Autism spectrum disorder and attention-deficit/hyperactivity disorder in early childhood: A review of unique and shared characteristics and developmental antecedents

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.

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.

Cross-Disorder Analysis of Brain Structural Abnormalities in Six Major Psychiatric Disorders: A Secondary Analysis of Mega- and Meta-analytical Findings From the ENIGMA Consortium

BACKGROUND

Neuroimaging studies have consistently reported similar brain structural abnormalities across different psychiatric disorders. Yet, the extent and regional distribution of shared morphometric abnormalities between disorders remains unknown.

METHODS

Here, we conducted a cross-disorder analysis of brain structural abnormalities in 6 psychiatric disorders based on effect size estimates for cortical thickness and subcortical volume differences between healthy control subjects and psychiatric patients from 11 mega- and meta-analyses from the ENIGMA (Enhancing Neuro Imaging Genetics Through Meta Analysis) consortium. Correlational and exploratory factor analyses were used to quantify the relative overlap in brain structural effect sizes between disorders and to identify brain regions with disorder-specific abnormalities.

RESULTS

Brain structural abnormalities in major depressive disorder, bipolar disorder, schizophrenia, and obsessive-compulsive disorder were highly correlated (r = .443 to r = .782), and one shared latent underlying factor explained between 42.3% and 88.7% of the brain structural variance of each disorder. The observed shared morphometric signature of these disorders showed little similarity with brain structural patterns related to physiological aging. In contrast, patterns of brain structural abnormalities independent of all other disorders were observed in both attention-deficit/hyperactivity disorder and autism spectrum disorder. Brain regions showing high proportions of independent variance were identified for each disorder to locate disorder-specific morphometric abnormalities.

CONCLUSIONS

Taken together, these results offer novel insights into transdiagnostic as well as disorder-specific brain structural abnormalities across 6 major psychiatric disorders. Limitations comprise the uncertain contribution of risk factors, comorbidities, and medication effects to the observed pattern of results that should be clarified by future research.

Brief Report: Associations Between Cognitive Control Processes and Traits of Autism Spectrum Disorder (ASD), attention-Deficit/Hyperactivity Disorder (ADHD) and Anxiety in Children at Elevated and Typical Familial Likelihood for ASD

Shared difficulties with cognitive control may play a role in co-occurring mental health problems frequently observed in autistic children. We investigated how different cognitive control processes (inhibitory control, conflict resolution, cognitive flexibility) associated with traits of autism spectrum disorder (ASD), attention-deficit/hyperactivity disorder (ADHD) and anxiety in 7-year-old children at elevated (n = 44) and typical (n = 37) familial likelihood for ASD. Poor inhibitory control was associated with higher ADHD traits. Better inhibitory control and poorer cognitive flexibility predicted higher anxiety traits. Cognitive control processes were not associated dimensionally with autistic traits, though better conflict resolution predicted greater likelihood of meeting diagnostic criteria for ASD in categorical analysis. These findings suggest that different cognitive control alterations are associated with ASD, ADHD and anxiety.

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.

Efficacy of a Virtual Reality Biofeedback Game (DEEP) to Reduce Anxiety and Disruptive Classroom Behavior: Single-Case Study

BACKGROUND

Many adolescents in special education are affected by anxiety in addition to their behavioral problems. Anxiety leads to substantial long-term problems and may underlie disruptive behaviors in the classroom as a result of the individual's inability to tolerate anxiety-provoking situations. Thus, interventions in special needs schools that help adolescents cope with anxiety and, in turn, diminish disruptive classroom behaviors are needed.

OBJECTIVE

This study aimed to evaluate the effect of a virtual reality biofeedback game, DEEP, on daily levels of state-anxiety and disruptive classroom behavior in a clinical sample. In addition, the study also aimed to examine the duration of the calm or relaxed state after playing DEEP.

METHODS

A total of 8 adolescents attending a special secondary school for students with behavioral and psychiatric problems participated in a single-case experimental ABAB study. Over a 4-week period, participants completed 6 DEEP sessions. In addition, momentary assessments (ie, 3 times a day) of self-reported state-anxiety and teacher-reported classroom behavior were collected throughout all A and B phases.

RESULTS

From analyzing the individual profiles, it was found that 6 participants showed reductions in anxiety, and 5 participants showed reductions in disruptive classroom behaviors after the introduction of DEEP. On a group level, results showed a small but significant reduction of anxiety (d=-0.29) and a small, nonsignificant reduction of disruptive classroom behavior (d=-0.16) on days when participants played DEEP. Moreover, it was found that the calm or relaxed state of participants after playing DEEP lasted for about 2 hours on average.

CONCLUSIONS

This study demonstrates the potential of the game, DEEP, as an intervention for anxiety and disruptive classroom behavior in a special school setting. Future research is needed to fully optimize and personalize DEEP as an intervention for the heterogeneous special school population.

