHDT), and the Strengths and Difficulties Questionnaire (SDQ). Multivariate analysis showed that maternal sleep duration less than 8 h was associated with reduced scores in the general cognitive scale (β = -2.28, 95% CI -4.54, -0.02, R2 = 0.417) and memory span (β = -3.24, 95% CI -5.72, -0.77, R2 = 0.304), while mild-severe daytime sleepiness was associated with reduced scores in the memory scale (β = -5.42, 95% CI -10.47, -0.37, R2 = 0.304), memory span (β = -5.44, 95% CI -10.68, -0.21, R2 = 0.304), nd functions of posterior cortex (β = -5.55, 95% CI -10.40, -0.70, R2 = 0.393) of MSCA. Snoring in late pregnancy was related to higher child hyperactivity scores in SDQ (β = 1.05, 95% CI 0.16, 1.95, R2 = 0.160). An interaction between child sex and maternal sleep duration in response to ADHD symptoms was also found (p for interaction < 0.05). Stratified analysis revealed increased hyperactivity, inattention, and ADHD total scores for girls of mothers with sleep duration less than 8 h. Maternal sleep disturbances during pregnancy may be associated with impaired child neuropsychological and behavioral development during the preschool years. Early detection and intervention is necessary to reduce sleep disturbances habits in pregnancy and improve child neurodevelopment.

Dopaminergic cell protection and alleviation of neuropsychiatric disease symptoms by VMAT2 expression through the class I HDAC inhibitor TC-H 106

The importance of vesicular monoamine transporter 2 (VMAT2) in dopamine regulation, which is considered crucial for neuropsychiatric disorders, is currently being studied. Moreover, the development of disease treatments using histone deacetylase (HDAC) inhibitors (HDACi) is actively progressing in various fields. Recently, research on the possibility of regulating neuropsychiatric disorders has been conducted. In this study, we evaluated whether VMAT2 expression increased by an HDACi can fine-tune neuropsychotic behavior, such as attention deficit hyperactivity disorder (ADHD) and protect against the cell toxicity through oxidized dopamine. First, approximately 300 candidate HDACi compounds were added to the SH-SY5Y dopaminergic cell line to identify the possible changes in the VMAT2 expression levels, which were measured using quantitative polymerase chain reaction. The results demonstrated, that treatment with pimelic diphenylamide 106 (TC-H 106), a class I HDACi, increased VMAT2 expression in both the SH-SY5Y cells and mouse brain. The increased VMAT2 expression induced by TC-H 106 alleviated the cytotoxicity attributed to 6-hydroxydopamine (6-OHDA) or 1-methyl-4-phenylpyridinium (MPP+ ) and free dopamine treatment. Moreover, dopamine concentrations, both intracellularly and in the synaptosomes, were significantly elevated by increased VMAT2 expression. These results suggest that dopamine concentration regulation by VMAT2 expression induced by TC-H 106 could alter several related behavioral aspects that was confirmed by attenuation of hyperactivity and impulsivity, which were major characteristics of animal model showing ADHD-like behaviors. These results indicate that HDACi-increased VMAT2 expression offers sufficient protections against dopaminergic cell death induced by oxidative stress. Thus, the epigenetic approach could be considered as therapeutic candidate for neuropsychiatric disease regulation.

Association between cumulative psychosocial adversity in the family and ADHD and autism: a family-based cohort study

Cumulative exposure to psychosocial adversity at an early age has been shown to be a risk factor for attention-deficit hyperactivity disorder (ADHD) and autism that often co-occur. However, it is not clear if this association reflects a causal effect or familial confounding. We aimed to assess whether cumulative psychosocial adversity in the family increases the risk for ADHD and autism in offspring while accounting for unmeasured familial confounding. We used a population-based cohort of 1,877,901 individuals born in Sweden between 1990 and 2009. Participants were followed from the age of 3 until 2013, with a median follow up time of 13.8 years. We created a cumulative index based on 7 psychosocial adversity factors. We used Cox regression to estimate the hazard ratios (HRs) relating neurodevelopmental conditions to cumulative psychosocial adversity. To address familial confounding, the analyses were repeated in groups of relatives of different kinship: siblings and half-siblings and cousins. A dose-response relationship was observed between cumulative exposure to psychosocial adversity and ADHD at a general population level (covariate adjusted HRs (aHRs) with 95% confidence intervals ranged from 1.55 [one adversity; 1.53-1.58] to 2.65 [ ≥ 4 adversities; 1.98-3.54]). No clear dose-response relation was seen for autism (aHRs ranged from 1.04 [.59-1.84] to 1.37 [1.30-1.45]). HRs of ADHD and autism decreased with increasing level of kinship in the analysis of relatives. Cumulative exposure to psychosocial adversity was associated with both ADHD and autism in the general population, these associations were partly explained by unmeasured familial confounding between relatives. This highlights the need for using family-based designs in studies of psychosocial adversity and ADHD and autism.

Using the Infant Sibling-Design to Explore Associations Between Autism and ADHD Traits in Probands and Temperament in the Younger Siblings

The purpose of the current study was to use the infant sibling design to explore whether proband traits of autism and ADHD could provide information about their infant sibling's temperament. This could help us to gain information about the extent to which infant temperament traits are differentially associated with autism and ADHD traits. We used parent-ratings of autistic traits and ADHD traits (CRS-3) in older siblings diagnosed with autism (age range 4 to 19 years), and their infant siblings' temperament traits (IBQ) at 9 months of age in 216 sibling pairs from two sites (BASIS, UK, and EASE, Sweden) to examine associations across siblings. We found specific, but modest, associations across siblings after controlling for sex, age, developmental level and site. Proband autistic traits were specifically related to low levels of approach in the infant siblings, with infant developmental level explaining part of the variance in infant approach. Proband ADHD traits were specifically related to high levels of infant activity even after controlling for covariates. Our findings suggest that proband traits of autism and ADHD carry information for infant sibling's temperament, indicating that inherited liability may influence early emerging behaviours in infant siblings. The impact of sex, age, developmental level and site are discussed.

Delineating early developmental pathways to ADHD: Setting an international research agenda

Background

Attention-deficit/hyperactivity disorder (ADHD) is a prevalent, impairing, and highly heritable condition typically diagnosed in middle childhood. However, it is now recognized that symptoms emerge much earlier in development. Research focused on understanding-using multiple units of analysis-the cascade of early-life (i.e., prenatal-infant-toddler) developmental changes that will later emerge as ADHD has the potential to transform early identification, prevention, and intervention. To this end, we introduce the recently established Early ADHD Consortium, an international network of investigators engaged in prospective, longitudinal studies of risk for ADHD beginning early in life, conducted within a developmental framework, and which incorporate multimethod approaches. This network seeks to harmonize measures and methodological approaches to increase the potential for data sharing and subsequent impact.

Methods

This perspective paper highlights the importance of investigating pre-diagnostic markers of ADHD, and potential models and mechanisms of ADHD risk and development, with the long-term objective of facilitating development of preemptive interventions that will minimize the impact of ADHD symptoms on everyday functioning and maximize health and developmental outcomes.

