Examining and interpreting the female protective effect against autistic behavior

Umbilical cord blood androgen levels and ASD-related phenotypes at 12 and 36 months in an enriched risk cohort study

Background

Autism spectrum disorder (ASD) affects more than 1% of children in the USA. The male-to-female prevalence ratio of roughly 4:1 in ASD is a well-recognized but poorly understood phenomenon. An explicit focus on potential etiologic pathways consistent with this sex difference, such as those involving prenatal androgen exposure, may help elucidate causes of ASD. Furthermore, the multi-threshold liability model suggests that the genetic mechanisms in females with ASD may be distinct and may modulate ASD risk in families with female ASD in the pedigree.

Methods

We examined umbilical cord blood from 137 children in the Early Autism Risk Longitudinal Investigation (EARLI) cohort. EARLI is an ASD-enriched risk cohort with all children having an older sibling already diagnosed with ASD. Fetal testosterone (T), androstenedione (A4), and dehyroepiandrosterone (DHEA) levels were measured in cord blood using liquid chromatography-tandem mass spectrometry (LC-MS/MS). Robust linear regression models were used to determine associations between cord blood androgen levels and 12-month Autism Observation Scales for Infants (AOSI) scores and 36-month Social Responsiveness Scale (SRS) scores adjusting for potential confounders.

Results

Increasing androgens were not associated with increasing 12-month AOSI score or 36-month total SRS score in either boys or girls. However, the association between T and autistic traits among subjects with a female older affected sibling was greater at 12 months (test of interaction, P = 0.008) and deficits in reciprocal social behavior at 36 months were also greater (test of interaction, P = 0.006) than in subjects whose older affected sibling was male.

Conclusions

While increased prenatal testosterone levels were not associated with autistic traits at 12 or 36 months, our findings of a positive association in infants whose older ASD-affected siblings were female suggests an androgen-related mechanism that may be dependent on, or related to, genetic liability factors present more often in families containing female ASD cases. However, this initial finding, based on a small subgroup of our sample, should be interpreted with considerable caution.

Electronic supplementary material

The online version of this article (doi:10.1186/s13229-017-0118-z) contains supplementary material, which is available to authorized users.

Parent-Endorsed Sex Differences in Toddlers with and Without ASD: Utilizing the M-CHAT

Sex differences in typical development can provide context for understanding ASD. Baron-Cohen (Trends Cogn Sci 6(6):248-254, 2002) suggested ASD could be considered an extreme expression of normal male, compared to female, phenotypic profiles. In this paper, sex-specific M-CHAT scores from N = 53,728 18-month-old toddlers, including n = 185 (32 females) with ASD, were examined. Results suggest a nuanced view of the "extreme male brain theory of autism". At an item level, almost every male versus female disadvantage in the broader population was consistent with M-CHAT vulnerabilities in ASD. However, controlling for total M-CHAT failures, this male disadvantage was more equivocal and many classically ASD-associated features were found more common in non-ASD. Within ASD, females showed relative strengths in joint attention, but impairments in imitation.

Factors influencing the probability of a diagnosis of autism spectrum disorder in girls versus boys

In order to shed more light on why referred girls are less likely to be diagnosed with autism spectrum disorder than boys, this study examined whether behavioral characteristics influence the probability of an autism spectrum disorder diagnosis differently in girls versus boys derived from a multicenter sample of consecutively referred children aged 2.5-10 years. Based on information from the short version of the Developmental, Dimensional and Diagnostic Interview and the Autism Diagnostic Observation Schedule, 130 children (106 boys and 24 girls) received a diagnosis of autism spectrum disorder according to Diagnostic and Statistical Manual of Mental Disorders (4th ed., text rev.) criteria and 101 children (61 boys and 40 girls) did not. Higher overall levels of parent-reported repetitive and restricted behavior symptoms were less predictive of an autism spectrum disorder diagnosis in girls than in boys (odds ratio interaction = 0.41, 95% confidence interval = 0.18-0.92, p = 0.03). In contrast, higher overall levels of parent-reported emotional and behavioral problems increased the probability of an autism spectrum disorder diagnosis more in girls than in boys (odds ratio interaction = 2.44, 95% confidence interval = 1.13-5.29, p = 0.02). No differences were found between girls and boys in the prediction of an autism spectrum disorder diagnosis by overall autistic impairment, sensory symptoms, and cognitive functioning. These findings provide insight into possible explanations for the assumed underidentification of autism spectrum disorder in girls in the clinic.