Polygenic Risk Scores for Developmental Disorders, Neuromotor Functioning During Infancy, and Autistic Traits in Childhood

BACKGROUND

Impaired neuromotor development is often one of the earliest observations in children with autism spectrum disorder (ASD). We investigated whether a genetic predisposition to developmental disorders was associated with nonoptimal neuromotor development during infancy and examined the genetic correlation between nonoptimal neuromotor development and autistic traits in the general population.

METHODS

In a population-based cohort in The Netherlands (2002-2006), we calculated polygenic risk scores (PRSs) for ASD and attention-deficit/hyperactivity disorder (ADHD) using genome-wide association study summary statistics. In 1921 children with genetic data, parents rated autistic traits at 6 years of age. Among them, 1174 children (61.1%) underwent neuromotor examinations (tone, responses, senses, and other observations) during infancy (9-20 weeks of age). We used linear regressions to examine associations of PRSs with neuromotor scores and autistic traits. We performed a bivariate genome-based restricted maximum likelihood analysis to explore whether genetic susceptibility underlies the association between neuromotor development and autistic traits.

RESULTS

Higher PRSs for ASD were associated with less optimal overall infant neuromotor development, in particular low muscle tone. Higher PRSs for ADHD were associated with less optimal senses. PRSs for ASD and those for ADHD both were associated with autistic traits. The single nucleotide polymorphism-based heritability of overall motor development was 20% (SE = .21) and of autistic traits was 68% (SE = .26). The genetic correlation between overall motor development and autistic traits was .35 (SE = .21, p < .001).

CONCLUSIONS

We found that genetic liabilities for ASD and ADHD covary with neuromotor development during infancy. Shared genetic liability might partly explain the association between nonoptimal neuromotor development during infancy and autistic traits in childhood.

Early motor signs of attention-deficit hyperactivity disorder: a systematic review

ADHD is a common neurodevelopmental disorder with onset of symptoms typically in early childhood. First signs of the disorder, including language delay, motor delay and temperament characteristics, may be evident as early as infancy. The present review describes published evidence about early motor signs of either children with later symptoms of ADHD or a later diagnosis of the disorder. Nine published cohort studies were included after a systematic search of related terms in PubMed and PsycInfo databases. Study eligibility criteria included: (1) report on early motor function or any motor-related signs; (2) the presence of a participants' assessment by/at 12 months of age; (3) report of a later presence of ADHD symptoms. The limited number of reports included suggests an association between mild early neurological markers and later developmental coordination disorder and motor overflow movements. Unfortunately, due to their small sample sizes and focus on group reports rather than individuals, they have limited power to find strong associations. Early motor indicators of ADHD, if present, appear to be non-specific, and therefore not yet useful in clinical screening. Spontaneous motility seems to be a promising measure for early ADHD detection, although further studies with large cohorts are recommended to determine its clinical role in children at risk for ADHD.

From Toddlerhood to Adolescence: Which Characteristics Among Toddlers with Autism Spectrum Disorder Predict Adolescent Attention Deficit/Hyperactivity Symptom Severity? A Long-Term Follow-Up Study

High rates of attention deficit/hyperactivity disorder (ADHD) comorbidity have been described in autism spectrum disorder (ASD). This study searched for predictors at toddlerhood of the severity of ADHD symptoms at adolescence. The study included 65 participants, (mean age = 13:8 year), diagnosed with ASD at toddlerhood. Participants underwent a comprehensive assessment of cognitive ability, adaptive skills and autism severity at toddlerhood and adolescence. More severe restricted and repetitive behaviors (RRB) in toddlerhood predicted the severity of Inattention symptoms. In addition, more severe RRB and lower adaptive skills in the toddler years significantly predicted the severity of Hyperactivity/Impulsivity symptoms. Adolescents with elevated ADHD symptoms diagnosed at toddlerhood with ASD showed lower cognitive and adaptive skills and more severe autism symptoms.

Gut microbiota composition is associated with temperament traits in infants

BACKGROUND

One of the key behavioral phenotypes in infancy are different temperament traits, and certain early life temperament traits have been shown to precede later mental health problems. Differences in the gut microbiota composition (GMC) have been suggested to link with neurodevelopment. For example, toddler temperament traits have been found to associate with differences in GMC; however, studies in infants are lacking although infancy is a rapid period of neurodevelopment as well as GM development. Thus, we aimed to investigate association between infant GMC and temperament.

METHODS

The study population (n = 301, 53% boys) was drawn from the FinnBrain Birth Cohort Study. Stool samples were collected from the 2.5-month-old infants and sequenced with 16S Illumina MiSeq platform. GMC taxonomic composition (at Genus and OTU level), observed sample clusters, diversity and richness were investigated in relation to the maternal reports of Infant Behavior Questionnaire -Revised (IBQ-R) at the age of 6 months.