Results

We selectively describe key challenges and questions for this field related to theoretical models and developmental mechanisms in ADHD and recommend next steps for the science, including methodological, measurement, and study design considerations. We then describe potential implications for preemptive intervention development. We conclude by considering other issues including ethical concerns and the critical value of incorporating stakeholder input.

Conclusions

It is hoped that this perspective puts forth a research agenda that will enhance collaborative efforts and accelerate progress in understanding developmental mechanisms and the early ADHD phenotype, with implications for early intervention enhancement of healthy development for infants, young children, and their families.

The Oregon ADHD-1000: A new longitudinal data resource enriched for clinical cases and multiple levels of analysis

The fields of developmental psychopathology, developmental neuroscience, and behavioral genetics are increasingly moving toward a data sharing model to improve reproducibility, robustness, and generalizability of findings. This approach is particularly critical for understanding attention-deficit/hyperactivity disorder (ADHD), which has unique public health importance given its early onset, high prevalence, individual variability, and causal association with co-occurring and later developing problems. A further priority concerns multi-disciplinary/multi-method datasets that can span different units of analysis. Here, we describe a public dataset using a case-control design for ADHD that includes: multi-method, multi-measure, multi-informant, multi-trait data, and multi-clinician evaluation and phenotyping. It spans > 12 years of annual follow-up with a lag longitudinal design allowing age-based analyses spanning age 7-19 + years with a full age range from 7 to 21. Measures span genetic and epigenetic (DNA methylation) array data; EEG, functional and structural MRI neuroimaging; and psychophysiological, psychosocial, clinical and functional outcomes data. The resource also benefits from an autism spectrum disorder add-on cohort and a cross sectional case-control ADHD cohort from a different geographical region for replication and generalizability. Datasets allowing for integration from genes to nervous system to behavior represent the "next generation" of researchable cohorts for ADHD and developmental psychopathology.

Annual Research Review: Perspectives on progress in ADHD science - from characterization to cause

The science of attention-deficit/hyperactivity disorder (ADHD) is motivated by a translational goal - the discovery and exploitation of knowledge about the nature of ADHD to the benefit of those individuals whose lives it affects. Over the past fifty years, scientific research has made enormous strides in characterizing the ADHD condition and in understanding its correlates and causes. However, the translation of these scientific insights into clinical benefits has been limited. In this review, we provide a selective and focused survey of the scientific field of ADHD, providing our personal perspectives on what constitutes the scientific consensus, important new leads to be highlighted, and the key outstanding questions to be addressed going forward. We cover two broad domains - clinical characterization and, risk factors, causal processes and neuro-biological pathways. Part one focuses on the developmental course of ADHD, co-occurring characteristics and conditions, and the functional impact of living with ADHD - including impairment, quality of life, and stigma. In part two, we explore genetic and environmental influences and putative mediating brain processes. In the final section, we reflect on the future of the ADHD construct in the light of cross-cutting scientific themes and recent conceptual reformulations that cast ADHD traits as part of a broader spectrum of neurodivergence.

Individual-Level Risk and Resilience Factors Associated with Mental Health in Siblings of Individuals with Neurodevelopmental Conditions: A Network Analysis

Siblings of individuals with neurodevelopmental conditions (NDCs) are exposed to unique family environments and experience a range of psychosocial risk and resilience factors. Networks of self-reported risk, resilience, and neuropsychiatric variables were estimated for siblings of individuals with (n = 235) and without (n = 480) NDCs (N = 715, mean age 22.40 years, 76% female, 74% White Caucasian). The NDC group reported more depressive (g = 0.39) and anxious (g = 0.43) symptoms than controls, and 71.5% of the NDC group reported at least one neuropsychiatric diagnosis compared to 36.9% of controls. Self-reported sleep and post-traumatic stress disorders were high amongst NDC siblings. Everyday executive functioning difficulties (cognitive inflexibility, hyperactivity/impulsivity) and emotion dysregulation were the most influential transdiagnostic risk factors for poorer functioning within the NDC group network.

Psychopathology of attention deficit/hyperactivity disorder: from an inflammatory perspective

Background

Attention deficit/hyperactivity disorder (ADHD) is a neurodevelopmental disorder characterized by inattentiveness, hyperactivity and impulsivity, which may affect one’s cognitive and psychosocial functioning. This review gives an overview of ADHD, particularly from an aetiological and clinical perspective. It also critically examines current evidence on the role of inflammation in ADHD and consolidates key findings in this area of research.

Results

The exact cause of ADHD remains unknown, and the aetiology of the disorder is believed to be multifactorial. Numerous genetic and environmental factors have been linked to the development of ADHD. Like many psychiatric disorders, ADHD has been associated with inflammation that occurs locally and peripherally. A growing body of evidence shows that maternal inflammatory status during pregnancy is associated with diagnosis of ADHD in the offspring, whereas oxidative stress, inflammatory biochemical markers and immune-mediated diseases have been observed in individuals with ADHD.

Conclusions

The underlying inflammatory processes and mechanisms in ADHD are not clearly understood. Therefore, further exploration is warranted in future research. This has clinical implications as inflammation may be a potential target in the treatment of ADHD.

Developmental and mental health risks among siblings of patients with autism spectrum disorder: a nationwide study

Studies have suggested that unaffected siblings of patients with autism spectrum disorder (ASD) have some other neurodevelopmental abnormalities. However, the risks of mental and developmental disorders have rarely been investigated among unaffected siblings. Using Taiwan's National Health Insurance Research Database, 1304 unaffected siblings born between 1980 and 2010 with ASD probands and 13,040 age-/sex-/family structure-matched controls were included in our study and followed up from 1996 or birth to the end of 2011. Developmental delay, language delay, developmental coordination disorder, attention-deficit hyperactivity disorder (ADHD), anxiety disorders, disruptive behavior disorders, unipolar disorder, and bipolar disorder were identified during the follow-up period. Unaffected siblings were more likely to develop any developmental delay, developmental speech or language disorder, developmental coordination disorder, intelligence disability, ADHD, anxiety disorders, unipolar depression, and disruptive behavior disorders compared with the control group. Brothers of patients with ASD had a higher risk of neurodevelopmental abnormalities, ADHD, anxiety disorders, and disruptive behavior disorders; sisters were prone to having neurodevelopmental abnormalities, ADHD, anxiety disorders, unipolar depression, and disruptive behavior disorders. Unaffected siblings of patients with ASD were prone to developing any developmental or mental disorder later in life. Clinicians and public health officials should pay more attention to the developmental condition and mental health of unaffected siblings of patients with ASD.

Altered theta-beta ratio in infancy associates with family history of ADHD and later ADHD-relevant temperamental traits

BACKGROUND

Uncovering the neural mechanisms that underlie symptoms of attention deficit hyperactivity disorder (ADHD) requires studying brain development prior to the emergence of behavioural difficulties. One new approach to this is prospective studies of infants with an elevated likelihood of developing ADHD.