RESULTS

Three sample clusters (Bifidobacterium/Enterobacteriaceae, Bacteroides, V. Dispar) based on GMC were identified, of which Bifidobacterium/Enterobacteriaceae-cluster presented with higher scores on the IBQ-R main dimension regulation and its subscale duration of orienting compared to Bacteroides-cluster. The clusters associated with temperament in a sex-dependent manner. The IBQ-R main dimension surgency (positive emotionality) was associated positively both with genus Bifidobacterium and Streptococcus. Alpha diversity had a negative association with negative emotionality and fear reactivity.

CONCLUSION

This is the first study demonstrating associations, but not causal connections, between GMC and temperament in young infants in a prospective design.

Preterm birth subtypes, placental pathology findings, and risk of neurodevelopmental disabilities during childhood

INTRODUCTION

Preterm birth (PTB) and in-utero inflammation are recognized risk factors of neurodevelopmental disabilities (NDDs); however, their combined role in NDDs is unknown. We examined the independent and joint association of PTB and placental histological findings with the childhood risk of NDDs (overall and by subgroups including autism spectrum disorder (ASD) and ADHD).

METHODS

We analyzed data from the Boston Birth Cohort, where mother-infant pairs were enrolled at birth and followed from birth onwards. Birth outcomes, placental pathology and NDDs were obtained from electronic medical records. Placental pathology was categorized using a standardized classification system proposed by the Amsterdam Placental Workshop Group.

RESULTS

PTB (all, including spontaneous, medically indicated) was an independent risk factor for NDDs. Placental histological chorioamnionitis (CA) and PTB additively increased the odds of NDDs (aOR: 2.16, 95% CI: 1.37, 3.39), as well as ADHD (aOR: 2.75, 95% CI: 1.55, 4.90), other developmental disabilities (aOR: 1.96, 95% CI: 1.18, 3.25) and possibly ASD (aOR: 2.31, 95% CI: 0.99, 5.39). The above associations were more pronounced in spontaneous than medically indicated PTB. PTB alone in the absence of CA only had a moderate association with ASD and ADHD. Placental maternal vascular malperfusion alone or in combination with PTB was not associated with the risk of NDDs.

DISCUSSION

Our study provided new insights on PTB and NDDs by further considering preterm subtypes and placental histology. We revealed that children of spontaneous PTB along with histological CA were at the highest risk for a spectrum of NDDs.

Commentary on… the overlapping and distinct resting functional connectivity between autism spectrum disorder and attention-deficit hyperactivity disorder

Altered neural connectivity in neurodevelopmental disorders is likely subtle, meaning that neuroimaging literature studying development has produced heterogeneous findings. A recent study, published in this issue, illustrates the translational potential of functional connectivity magnetic resonance imaging findings as a biomarker for attention-deficit hyperactivity disorder and autism spectrum disorder. Importantly, it highlights the overlap between disorders, emphasising the need for transdiagnostic and dimensional approaches in neurodevelopment.Declaration of interestNone.

Infant Social Avoidance Predicts Autism but Not Anxiety in Fragile X Syndrome

Objective: Autism spectrum disorder (ASD), attention-deficit/hyperactivity disorder (ADHD), and anxiety are three of the most common childhood psychiatric disorders. Early trajectories of social avoidance have been linked with these psychiatric disorders in previous studies, but it remains unclear how social avoidance differentially predicts comorbid disorders in a high-risk genetic subgroup. Here, we delineate the association between trajectories of social avoidance from infancy and subsequent ASD, ADHD, and anxiety outcomes at preschool in children with fragile X syndrome (FXS), a well-characterized single-gene disorder highly associated with social avoidance as well as elevated rates of ASD, ADHD, and anxiety. Method: Males with FXS (n = 78) aged 4-62 months participated in a longitudinal study resulting in 201 assessments. The Social Avoidance Scale (SAS) documented socially avoidant behaviors from infancy in three domains-physical movement, facial expression, and eye contact during both the first minute and the last hour of an interaction. ASD, ADHD, and anxiety symptom outcomes at preschool were measured via parent-report questionnaires. Results: Increased social avoidance across infancy and preschool predicted elevated ASD symptom severity but reduced ADHD and anxiety symptom severity in males with FXS. Conclusion: ASD, ADHD, and anxiety symptoms relate inconsistently to social avoidance behaviors, providing new insight toward the debate of independence or overlap among these disorders in FXS and other disorders (i.e., ASD). The results suggest that the nuanced profile of the developmental and temporal aspects of social avoidance may inform more the accuracy of differential diagnoses of comorbid psychiatric disorders in FXS.

Dissociation of impulsivity and aggression in mice deficient for the ADHD risk gene Adgrl3: Evidence for dopamine transporter dysregulation

Adhesion G protein-coupled receptor L3 (ADGRL3, LPHN3) has putative roles in neuronal migration and synapse function. Various polymorphisms in ADGRL3 have been linked with an increased risk of attention deficit/hyperactivity disorder (ADHD). In this study, we examined the characteristics of Adgrl3-deficient mice in multiple behavioural domains related to ADHD: locomotive activity, impulsivity, gait, visuospatial and recognition memory, sociability, anxiety-like behaviour and aggression. Additionally, we investigated the effect of Adgrl3-depletion at the transcriptomic level by RNA-sequencing three ADHD-relevant brain regions: prefrontal cortex (PFC), hippocampus and striatum. Adgrl3^-/- mice show increased locomotive activity across all tests and subtle gait abnormalities. These mice also show impairments across spatial memory and learning domains, alongside increased levels of impulsivity and sociability with decreased aggression. However, these alterations were absent in Adgrl3^+/- mice. Across all brain regions tested, the numbers of genes found to exhibit differential expression was relatively small, indicating a specific pathway of action, rather than a broad neurobiological perturbation. Gene-set analysis of differential expression in the PFC detected a number of ADHD-relevant pathways including dopaminergic synapses as well as cocaine and amphetamine addiction. The Slc6a3 gene coding for the dopamine transporter was the most dysregulated gene in the PFC. Unexpectedly, several neurohormone/peptides which are typically only expressed in the hypothamalus were found to be dysregulated in the striatum. Our study further validates Adgrl3 constitutive knockout mice as an experimental model of ADHD while providing neuroanatomical targets for future studies involving ADGRL3 modified models. This article is part of the Special Issue entitled 'Current status of the neurobiology of aggression and impulsivity'.

Social functioning in youth with attention-deficit/hyperactivity disorder and autism spectrum disorder: transdiagnostic commonalities and differences

Attention-Deficit/Hyperactivity Disorder (ADHD) and Autism Spectrum Disorder (ASD) are both neurodevelopmental disorders originating in childhood with high associated impairments and public health significance. There has been growing recognition of the frequent co-occurrence, and potential interrelatedness, between ADHD and ASD without intellectual disability. In fact, the most recent (5th) edition of the DSM is the first to allow ADHD and ASD to be diagnosed in the same individual. The study of transdiagnostic features in ADHD and ASD is important for understanding, and treating, these commonly co-occurring disorders. Social impairment is central to the description and prognosis of both disorders, and many youth with some combination of ADHD and ASD present to clinics for social skills training interventions. However, the aspects of social functioning that are impaired may have both shared and distinct features between the two disorders, relating to some overlapping and some diverse etiologies of social problems in ADHD compared to ASD. These findings have implications for interventions to address social problems in youth with these conditions. We conclude with a discussion about areas for future research and novel intervention targets in youth with ADHD, ASD, and their comorbidity.

Neurodevelopmental Disorders and Adaptive Functions: A Study of Children With Autism Spectrum Disorders (ASD) and/or Attention Deficit and Hyperactivity Disorder (ADHD)

Introduction: Autism spectrum disorder (ASD) and attention deficit and hyperactivity disorder (ADHD) are the two most common neurodevelopmental disorders observed in childhood. The DSM-5 accepts a combined diagnosis of ADHD and ASD, while the DSM-IV did not. The aim of this study was to identify and evaluate the adaptive profile of children and adolescents with a diagnosis of comorbid ADHD and ASD, in comparison with adaptive functioning in subjects with a diagnosis of only ASD or ADHD. Materials and Methods: Ninety-one children (77 boys, 14 girls), aging from 3.1 to 13.4 years (mean age: 8.3 ± 7.2), who met the criteria for a diagnosis of ASD and/or ADHD were enrolled. A neuropsychological evaluation involving cognitive and adaptive assessment was conducted using the Autism Diagnostic Observation Schedule - Second Edition (ADOS-2), the Conners' Parent Rating Scale - Revised: Long Version (CPRS-R), the Wechsler Intelligence Scale - Fourth Edition or the Griffiths Mental Developmental Scales - Extended Revised, the Vineland Adaptive Behaviour Scale - Second Edition (VABS-II). Conclusion: As to the adaptive skills in the three groups evaluated, a worse general profile was ascertained in the ASD and in ASD plus ADHD groups in comparison with respect to the ADHD-only group. With VABS-II evaluation, we found significant differences among the three groups across all domains and combined scores: Communication (F = 18.960; p < 0.001), Socialization (F = 25.410; p < 0.001), Daily Living Skills (F = 19.760; p < 0.001), Motor (F = 9.615; p < 0.001), and Adaptive behavior composite [ABC] (F = 29.370; p < 0.001). Implications of neurodevelopmental double diagnosis such as ASD plus ADHD are discussed.