METHODS

We used a prospective design to examine an oscillatory electroencephalography profile that has been widely studied in both children and adults with ADHD - the balance between lower and higher frequencies operationalised as the theta-beta ratio (TBR). In the present study, we examined TBR in 136 10-month-old infants (72 male and 64 female) with/without an elevated likelihood of developing ADHD and/or a comparison disorder (Autism Spectrum Disorder; ASD).

RESULTS

Infants with a first-degree relative with ADHD demonstrated lower TBR than infants without a first-degree relative with ADHD. Further, lower TBR at 10 months was positively associated with temperament dimensions conceptually related to ADHD at 2 years. TBR was not altered in infants with a family history of ASD.

CONCLUSIONS

This is the first demonstration that alterations in TBR are present prior to behavioural symptoms of ADHD. However, these alterations manifest differently than those sometimes observed in older children with an ADHD diagnosis. Importantly, altered TBR was not seen in infants at elevated likelihood of developing ASD, suggesting a degree of specificity to ADHD. Taken together, these findings demonstrate that there are brain changes associated with a family history of ADHD observable in the first year of life.

Click-evoked auditory brainstem responses and autism spectrum disorder: a meta-analytic investigation of disorder specificity

BACKGROUND

Click-evoked auditory brainstem response (ABR) alterations are associated with autism spectrum disorder (ASD), but the specificity of these findings to the disorder is unclear. We therefore performed a meta-analysis on ABRs and attention-deficit/hyperactivity disorder (ADHD), a neurodevelopmental disorder that shares some etiologic and symptom overlap with ASD.

METHODS

Seven papers compared ABR latency components (I, III, V, I-III, III-V, and I-V) between participants with and without ADHD. We used random-effects regression to generate component-specific estimates (Hedges's g) that adjusted for study sample sizes and the number of studies contributing to each estimate. We compared these estimates to our recently published meta-analysis of ABRs and ASD.

RESULTS

All ADHD studies employed cross-sectional designs. ADHD was associated with longer latencies for waves III and V (g = 0.6, 95% confidence interval (CI) 0.3, 1.0 and g = 0.6, 95% CI 0.3, 0.9) and waves I-III and I-V (g = 0.7, 95% CI 0.2, 1.3 and g = 0.6, 95% CI 0.3, 1.0). Effect sizes from the ASD and ADHD meta-analyses did not differ from each other.

CONCLUSIONS

Similar patterns of ABR alterations are observed in ADHD and ASD. However, studies rarely screen for middle ear dysfunction or hearing loss and rely upon cross-sectional designs. Addressing these issues will inform the viability of ABRs as a prognostic and/or etiologic biomarker for these disorders.

IMPACT

Click-evoked ABR alterations are associated with ASD, but the specificity of these findings to the disorder is unclear. We therefore performed a meta-analysis of the association between ABRs and ADHD, a disorder that shares some etiologic and symptom overlap with ASD. ADHD was associated with longer ABR latencies for several components. These components are identical to those implicated in ASD. Effect sizes were similar in magnitude across disorders. The viability of ABRs as prognostic and/or etiologic biomarkers for neurodevelopmental risk requires addressing limitations in the literature (e.g., cross-sectional data, non-standardized ABR protocols, minimal characterization of symptom heterogeneity).

Elevated symptoms of executive dysfunction predict lower adaptive functioning in 3-year-olds with autism spectrum disorder

Executive functioning (EF) deficits co-occur frequently with autism spectrum disorder (ASD) and have a long-term detrimental impact on quality of life of children and their families. Timely identification of risk for EF vulnerabilities may hasten access to early intervention and alleviate their long-term consequences. This study examines (1) if EF deficits are elevated in toddlers with ASD compared to nonautistic siblings of children with ASD, typically developing (TYP) toddlers, and toddlers with atypical developmental presentation; and (2) if EF deficits have a detrimental effect on adaptive functioning in ASD. Participants were recruited between September 2014 and October 2019 and included 73 toddlers with ASD, 33 nonautistic siblings of children with ASD, 35 toddlers with atypical development, and 28 TYP toddlers matched on chronological age (M = 39.01 months, SD = 3.11). EF deficits were measured using the BRIEF-P; adaptive skills were measured using the VABS-II. Whenever appropriate, analyses were controlled for MSEL verbal and nonverbal developmental quotient, ADOS-2 autism severity scores, and sex. Analyses revealed that toddlers with ASD exhibited elevated BRIEF-P scores across all domains compared to each of the three comparison groups. Higher BRIEF-P scores were associated with lower adaptive social, communication, and daily living skills while controlling for symptom severity, verbal and nonverbal functioning, and sex. In conclusion, marked vulnerabilities in EF are already present in 3-year-old toddlers with ASD and are predictive of the level of adaptive functioning in ASD. EF vulnerabilities in toddlers should be targeted for intervention to improve long-term outcomes in ASD. LAY SUMMARY: Many children with autism experience vulnerabilities in executive functioning (EF), which may include challenges with inhibition, working memory, cognitive flexibility, and planning. The study shows that these vulnerabilities can already be detected at age three and that their presence is linked with lower social, communication, and daily living skills. Screening children with ASD for EF challenges and helping those who have difficulties may improve their long-term outcomes.

Association between birth weight and neurodevelopmental disorders assessed using the Korean National Health Insurance Service claims data

The risk of neurodevelopmental disorders in low birth weight (LBW) infants has gained recognition but remains debatable. We investigated the risk of attention-deficit/hyperactivity disorder (ADHD) and autism spectrum disorder (ASD) in school-aged children according to their birth weight. We conducted a retrospective cohort study using the Korean National Health Insurance claims data of 2,143,652 children who were born between 2008 and 2012. Gestational age of infants was not available; thus, outcomes were not adjusted with it. Not only infants with birth weights of < 1.5 kg, but also 2.0–2.4 kg and 1.5–1.9 kg were associated with having ADHD; odds ratio (OR), 1.41 (95% confidence interval [CI] 1.33–1.50), and 1.49 (95% CI 1.33–1.66), respectively. The OR in infants with birth weights of 2.0–2.4 kg and 1.5–1.9 kg was 1.91 (95% CI 1.79–2.05) and 3.25 (95% CI 2.95–3.59), respectively, indicating increased odds of having ASD. Subgroup analysis for children without perinatal diseases showed similar results. In this national cohort, infants with birth weights of < 2.5 kg were associated with ADHD and ASD, regardless of perinatal history. Children born with LBW need detailed clinical follow-up.

ADHD and autism symptoms in youth: a network analysis

BACKGROUND

Previous research investigating the overlap between attention-deficit/hyperactivity disorder (ADHD) and autism spectrum disorder (henceforth, autism) symptoms in population samples have relied on latent variable modeling in which averaged scores representing dimensions were derived from observed symptoms. There are no studies evaluating how ADHD and autism symptoms interact at the level of individual symptom items.

METHODS

We aimed to address this gap by performing a network analysis on data from a school survey of children aged 6-17 years old (N = 7,405). ADHD and autism symptoms were measured via parent-report on the Swanson, Nolan, Pelham-IV questionnaire and the Childhood Autism Spectrum test, respectively.

RESULTS

A relatively low interconnectivity between ADHD and autism symptoms was found with only 10.06% of possible connections (edges) between one ADHD and one autism symptoms different than zero. Associations between ADHD and autism symptoms were significantly weaker than those between two symptoms pertaining to the same construct. Select ADHD symptoms, particularly those presenting in social contexts (e.g. 'talks excessively', 'does not wait turn'), showed moderate-to-strong associations with autism symptoms, but some were considered redundant to autism symptoms.

CONCLUSIONS

The present findings indicate that individual ADHD and autism symptoms are largely segregated in accordance with diagnostic boundaries corresponding to these conditions in children and adolescents from the community. These findings could improve our clinical conceptualization of ADHD and autism and guide advancements in diagnosis and treatment.

INTERSTAARS: Attention training for infants with elevated likelihood of developing ADHD: A proof-of-concept randomised controlled trial

Attention-deficit/hyperactivity disorder (ADHD) is first diagnosed during middle childhood, when patterns of difficulty are often established. Pre-emptive approaches that strengthen developing cognitive systems could offer an alternative to post-diagnostic interventions. This proof-of-concept randomised controlled trial (RCT) tested whether computerised gaze-based attention training is feasible and improves attention in infants liable to develop ADHD. Forty-three 9- to 16-month-old infants with a first-degree relative with ADHD were recruited (11/2015-11/2018) at two UK sites and randomised with minimisation by site and sex to receive 9 weekly sessions of either (a) gaze-contingent attention training (intervention; n = 20); or (b) infant-friendly passive viewing of videos (control, n = 23). Sessions were delivered at home with blinded outcome assessments. The primary outcome was a composite of attention measures jointly analysed via a multivariate ANCOVA with a combined effect size (ES) from coefficients at baseline, midpoint and endpoint (Registration: ISRCTN37683928 ). Uptake and compliance was good but intention-to-treat analysis showed no significant differences between 20 intervention and 23 control infants on primary (ES -0.4, 95% CI -0.9 to 0.2; Complier-Average-Causal Effect ES -0.6, 95% CI -1.6 to 0.5) or secondary outcomes (behavioural attention). There were no adverse effects on sleep but a small increase in post-intervention session fussiness. Although feasible, there was no support for short-term effects of gaze-based attention training on attention skills in early ADHD. Longer-term outcomes remain to be assessed. The study highlights challenges and opportunities for pre-emptive intervention approaches to the management of ADHD.

Can Familial Risk for ADHD Be Detected in the First Two Years of Life?

Objective: We evaluated trajectories of attention-deficit/hyperactivity (ADHD)-relevant behaviors in a sample of infants at high and low familial risk for ADHD who were prospectively evaluated at 12, 18, and 24 months of age.Method: Participants included 43 infants at risk for ADHD based on family history (i.e., diagnosed first-degree relative) and 40 low-risk infants (i.e., no family history of ADHD). Instances of inattention, out-of-seat, and grabbing behavior were coded from video; analogous constructs were rated by examiners unaware of familial risk status after completing structured standardized assessments with the infants/toddlers. At the end of each study visit, examiners solicited parents' concerns about their child's behavior. Differences in ADHD-related behaviors and parent concerns were examined between 12 and 24 months of age.Results: Infants with an older sibling or parent diagnosed with ADHD were distinguishable from infants with no family history of ADHD as early as 12 months of age based on directly observed and examiner reports of behavior, particularly with respect to hyperactive-impulsive behavior. Parents of infants at familial risk for ADHD also reported significantly more behavior/temperament concerns as early as 12 months of age compared to parents of infants at low risk for ADHD.Conclusions: These findings highlight the ability to detect genetic liability for ADHD by the end of the first year of life, suggesting that well-designed family risk studies of ADHD are feasible and may be clinically valuable. They also suggest the potential for earlier detection of risk for ADHD than has previously been possible.

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.

Practitioner Review: Pharmacological treatment of attention-deficit/hyperactivity disorder symptoms in children and youth with autism spectrum disorder: a systematic review and meta-analysis

BACKGROUND

Clinically significant attention-deficit/hyperactivity disorder (ADHD) symptoms are common and impairing in children and youth with autism spectrum disorder(ASD). The aim of this systematic review and meta-analysis was to (a) evaluate the efficacy and safety of pharmacotherapy for the treatment of ADHD symptoms in ASD and (b) distil findings for clinical translation.

METHODS

We searched electronic databases and clinical trial registries (1992 onwards). We selected randomized controlled trials conducted in participants <25 years of age, diagnosed with ASD that evaluated ADHD outcomes (hyperactivity/impulsivity and inattention) following treatment with stimulants (methylphenidate or amphetamines), atomoxetine, alpha-2 adrenergic receptor agonists, antipsychotics, tricyclic antidepressants, bupropion, modafinil, venlafaxine, or a combination, in comparison with placebo, any of the listed medications, or behavioral therapies. Data were pooled using a random-effects model.

RESULTS

Twenty-five studies (4 methylphenidate, 4 atomoxetine, 1 guanfacine, 14 antipsychotic, 1 venlafaxine, and 1 tianeptine) were included. Methylphenidate reduced hyperactivity (parent-rated: standardized mean difference [SMD] = -.63, 95%CI = -.95,-.30; teacher-rated: SMD = -.81, 95%CI = -1.43,-.19) and inattention (parent-rated: SMD = -.36, 95%CI = -.64,-.07; teacher-rated: SMD = -.30, 95%CI = -.49,-.11). Atomoxetine reduced inattention (parent-rated: SMD = -.54, 95%CI = -.98,-.09; teacher/investigator-rated: SMD = -0.38, 95%CI = -0.75, -0.01) and parent-rated hyperactivity (parent-rated: SMD = -.49, 95%CI = -.76,-.23; teacher-rated: SMD = -.43, 95%CI = -.92, .06). Indirect evidence for significant reductions in hyperactivity with second-generation antipsychotics was also found. Quality of evidence for all interventions was low/very low. Methylphenidate was associated with a nonsignificant elevated risk of dropout due to adverse events.

CONCLUSIONS

Direct pooled evidence supports the efficacy and tolerability of methylphenidate or atomoxetine for treatment of ADHD symptoms in children and youth with ASD. The current review highlights the efficacy of standard ADHD pharmacotherapy for treatment of ADHD symptoms in children and youth with ASD. Consideration of the benefits weighed against the limitations of safety/efficacy data and lack of data evaluating long-term continuation is undertaken to help guide clinical decision-making regarding treatment of co-occurring ADHD symptoms in children and youth with ASD.

Clinical and Translational Implications of an Emerging Developmental Substructure for Autism

A vast share of the population-attributable risk for autism relates to inherited polygenic risk. A growing number of studies in the past five years have indicated that inherited susceptibility may operate through a finite number of early developmental liabilities that, in various permutations and combinations, jointly predict familial recurrence of the convergent syndrome of social communication disability that defines the condition. Here, we synthesize this body of research to derive evidence for a novel developmental substructure for autism, which has profound implications for ongoing discovery efforts to elucidate its neurobiological causes, and to inform future clinical and biomarker studies, early interventions, and personalized approaches to therapy.