Twenty years of research on attention-deficit/hyperactivity disorder (ADHD): looking back, looking forward

In this clinical review we summarise what in our view have been some the most important advances in the past two decades, in terms of diagnostic definition, epidemiology, genetics and environmental causes, neuroimaging/cognition and treatment of attention-deficit/hyperactivity disorder (ADHD), including: (1) the most recent changes to the diagnostic criteria in the Diagnostic and Statistical Manual of Mental Disorders and International Classification of Diseases; (2) meta-analytic evidence showing that, after accounting for diagnostic methods, the rates of ADHD are fairly consistent across Western countries; (3) the recent finding of the first genome-wide significant risk loci for ADHD; (4) the paradigm shift in the pathophysiological conceptualisation of ADHD from alterations in individual brain regions to a complex dysfunction in brain networks; (5) evidence supporting the short-term efficacy of ADHD pharmacological treatments, with a different profile of efficacy and tolerability in children/adolescents versus adults; (6) a series of meta-analyses showing that, while non-pharmacological treatment may not be effective to target ADHD core symptoms, some of them effectively address ADHD-related impairments (such as oppositional behaviours for parent training and working memory deficits for cognitive training). We also discuss key priorities for future research in each of these areas of investigation. Overall, while many research questions have been answered, many others need to be addressed. Strengthening multidisciplinary collaborations, relying on large data sets in the spirit of Open Science and supporting research in less advantaged countries will be key to face the challenges ahead.

Head circumference at birth and childhood developmental disorders in a nationwide cohort in Denmark

BACKGROUND

Early markers of Attention Deficit Hyperactivity Disorder (ADHD) and Autism Spectrum Disorder (ASD) may improve the understanding and early recognition of these disorders. We aimed to estimate the association between head circumference at birth, a measure of cerebral size at birth, and the risk of ADHD and ASD.

METHODS

We present a register-based cohort study of all Danish singletons born alive between 1997 and 2013. Cox proportional hazards regression was used for the statistical analyses. Sibling-matched analyses were performed to account for unmeasured confounding shared by siblings.

RESULTS

The analyses included 986 909 new-borns. Compared to normocephalic children, microcephaly was associated with an increased risk of ADHD (hazard ratio [HR] 1.22, 95% confidence interval [CI] 1.12, 1.32). Macrocephaly was associated with a decreased risk of ADHD (HR 0.90, 95% CI 0.82, 0.99). Neither microcephaly nor macrocephaly were associated with ASD (HR 1.06, 95% CI 0.94, 1.19 and 1.03, 95% CI 0.90, 1.19). The largest difference was found within the normocephalic children. A head circumference at the lower limit of normocephaly compared to a head circumference at the upper limit was associated with an increased risk of ADHD (HR 1.52, 95% CI 1.43, 1.63). The sibling analyses confirmed the increased risk of ADHD with decreasing head circumference in the normocephalic children. No other clear associations were present in the sibling analyses.

CONCLUSIONS

Within normocephalic children, smaller head circumference at birth was associated with a higher risk of ADHD. Restricted foetal brain growth may be a risk factor for the development of ADHD but not ASD.

Overactivity, impulsivity and repetitive behaviour in males with fragile X syndrome: contrasting developmental trajectories in those with and without elevated autism symptoms

BACKGROUND

Hyperactivity and repetitive behaviour are characteristic features of fragile X syndrome (FXS). However, little is known about the influence of autism symptomatology on how these characteristics develop over time. We investigate the profiles and developmental trajectories of overactivity, impulsivity and repetitive behaviour, in males with FXS over three time points spanning 8 years.

METHOD

Participants formed two subgroups, those who displayed elevated symptoms of autism at Time 1 (n = 37; M_age  = 16.32; age range = 6.61-43.51) and those who did not (n = 32; M_age  = 8.43; age range = 8.94-47.49).

RESULTS

Participants without elevated symptoms of autism showed a reduction in impulsivity and repetitive questioning over time, whereas those with elevated symptoms of autism did not. Differences between the two subgroups in several topographies of repetitive behaviour emerged at Time 3 only.

CONCLUSIONS

These results further understanding of the relationship between autistic phenomenology and behavioural characteristics in FXS.

The role of epigenetic modifications in neurodevelopmental disorders: A systematic review

Epigenetic processes have been suggested as key mechanisms in the etiology of neurodevelopmental disorders. This systematic review summarizes the current evidence for an association between epigenetics and Autism Spectrum Disorder (ASD) and Attention/Deficit-Hyperactivity Disorder (ADHD). Six databases were searched until the 24th of October 2017. Of the 2169 retrieved articles, 29 met our inclusion criteria. While generally associations between epigenetics and neurodevelopmental disorders were reported, only a few findings were consistent across independent analyses. Differential epigenetic markers were repeatedly identified in OR2L13, C11orf21/TSPAN32, PRRT1 and H3K27 for autism, and in VIPR2 for ADHD. Overall, evidence of an association between epigenetic modifications and ASD or ADHD should be considered preliminary and based on studies suffering from numerous caveats. We highlight the need for carefully designed investigations and for greater homogeneity and provide specific recommendations for future research. Despite the current limited understanding, the suggestive findings and rapid advances in the field hold the promise of a forthcoming elucidation of the role of epigenetic modifications in neurodevelopmental disorders.