How Family Histories Can Inform Research About Germ Cell Exposures: The Example of Autism

Throughout the scientific literature, heritable traits are routinely presumed to be genetic in origin. However, as emerging evidence from the realms of genetic toxicology and epigenomics demonstrate, heritability may be better understood as encompassing not only DNA sequence passed down through generations, but also disruptions to the parental germ cells causing de novo mutations or epigenetic alterations, with subsequent shifts in gene expression and functions in offspring. The Beyond Genes conference highlighted advances in understanding these aspects at molecular, experimental and epidemiological levels. In this commentary I suggest that future research on this topic could be inspired by collecting parents' germ cell exposure histories, with particular attention to cases of families with multiple children suffering idiopathic disorders. In so doing I focus on the endpoint of autism spectrum disorders (ASD). Rates of this serious neurodevelopment disability have climbed around the world, a growing crisis that cannot be explained by diagnostic shifts. ASD's strong heritability has prompted a research program largely focused on DNA sequencing to locate rare and common variants, but decades of this gene-focused research have revealed surprisingly little about the molecular origins of the disorder. Based on my experience as the mother of two children with idiopathic autism, and as a research philanthropist and autism advocate, I suggest ways researchers might probe parental germ cell exposure histories to develop new hypotheses that may ultimately reveal sources of non-genetic heritability in a subset of idiopathic heritable pathologies.

Understanding ADHD: Toward an Innovative Therapeutic Intervention

Attention deficit hyperactivity disorder (ADHD) is a pervasive condition affecting persons across all age groups, although it is primarily diagnosed in children. This neurological condition affects behavior, learning, and social adjustment and requires specific symptomatic criteria to be fulfilled for diagnosis. ADHD may be treated with a combination of psychological or psychiatric therapeutic interventions, but it often goes unattended. People with ADHD face societal bias challenges that impact how they manage the disorder and how they view themselves. This paper summarizes the present state of understanding of this disorder, with particular attention to early diagnosis and innovative therapeutic intervention. Contemporary understanding of the mind-brain duality allows for innovative therapeutic interventions based on neurological stimulation. This paper introduces the concept of neurostimulation as a therapeutic intervention for ADHD and poses the question of the relationship between patient adherence to self-administered therapy and the aesthetic design features of the neurostimulation device. By fabricating devices that go beyond safety and efficacy to embrace the aesthetic preferences of the patient, it is proposed that there will be improvements in patient adherence to a device intended to address ADHD.

Genetic Overlap Between Attention Deficit/Hyperactivity Disorder and Autism Spectrum Disorder in SHANK2 Gene

Background: Recent findings indicated a high comorbidity between attention-deficit/hyperactivity disorder (ADHD) and autism spectrum disorder (ASD), as well as shared genetic influences on them. The latter might contribute at least partly to the former clinical scenario. This study aimed at investigating whether SHANK genes were potential pleiotropic genes to the two said disorders, underlying their genetic overlap.

Methods: This study recruited 298 boys with ADHD (including 256 family trios of 1 ADHD boy and his 2 biological parents), 134 boys with ASD, 109 boys with both ADHD and ASD, and 232 typically developing boys as community controls. They were aged between 6 and 11 years old.

Results: There was no significant difference in allele frequency of a number of single nucleotide polymorphisms (SNPs) in SHANK2/SHANK3 between the three clinical groups (ADHD, ASD, and ADHD + ASD) and between the two control groups (community controls and pseudo-controls), respectively. The three clinical groups and the two control groups were thus, respectively, combined. A comparison between the two aggregated samples identified significant evidence of disease association for three SHANK2 SNPs with both ADHD and ASD, even after multiple testing correction: rs11236616 (OR = 0.762, permuted p = 0.0376), rs7106631 (OR = 0.720, permuted p = 0.0034), and rs9888288 (OR = 0.770, permuted p = 0.0407). Comparisons among individual groups pointed to a similar trend of findings.

Conclusion:SHANK2 could be considered a potential pleiotropic gene underlying the genetic overlap between ADHD and ASD. This might contribute partly to their high comorbidity in the afflicted children.

Behavioural Measures of Infant Activity but Not Attention Associate with Later Preschool ADHD Traits

Mapping infant neurocognitive differences that precede later ADHD-related behaviours is critical for designing early interventions. In this study, we investigated (1) group differences in a battery of measures assessing aspects of attention and activity level in infants with and without a family history of ADHD or related conditions (ASD), and (2) longitudinal associations between the infant measures and preschool ADHD traits at 3 years. Participants (N = 151) were infants with or without an elevated likelihood for ADHD (due to a family history of ADHD and/or ASD). A multi-method assessment protocol was used to assess infant attention and activity level at 10 months of age that included behavioural, cognitive, physiological and neural measures. Preschool ADHD traits were measured at 3 years of age using the Child Behaviour Checklist (CBCL) and the Child Behaviour Questionnaire (CBQ). Across a broad range of measures, we found no significant group differences in attention or activity level at 10 months between infants with and without a family history of ADHD or ASD. However, parent and observer ratings of infant activity level at 10 months were positively associated with later preschool ADHD traits at 3 years. Observable behavioural differences in activity level (but not attention) may be apparent from infancy in children who later develop elevated preschool ADHD traits.

How Does Temperament in Toddlers at Elevated Likelihood for Autism Relate to Symptoms of Autism and ADHD at Three Years of Age?

The current study investigated longitudinal associations between parent-rated temperament, observed exuberance and accelerometer activity level at 18-months and symptoms of ASD and ADHD at 36-months in a sample of 54 children at elevated likelihood for ASD. For the specific parent-rated temperament scales, most observed significant associations appeared to be specific for either ASD or ADHD symptoms. Indeed, by controlling for overlapping symptoms a different pattern of associations emerged. These results illustrate how temperamental measures may signal risk for later ASD versus ADHD symptomatology in infants at elevated likelihood for ASD. In addition, they indicate the potential of adopting a broader view on neurodevelopmental disorders by investigating not only ASD traits, but also co-occurring disorders such as ADHD in samples of elevated likelihood for ASD.

Cortical Gyrification Morphology in Individuals with ASD and ADHD across the Lifespan: A Systematic Review and Meta-Analysis

Autism spectrum disorder (ASD) and attention-deficit hyperactivity disorder (ADHD) are common neurodevelopmental disorders (NDDs) that may impact brain maturation. A number of studies have examined cortical gyrification morphology in both NDDs. Here we review and when possible pool their results to better understand the shared and potentially disorder-specific gyrification features. We searched MEDLINE, PsycINFO, and EMBASE databases, and 24 and 10 studies met the criteria to be included in the systematic review and meta-analysis portions, respectively. Meta-analysis of local Gyrification Index (lGI) findings across ASD studies was conducted with SDM software adapted for surface-based morphometry studies. Meta-regressions were used to explore effects of age, sex, and sample size on gyrification differences. There were no significant differences in gyrification across groups. Qualitative synthesis of remaining ASD studies highlighted heterogeneity in findings. Large-scale ADHD studies reported no differences in gyrification between cases and controls suggesting that, similar to ASD, there is currently no evidence of differences in gyrification morphology compared with controls. Larger, longitudinal studies are needed to further clarify the effects of age, sex, and IQ on cortical gyrification in these NDDs.

Expression analysis of selected genes involved in tryptophan metabolic pathways in Egyptian children with Autism Spectrum Disorder and learning disabilities

Autism Spectrum Disorder (ASD) and learning disabilities are neurodevelopmental disabilities characterized by dramatically increasing incidence rates, yet the exact etiology for these disabilities is not identified. Impairment in tryptophan metabolism has been suggested to participate in the pathogenesis of ASD, however, further validation of its involvement is required. Additionally, its role in learning disabilities is still uninvestigated. Our objective was to evaluate some aspects of tryptophan metabolism in ASD children (N = 45) compared to children with learning disabilities (N = 44) and healthy controls (N = 40) by measuring the expression levels of the MAOA, HAAO and AADAT genes using real-time RT-qPCR. We also aimed to correlate the expression patterns of these genes with parental ages at the time of childbirth, levels of serum iron, and vitamin D3 and zinc/copper ratio, as possible risk factors for ASD. Results demonstrated a significant decrease in the expression of the selected genes within ASD children (p < 0.001) relative to children with learning disabilities and healthy controls, which significantly associated with the levels of our targeted risk factors (p < 0.05) and negatively correlated to ASD scoring (p < 0.001). In conclusion, this study suggests that the expression of the MAOA, HAAO and AADAT genes may underpin the pathophysiology of ASD.

Behavioural and neural markers of tactile sensory processing in infants at elevated likelihood of autism spectrum disorder and/or attention deficit hyperactivity disorder

Backgrounds

Atypicalities in tactile processing are reported in autism spectrum disorder (ASD) and attention deficit hyperactivity disorder (ADHD) but it remains unknown if they precede and associate with the traits of these disorders emerging in childhood. We investigated behavioural and neural markers of tactile sensory processing in infants at elevated likelihood of ASD and/or ADHD compared to infants at typical likelihood of the disorders. Further, we assessed the specificity of associations between infant markers and later ASD or ADHD traits.

Methods

Ninety-one 10-month-old infants participated in the study (n = 44 infants at elevated likelihood of ASD; n = 20 infants at elevated likelihood of ADHD; n = 9 infants at elevated likelihood of ASD and ADHD; n = 18 infants at typical likelihood of the disorders). Behavioural and EEG responses to pairs of tactile stimuli were experimentally recorded and concurrent parental reports of tactile responsiveness were collected. ASD and ADHD traits were measured at 24 months through standardized assessment (ADOS-2) and parental report (ECBQ), respectively.

Results

There was no effect of infants’ likelihood status on behavioural markers of tactile sensory processing. Conversely, increased ASD likelihood associated with reduced neural repetition suppression to tactile input. Reduced neural repetition suppression at 10 months significantly predicted ASD (but not ADHD) traits at 24 months across the entire sample. Elevated tactile sensory seeking at 10 months moderated the relationship between early reduced neural repetition suppression and later ASD traits.

Conclusions

Reduced tactile neural repetition suppression is an early marker of later ASD traits in infants at elevated likelihood of ASD or ADHD, suggesting that a common pathway to later ASD traits exists despite different familial backgrounds. Elevated tactile sensory seeking may act as a protective factor, mitigating the relationship between early tactile neural repetition suppression and later ASD traits.

Latent Structure of Combined Autistic and ADHD Symptoms in Clinical and General Population Samples: A Scoping Review

Background: Many phenotypic studies have estimated the degree of comorbidity between Autism Spectrum Disorder (ASD) and Attention Deficit Hyperactivity Disorder (ADHD), but few have examined the latent, or unobserved, structure of combined ASD and ADHD symptoms. This is an important perquisite toward better understanding the overlap between ASD and ADHD. Methods: We conducted a scoping review of studies that examined the factor or latent class structure of ASD and ADHD symptoms within the same clinical or general population sample. Results: Eight studies met final inclusion criteria. Four factor analysis studies found that ASD and ADHD domains loaded separately and one found that some ASD and ADHD domains loaded together. In the three latent class studies, there were evidence of profiles with high levels of co-occurring ASD and ADHD symptoms. Conclusions: Our scoping review provides some evidence of phenotypic overlap between ASD and ADHD at the latent, or unobserved, level, particularly when using a "person-centered" (latent class analysis) vs. a "variable-centered" (factor analysis) approach.

Atypical Development of Attentional Control Associates with Later Adaptive Functioning, Autism and ADHD Traits

Autism is frequently associated with difficulties with top-down attentional control, which impact on individuals’ mental health and quality of life. The developmental processes involved in these attentional difficulties are not well understood. Using a data-driven approach, 2 samples (N = 294 and 412) of infants at elevated and typical likelihood of autism were grouped according to profiles of parent report of attention at 10, 15 and 25 months. In contrast to the normative profile of increases in attentional control scores between infancy and toddlerhood, a minority (7–9%) showed plateauing attentional control scores between 10 and 25 months. Consistent with pre-registered hypotheses, plateaued growth of attentional control was associated with elevated autism and ADHD traits, and lower adaptive functioning at age 3 years.

Development of ADHD: Etiology, Heterogeneity, and Early Life Course

ADHD represents a powerful entry point for developmental approaches to psychopathology due to its major role in early emergence of major life problems. One key issue concerns the role of early environmental risks in etiology and maintenance in the context of genetic liability. Here, psychosocial aspects of development need more attention. A second key issue is that phenotypic heterogeneity requires better resolution if actionable causal mechanisms are to be effectively identified. Here, the interplay of cognition and emotion in the context of a temperament lens is one helpful way forward. A third key issue is the poorly understood yet somewhat striking bifurcation of developmental course in adolescence, when a subgroup seem to have largely benign outcomes, while a larger group continue on a problematic path. A final integrative question concerns the most effective conceptualization of the disorder in relation to broader dysregulation. Key scientific priorities are noted.

Early Motor Differences in Infants at Elevated Likelihood of Autism Spectrum Disorder and/or Attention Deficit Hyperactivity Disorder

We investigated infant's manual motor behaviour; specifically behaviours crossing the body midline. Infants at elevated likelihood of Autism Spectrum Disorder (ASD) and/or Attention Deficit Hyperactivity Disorder (ADHD) produced fewer manual behaviours that cross the midline compared to infants with a typical likelihood of developing these disorders; however this effect was limited to 10-month-olds and not apparent at age 5 and 14 months. Although, midline crossing did not predict ASD traits, it was related to ADHD traits at 2 years of age. We rule out motor ability and hand dominance as possible explanations for this pattern of behaviour, positing that these results may be a consequence of multisensory integration abilities, and the neurobehavioural shift period, in the first year of life.