Psychophysiological and Behavioral Responses to a Novel Intruder Threat Task for Children on the Autism Spectrum

We measured skin conductance response (SCR) to escalating levels of a direct social threat from a novel, ecologically-relevant experimental paradigm, the Intruder Threat Task. We simultaneously evaluated the contribution of social symptom severity and behavioral movement. Children with AS group showed less psychophysiological reactivity to social threat than controls across all three phases of the experiment. In the AS group, greater social impairment was significantly associated with reduced SCR. However, movement activity predicted SCR while diagnosis did not. Research and treatment need to account for the complex interplay of emotional reactivity and social behavior in AS. Psychophysiology studies of AS should consider the impact of possible confounds such as movement.

Attention deficit hyperactivity disorder and autism spectrum disorder symptoms in school-age children born very preterm

BACKGROUND

Very preterm (VP) children face a broad range of neurodevelopmental sequelae, including behavioral problems.

AIM

To investigate prevalence, pervasiveness and co-occurrence of symptoms of attention deficit hyperactivity disorder (ADHD) and autism spectrum disorder (ASD) in school-age children born very preterm.

METHODS

Using questionnaire and diagnostic interview data, parent and teacher reported symptoms of ADHD and ASD of 57 VP-children (mean age = 9.2 years) were compared with 57 gender and age matched full-term children using t-tests. Intra-class correlation coefficients quantified parent-teacher agreement. Correlation analysis investigated co-occurrence of ADHD/ASD symptoms. ADHD/ASD measures were aggregated using principal component analysis. Regression analyses investigated the contribution of perinatal risk factors, sex and SES to ADHD/ASD symptoms.

RESULTS

VP-children showed higher levels of parent and teacher reported attention problems, social impairment and compromised communication skills. Fair to strong agreement was found between parent and teacher reported ADHD and ASD symptoms, indicating pervasiveness of observed difficulties. Co-occurrence of ADHD and ASD symptoms in VP-children was found. Lower gestational age was associated with higher ADHD and ASD symptom levels, male sex with higher ADHD symptom levels and lower SES with higher ASD symptom levels.

CONCLUSION

School-age VP-children show higher levels of ADHD and ASD symptoms, and attention, socialization and communication difficulties in particular. Routinely screening for these problems is recommended in follow-up care.

Developmental change in look durations predicts later effortful control in toddlers at familial risk for ASD

BACKGROUND

Difficulties with executive functioning (EF) are common in individuals with a range of developmental disorders, including autism spectrum disorder (ASD). Interventions that target underlying mechanisms of EF early in development could be broadly beneficial, but require infant markers of such mechanisms in order to be feasible. Prospective studies of infants at high familial risk (HR) for ASD have revealed a surprising tendency for HR toddlers to show longer epochs of attention to faces than low-risk (LR) controls. In typical development, decreases in look durations towards the end of the first year of life are driven by the development of executive attention-a foundational component of EF. Here, we test the hypothesis that prolonged attention to visual stimuli (including faces) in HR toddlers reflects early differences in the development of executive attention.

METHODS

In a longitudinal prospective study, we used eye-tracking to record HR and LR infants' looking behaviour to social and non-social visual stimuli at ages 9 and 15 months. At age 3 years, we assessed children with a battery of clinical research measures and collected parental report of effortful control (EC)-a temperament trait closely associated with EF and similarly contingent on executive attention.

RESULTS

Consistent with previous studies, we found an attenuated reduction in peak look durations to faces between 9 and 15 months for the HR group compared with the LR group, and lower EC amongst the HR-ASD group. In line with our hypothesis, change in peak look duration to faces between 9 and 15 months was negatively associated with EC at age 3.

CONCLUSIONS

We suggest that for HR toddlers, disruption to the early development of executive attention results in an attenuated reduction in looking time to faces. Effects may be more apparent for faces due to early biases to orient towards them; further, attention difficulties may interact with earlier emerging differences in social information processing. Our finding that prolonged attention to faces may be an early indicator of disruption to the executive attention system is of potential value in screening for infants at risk for later EF difficulties and for evaluation of intervention outcomes.

A Causal and Mediation Analysis of the Comorbidity Between Attention Deficit Hyperactivity Disorder (ADHD) and Autism Spectrum Disorder (ASD)

Autism spectrum disorder (ASD) and Attention-deficit/hyperactivity disorder (ADHD) are often comorbid. The purpose of this study is to explore the relationships between ASD and ADHD symptoms by applying causal modeling. We used a large phenotypic data set of 417 children with ASD and/or ADHD, 562 affected and unaffected siblings, and 414 controls, to infer a structural equation model using a causal discovery algorithm. Three distinct pathways between ASD and ADHD were identified: (1) from impulsivity to difficulties with understanding social information, (2) from hyperactivity to stereotypic, repetitive behavior, (3) a pairwise pathway between inattention, difficulties with understanding social information, and verbal IQ. These findings may inform future studies on understanding the pathophysiological mechanisms behind the overlap between ASD and ADHD.