Development of ADHD: Etiology, Heterogeneity, and Early Life Course

ADHD represents a powerful entry point for developmental approaches to psychopathology due to its major role in early emergence of major life problems. One key issue concerns the role of early environmental risks in etiology and maintenance in the context of genetic liability. Here, psychosocial aspects of development need more attention. A second key issue is that phenotypic heterogeneity requires better resolution if actionable causal mechanisms are to be effectively identified. Here, the interplay of cognition and emotion in the context of a temperament lens is one helpful way forward. A third key issue is the poorly understood yet somewhat striking bifurcation of developmental course in adolescence, when a subgroup seem to have largely benign outcomes, while a larger group continue on a problematic path. A final integrative question concerns the most effective conceptualization of the disorder in relation to broader dysregulation. Key scientific priorities are noted.

Screen time in 36-month-olds at increased likelihood for ASD and ADHD

We examined the relationship between video-based media viewing (screen time), behavioral outcomes, and language development in 120 36-month-old children with a family history of Autism Spectrum Disorder (ASD) or Attention-Deficit/Hyperactivity Disorder (ADHD) or no family history of either condition. Participants were classified into one of three diagnostic groups: ASD (n = 20), ADHD Concerns (children with elevated ADHD symptoms; n = 14), or Comparison (n = 86). Children in the ADHD Concerns group spent more time viewing screen media than Comparison children. Increased screen time was associated with lower receptive and expressive language scores across groups. Future longitudinal studies are needed to determine the direction of effects and causality.

AVPR1A main effect and OXTR-by-environment interplay in individual differences in depression level

Background

Multiple studies of depression indicated a significant role of gene-by-environment interactions; however, they are mainly limited to the examination of modulating effect of recent stressful life events. Other environmental factors occurring at different stages of ante- and postnatal development may affect the association between multiple genes and depression. The study aimed to analyze the main and haplotype-based effect of serotonergic system and HPA-axis gene polymorphisms on depression and to detect gene-by-environment interaction models explaining individual variance in depression in mentally healthy young adults from Russia.

Methods

Depression score was assessed using Beck Depression Inventory (BDI) in 623 healthy individuals (81% women; 17-25 years) of Caucasian origin (Russians, Tatars, Udmurts) from Russia. The main- and gene-based effects of 12 SNPs in SLC6A4 (5-HTTLPR, rs1042173), HTR2A (rs7322347), OXTR (rs7632287, rs2254298, rs13316193, rs53576, rs2228485, rs237911), AVPR1A (rs3803107, rs1042615), and AVPR1B (rs33911258) genes, and gene-by-environment interactions were tested with linear regression models (PLINK v.1.9) adjusted for multiple comparisons.

Results

We observed ethnicity-specific main effect of the AVPR1A rs3803107 (P = 0.003; P_FDR = 0.047) and gene-based effect of the OXTR gene (Р = 0.005; P_perm = 0.034) on BDI-measured depression, and modifying effect of paternal care on OXTR rs53576 (P = 0.004; P_FDR = 0.012) and birth order on OXTR rs237911 (P = 0.006; P_FDR = 0.018) association with depression level.

Limitations

A hypothesis driven candidate gene approach, which examined a limited number of genetic variants in a moderately large sample, was used.

Conclusions

Our preliminary findings indicate that familial environment may play a permissive role modulating the manifestation of OXTR-based depression variance in mentally healthy subjects.

White matter alterations in autism spectrum disorder and attention-deficit/hyperactivity disorder in relation to sensory profile

Background

Autism spectrum disorder (ASD) and attention-deficit/hyperactivity disorder (ADHD) have high rates of co-occurrence and share atypical behavioral characteristics, including sensory symptoms. The present diffusion tensor imaging (DTI) study was conducted to examine whether and how white matter alterations are observed in adult populations with developmental disorders (DD) and to determine how brain–sensory relationships are either shared between or distinct to ASD and ADHD.

Methods

We collected DTI data from adult population with DD (a primary diagnosis of ASD: n = 105, ADHD: n = 55) as well as age- and sex-matched typically developing (TD) participants (n = 58). Voxel-wise fractional anisotropy (FA), mean diffusivity, axial diffusivity, and radial diffusivity (RD) were analyzed using tract-based spatial statistics. The severities of sensory symptoms were assessed using the Adolescent/Adult Sensory Profile (AASP).

Results

Categorical analyses identified voxel clusters showing significant effects of DD on FA and RD in the posterior portion of the corpus callosum and its extension in the right hemisphere. Furthermore, regression analyses using the AASP scores revealed that slopes in relationships of FA or RD with the degree of sensory symptoms were parallel between the two DDs in large parts of the affected corpus callosum regions. A small but significant cluster did exist showing difference in association between an AASP subscale score and RD across ASD and ADHD.

Limitations

Wide age range of the participants may be oversimplified.

Conclusions

These results indicate that white matter alteration and their relationships to sensory symptoms are largely shared between ASD and ADHD, with localized abnormalities showing significant between-diagnosis differences within DD.

Look duration at the face as a developmental endophenotype: elucidating pathways to autism and ADHD

Identifying developmental endophenotypes on the pathway between genetics and behavior is critical to uncovering the mechanisms underlying neurodevelopmental conditions. In this proof-of-principle study, we explored whether early disruptions in visual attention are a unique or shared candidate endophenotype of autism spectrum disorder (ASD) and attention-deficit/hyperactivity disorder (ADHD). We calculated the duration of the longest look (i.e., peak look) to faces in an array-based eye-tracking task for 335 14-month-old infants with and without first-degree relatives with ASD and/or ADHD. We leveraged parent-report and genotype data available for a proportion of these infants to evaluate the relation of looking behavior to familial (n = 285) and genetic liability (using polygenic scores, n = 185) as well as ASD and ADHD-relevant temperament traits at 2 years of age (shyness and inhibitory control, respectively, n = 272) and ASD and ADHD clinical traits at 6 years of age (n = 94).

Results showed that longer peak looks at the face were associated with elevated polygenic scores for ADHD (β = 0.078, p = .023), but not ASD (β = 0.002, p = .944), and with elevated ADHD traits in mid-childhood (F(1,88) = 6.401, p = .013, $\eta _p^2$=0.068; ASD: F (1,88) = 3.218, p = .076), but not in toddlerhood (ps > 0.2). This pattern of results did not emerge when considering mean peak look duration across face and nonface stimuli. Thus, alterations in attention to faces during spontaneous visual exploration may be more consistent with a developmental endophenotype of ADHD than ASD. Our work shows that dissecting paths to neurodevelopmental conditions requires longitudinal data incorporating polygenic contribution, early neurocognitive function, and clinical phenotypic variation.

Shared and distinct developmental pathways to ASD and ADHD phenotypes among infants at familial risk

Autism spectrum disorder (ASD) and attention-deficit/hyperactivity disorder (ADHD) are believed to share partially overlapping causal mechanisms suggesting that early risk markers may also overlap. Using latent profile analysis (LPA) in a sample of infants enriched for ASD and ADHD, we first examined the number of distinct groups of 3-year-old children, based on ADHD and ASD symptomatology. To investigate early predictors of ASD and ADHD symptom profiles, we next examined differences in trajectories of infant behaviors among the LPA classes spanning general development, negative affect, attention, activity level, impulsivity, and social behavior. Participants included 166 infants at familial risk for ASD (n = 89), ADHD (n = 38), or low-risk for both (n = 39) evaluated at 12, 18, 24, and 36 months of age. A three-class solution was selected reflecting a Typically Developing (TD) class (low symptoms; n = 108), an ADHD class (high ADHD/low ASD symptoms; n = 39), and an ASD class (high ASD/ADHD symptoms; n = 19). Trajectories of infant behaviors were generally suggestive of a gradient pattern of differences, with the greatest impairment within the ASD class followed by the ADHD class. These findings indicate a mixture of overlapping and distinct early markers of preschool ASD- and ADHD-like profiles that can be difficult to disentangle early in life.

Refining Attention-Deficit/Hyperactivity Disorder and Autism Spectrum Disorder Genetic Loci by Integrating Summary Data From Genome-wide Association, Gene Expression, and DNA Methylation Studies

BACKGROUND

Recent genome-wide association studies (GWASs) identified the first genetic loci associated with attention-deficit/hyperactivity disorder (ADHD) and autism spectrum disorder (ASD). The next step is to use these results to increase our understanding of the biological mechanisms involved. Most of the identified variants likely influence gene regulation. The aim of the current study is to shed light on the mechanisms underlying the genetic signals and prioritize genes by integrating GWAS results with gene expression and DNA methylation (DNAm) levels.

METHODS

We applied summary-data-based Mendelian randomization to integrate ADHD and ASD GWAS data with fetal brain expression and methylation quantitative trait loci, given the early onset of these disorders. We also analyzed expression and methylation quantitative trait loci datasets of adult brain and blood, as these provide increased statistical power. We subsequently used summary-data-based Mendelian randomization to investigate if the same variant influences both DNAm and gene expression levels.

RESULTS

We identified multiple gene expression and DNAm levels in fetal brain at chromosomes 1 and 17 that were associated with ADHD and ASD, respectively, through pleiotropy at shared genetic variants. The analyses in brain and blood showed additional associated gene expression and DNAm levels at the same and additional loci, likely because of increased statistical power. Several of the associated genes have not been identified in ADHD and ASD GWASs before.

CONCLUSIONS

Our findings identified the genetic variants associated with ADHD and ASD that likely act through gene regulation. This facilitates prioritization of candidate genes for functional follow-up studies.

Future Directions for Infant Identification and Intervention for Autism Spectrum Disorder from a Transdiagnostic Perspective

By the time they are typically detected, neurodevelopmental disorders like autism spectrum disorder (ASD) are already challenging to treat. Preventive and early intervention strategies in infancy are critical for improving outcomes over the lifespan with significant cost savings. However, the impact of prevention and early intervention efforts is dependent upon our ability to identify infants most appropriate for such interventions. Because there may be significant overlap between prodromal symptoms across neurodevelopmental disorders and child psychopathology more broadly which may wax and wane across development, we contend that the impact of prevention and early intervention efforts will be heightened by identifying early indicators that may overlap across ASD and other commonly co-occurring disorders. This paper summarizes the existing literature on infant symptoms and identification of ASD to demonstrate the ways in which a transdiagnostic perspective could expand the impact of early identification and intervention research and clinical efforts, and to outline suggestions for future empirical research programs addressing current gaps in the identification-to-treatment pipeline. We propose four recommendations for future research that are both grounded in developmental and clinical science and that are scalable for early intervention systems: (1) development of fine-grained, norm-referenced measures of ASD-relevant transdiagnostic behavioral domains; (2) identification of shared and distinct mechanisms influencing the transition from risk to disorder; (3) determination of key cross-cutting treatment strategies (both novel and extracted from existing approaches) effective in targeting specific domains across disorders; and (4) integration of identified measures and treatments into existing service systems.

The association between social emotional development and symptom presentation in autism spectrum disorder

Understanding differences in social-emotional behavior can help identify atypical development. This study examined the differences in social-emotional development in children at increased risk of an autism spectrum disorder (ASD) diagnosis (infant siblings of children diagnosed with the disorder). Parents completed the Brief Infant-Toddler Social-Emotional Assessment (BITSEA) to determine its ability to flag children with later-diagnosed ASD in a high-risk (HR) sibling population. Parents of HR (n = 311) and low-risk (LR; no family history of ASD; n = 127) children completed the BITSEA when their children were 18 months old and all children underwent a diagnostic assessment for ASD at age 3 years. All six subscales of the BITSEA (Problems, Competence, ASD Problems, ASD Competence, Total ASD Score, and Red Flags) distinguished between those in the HR group who were diagnosed with ASD (n = 84) compared to non-ASD-diagnosed children (both HR-N and LR). One subscale (BITSEA Competence) differentiated between the HR children not diagnosed with ASD and the LR group. The results suggest that tracking early social-emotional development may have implications for all HR children, as they are at increased risk of ASD but also other developmental or mental health conditions.

Individual risk and familial liability for suicide attempt and suicide in autism: a population-based study

BACKGROUND

Studies on the individual gender-specific risk and familial co-aggregation of suicidal behaviour in autism spectrum disorder (ASD) are lacking.

METHODS

We conducted a matched case-cohort study applying conditional logistic regression models on 54 168 individuals recorded in 1987-2013 with ASD in Swedish national registers: ASD without ID n = 43 570 (out of which n = 19035, 43.69% with ADHD); ASD + ID n = 10 598 (out of which n = 2894 individuals, 27.31% with ADHD), and 270 840 controls, as well as 347 155 relatives of individuals with ASD and 1 735 775 control relatives.

RESULTS

The risk for suicidal behaviours [reported as odds ratio OR (95% confidence interval CI)] was most increased in the ASD without ID group with comorbid ADHD [suicide attempt 7.25 (6.79-7.73); most severe attempts i.e. requiring inpatient stay 12.37 (11.33-13.52); suicide 13.09 (8.54-20.08)]. The risk was also increased in ASD + ID group [all suicide attempts 2.60 (2.31-2.92); inpatient only 3.45 (2.96-4.02); suicide 2.31 (1.16-4.57)]. Females with ASD without ID had generally higher risk for suicidal behaviours than males, while both genders had highest risk in the case of comorbid ADHD [females, suicide attempts 10.27 (9.27-11.37); inpatient only 13.42 (11.87-15.18); suicide 14.26 (6.03-33.72); males, suicide attempts 5.55 (5.10-6.05); inpatient only 11.33 (9.98-12.86); suicide 12.72 (7.77-20.82)]. Adjustment for psychiatric comorbidity attenuated the risk estimates. In comparison to controls, relatives of individuals with ASD also had an increased risk of suicidal behaviour.

CONCLUSIONS

Clinicians treating patients with ASD should be vigilant for suicidal behaviour and consider treatment of psychiatric comorbidity.