Severity of Autism Symptoms and Degree of Attentional Difficulties Predicts Emotional and Behavioral Problems in Children with High-Functioning Autism; a Two-Year Follow-up Study

Children with autism often struggle with emotional and behavioral problems (EBP). This study investigated whether level of autism symptoms, attention problems or verbal IQ at baseline can predict EBP 2 years later in children with High-Functioning Autism (HFA). Thirty-four participants with HFA and 45 typically developing children (TD) (ages 9-16) were assessed with parent ratings of EBP, autism symptoms, attention problems, and a test of verbal IQ. The amount of autism symptoms and degree of attention problems at baseline significantly predicted EBP at follow-up, whereas verbal IQ did not. The findings from this study emphasize the importance of assessing and understanding the consequences of autism symptoms and attention problems when treating EBP in children with HFA. Furthermore, interventions aimed at improving ASD symptoms may positively affect the prevalence of EBP in children with HFA.

The Occupational Transition Process to Upper Secondary School, Further Education and/or Work in Sweden: As Described by Young Adults with Asperger Syndrome and Attention Deficit Hyperactivity Disorder

The aim was to describe the occupational transition process to upper secondary school, further education and/or work, and to discover what support influences the process from the perspectives of young adults with Asperger syndrome or attention deficit/hyperactivity disorder. This qualitative study was performed in Sweden and comprised interviews with 15 young adults recruited from community based day centres. Support influencing the process included: occupational transition preparation in compulsory school, practical work experience in a safe environment, and support beyond the workplace. The overall understanding shows that the occupational transition process was a longitudinal one starting as early as in middle school, and continuing until the young adults obtained and were able to remain in employment or further education.

A review of prevalence studies of Autism Spectrum Disorder by latitude and solar irradiance impact

Autism Spectrum Disorder (ASD) is a lifelong disability with no known cause or cure. Among the suggested etiologies, is Cannell's hypothesis of a deficiency in Vitamin D the main natural source of which is Solar Ultraviolet-B (UVB) radiation. The aim in this paper is to build on this hypothesis and explore the relationship of solar irradiance of which UVB is a component, by latitude with the prevalence rates of ASD. Twenty-five reports published between 2011 and 2016 using comparable diagnostic criteria were reviewed. The results suggest a tendency for the prevalence rates of ASD to be lowest in countries near the equator and for this rate to increase as the latitude increases. These findings provide some support not just for the Vitamin D hypothesis, but also for a new proposition that along with UVB radiation, the entire solar radiation spectrum which reaches the earth, may play a role in ASD. While these results are both novel and encouraging in terms of the potential efficacy of exposure to natural sunlight, further research is warranted before results can be considered definitive, and before the implications of the findings can be implemented clinically.

Variation in the Early Trajectories of Autism Symptoms Is Related to the Development of Language, Cognition, and Behavior Problems

OBJECTIVE

The objectives of this study were to model more homogeneous subgroups within autism spectrum disorder (ASD) based on early trajectories of core symptoms; and to further characterize these subgroups in terms of trajectories of language, cognition, co-occurring (attention-deficit/hyperactivity disorder [ADHD]-related) traits and clinical outcome diagnosis.

METHOD

Children (N = 203) referred for possible ASD at ages 1 to 4 years were assessed at three time points at intervals ranging from 9 months to 3 years. Assessments included standardized measures for ASD (Autism Diagnostic Observation Schedule [ADOS]), language (ADOS-language item), nonverbal IQ (NV-IQ; different tests adequate to chronological/mental age), and parent-reported behavioral problems (Infant-Toddler Social and Emotional Assessment, Child Behavior Checklist).

RESULTS

Latent-class growth curve analysis with ADOS total scores led to the identification of three main stable and two small improving groups: a severe-stable group (19.5% of sample)-the only group without considerable language improvement-showed persistent low NV-IQ and marked increase in attention problems over time; a moderate-stable group (21.7%) with below-average increasing NV-IQ; and a mild-stable group (48%) with stable-average NV-IQ and the highest scores on ADHD-related traits, whose ASD outcome diagnoses increased despite stable-low ASD scores. Two groups (each 5.4%) improved: one moved from severe to moderate ASD scores, and the other moved from moderate to mild/nonspectrum scores. Both of these groups improved on language, NV-IQ, and ADHD-related traits.

CONCLUSION

Results support the high stability of ASD symptoms into various severity levels, but also highlight the significant contribution of non-ASD domains in defining and explaining the different ASD trajectories.

Inattention and hyperactivity in association with autism spectrum disorders in the CHARGE study

BACKGROUND

Attention deficits in young children with autism spectrum disorder (ASD) are not well understood. This study sought to determine: 1) the prevalence of ADHD symptoms in young children with ASD, typical development (TD), and developmental delay (DD) and 2) the association between ADHD symptoms and cognitive and behavioral functioning in children with ASD.

METHOD

ADHD symptoms, defined according to Aberrant Behavior Checklist (ABC) hyperactivity subscale scores, were compared across children aged 2-5 from a large case-control study with ASD (n=548), TD (n=423), and DD (n=180). Inattention and hyperactivity items within this subscale were also explored. Within the ASD group, linear and logistic regression were used to examine how ADHD symptoms were associated with cognition as assessed by the Mullen Scales of Early Learning and adaptive functioning as assessed by the Vineland Adaptive Behavior Scales.

RESULTS

Mean hyperactivity subscale scores were lowest in children with TD (mean=3.19), higher in children with DD (12.3), and highest in children with ASD (18.2; between-group p<0.001). Among children with ASD, significant associations were observed with higher ADHD symptoms and poorer adaptive and cognitive functioning (adjusted beta for hyperactivity score in association with: Vineland composite = -5.63, p=0.0005; Mullen visual reception scale = -2.94, p=0.02; for the highest vs. lowest quartile of hyperactivity score, odds of lowest quintile of these scores was approximately doubled). Exploratory analyses highlighted associations with inattention-related items specifically.

CONCLUSION

These results suggest ADHD symptoms may play a key role in the functioning of young children with ASD.

Alterations of Growth Factors in Autism and Attention-Deficit/Hyperactivity Disorder

Growth factors (GFs) are cytokines that regulate the neural development. Recent evidence indicates that alterations in the expression level of GFs during embryogenesis are linked to the pathophysiology and clinical manifestations of attention-deficit/hyperactivity disorder (ADHD) and autism spectrum disorders (ASD). In this concise review, we summarize the current evidence that supports the role of brain-derived neurotrophic factor, insulin-like growth factor 2, hepatocyte growth factor (HGF), glial-derived neurotrophic factor, nerve growth factor, neurotrophins 3 and 4, and epidermal growth factor in the pathogenesis of ADHD and ASD. We also highlight the potential use of these GFs as clinical markers for diagnosis and prognosis of these neurodevelopmental disorders.

Structural brain imaging correlates of ASD and ADHD across the lifespan: a hypothesis-generating review on developmental ASD-ADHD subtypes

We hypothesize that it is plausible that biologically distinct developmental ASD-ADHD subtypes are present, each characterized by a distinct time of onset of symptoms, progression and combination of symptoms. The aim of the present narrative review was to explore if structural brain imaging studies may shed light on key brain areas that are linked to both ASD and ADHD symptoms and undergo significant changes during development. These findings may possibly pinpoint to brain mechanisms underlying differential developmental ASD-ADHD subtypes. To this end we brought together the literature on ASD and ADHD structural brain imaging symptoms and particularly highlight the adolescent years and beyond. Findings indicate that the vast majority of existing MRI studies has been cross-sectional and conducted in children, and sometimes did include adolescents as well, but without explicitly documenting on this age group. MRI studies documenting on age effects in adults with ASD and/or ADHD are rare, and if age is taken into account, only linear effects are examined. Data from various studies suggest that a crucial distinctive feature underlying different developmental ASD-ADHD subtypes may be the differential developmental thinning patterns of the anterior cingulate cortex and related connections towards other prefrontal regions. These regions are crucial for the development of cognitive/effortful control and socio-emotional functioning, with impairments in these features as key to both ASD and ADHD.

Changing ASD-ADHD symptom co-occurrence across the lifespan with adolescence as crucial time window: Illustrating the need to go beyond childhood

Literature on the co-occurrence between Autism Spectrum Disorder (ASD) and Attention-Deficit/Hyperactivity Disorder (ADHD) is strongly biased by a focus on childhood age. A review of the adolescent and adult literature was made on core and related symptoms of ADHD and ASD. In addition, an empirical approach was used including 17,173 ASD-ADHD symptom ratings from participants aged 0 to 84 years. Results indicate that ASD/ADHD constellations peak during adolescence and are lower in early childhood and old age. We hypothesize that on the border of the expected transition to independent adulthood, ASD and ADHD co-occur most because social adaptation and EF skills matter most. Lower correlations in childhood and older age may be due to more diffuse symptoms reflecting respectively still differentiating and de-differentiating EF functions. We plea for a strong research focus in adolescence which may -after early childhood- be a second crucial time window for catching-up pattern explaining more optimal outcomes. We discuss obstacles and oppportunities of a full lifespan approach into old age.