The role of sex-differential biology in risk for autism spectrum disorder

Autism spectrum disorder (ASD) is a developmental condition that affects approximately four times as many males as females, a strong sex bias that has not yet been fully explained. Understanding the causes of this biased prevalence may highlight novel avenues for treatment development that could benefit patients with diverse genetic backgrounds, and the expertise of sex differences researchers will be invaluable in this endeavor. In this review, I aim to assess current evidence pertaining to the sex difference in ASD prevalence and to identify outstanding questions and remaining gaps in our understanding of how males come to be more frequently affected and/or diagnosed with ASD. Though males consistently outnumber females in ASD prevalence studies, prevalence estimates generated using different approaches report male/female ratios of variable magnitude that suggest that ascertainment or diagnostic biases may contribute to the male skew in ASD. Here, I present the different methods applied and implications of their findings. Additionally, even as prevalence estimations challenge the degree of male bias in ASD, support is growing for the long-proposed female protective effect model of ASD risk, and I review the relevant results from recurrence rate, quantitative trait, and genetic analyses. Lastly, I describe work investigating several sex-differential biological factors and pathways that may be responsible for females' protection and/or males' increased risk predicted by the female protective effect model, including sex steroid hormone exposure and regulation and sex-differential activity of certain neural cell types. However, much future work from both the ASD and sex differences research communities will be required to flesh out our understanding of how these factors act to influence the developing brain and modulate ASD risk.

Current Perspectives in Autism Spectrum Disorder: From Genes to Therapy

Autism spectrum disorder (ASD) is a constellation of neurodevelopmental presentations with high heritability and both phenotypic and genetic heterogeneity. To date, mutations in hundreds of genes have been associated to varying degrees with increased ASD risk. A better understanding of the functions of these genes and whether they fit together in functional groups or impact similar neuronal circuits is needed to develop rational treatment strategies. We will review current areas of emphasis in ASD research, starting from human genetics and exploring how mouse models of human mutations have helped identify specific molecular pathways (protein synthesis and degradation, chromatin remodeling, intracellular signaling), which are linked to alterations in circuit function and cognitive/social behavior. We will conclude by discussing how we can leverage the findings on molecular and cellular alterations found in ASD to develop therapies for neurodevelopmental disorders.

Pleiotropic Mechanisms Indicated for Sex Differences in Autism

Sexual dimorphism in common disease is pervasive, including a dramatic male preponderance in autism spectrum disorders (ASDs). Potential genetic explanations include a liability threshold model requiring increased polymorphism risk in females, sex-limited X-chromosome contribution, gene-environment interaction driven by differences in hormonal milieu, risk influenced by genes sex-differentially expressed in early brain development, or contribution from general mechanisms of sexual dimorphism shared with secondary sex characteristics. Utilizing a large single nucleotide polymorphism (SNP) dataset, we identify distinct sex-specific genome-wide significant loci. We investigate genetic hypotheses and find no evidence for increased genetic risk load in females, but evidence for sex heterogeneity on the X chromosome, and contribution of sex-heterogeneous SNPs for anthropometric traits to ASD risk. Thus, our results support pleiotropy between secondary sex characteristic determination and ASDs, providing a biological basis for sex differences in ASDs and implicating non brain-limited mechanisms.

Hyperactivity and male-specific sleep deficits in the 16p11.2 deletion mouse model of autism

Sleep disturbances and hyperactivity are prevalent in several neurodevelopmental disorders, including autism spectrum disorders (ASDs) and attention deficit-hyperactivity disorder (ADHD). Evidence from genome-wide association studies indicates that chromosomal copy number variations (CNVs) are associated with increased prevalence of these neurodevelopmental disorders. In particular, CNVs in chromosomal region 16p11.2 profoundly increase the risk for ASD and ADHD, disorders that are more common in males than females. We hypothesized that mice hemizygous for the 16p11.2 deletion (16p11.2 del/+) would exhibit sex-specific sleep and activity alterations. To test this hypothesis, we recorded activity patterns using infrared beam breaks in the home-cage of adult male and female 16p11.2 del/+ and wildtype (WT) littermates. In comparison to controls, we found that both male and female 16p11.2 del/+ mice exhibited robust home-cage hyperactivity. In additional experiments, sleep was assessed by polysomnography over a 24-hr period. 16p11.2 del/+ male, but not female mice, exhibited significantly more time awake and significantly less time in non-rapid-eye-movement (NREM) sleep during the 24-hr period than wildtype littermates. Analysis of bouts of sleep and wakefulness revealed that 16p11.2 del/+ males, but not females, spent a significantly greater proportion of wake time in long bouts of consolidated wakefulness (greater than 42 min in duration) compared to controls. These changes in hyperactivity, wake time, and wake time distribution in the males resemble sleep disturbances observed in human ASD and ADHD patients, suggesting that the 16p11.2 del/+ mouse model may be a useful genetic model for studying sleep and activity problems in human neurodevelopmental disorders. Autism Res 2016. © 2016 International Society for Autism Research, Wiley Periodicals, Inc. Autism Res 2017, 10: 572-584. © 2016 International Society for Autism Research, Wiley Periodicals, Inc.

Is the Risk of Autism in Younger Siblings of Affected Children Moderated by Sex, Race/Ethnicity, or Gestational Age?

OBJECTIVE

To evaluate the recurrence risk of autism spectrum disorders (ASD) in younger siblings of affected children and determine how it is modified by race/ethnicity and sex.

METHOD

Medical records of children born in a large health maintenance organization (Kaiser Permanent Southern California) hospitals from January 1, 2001, through December 31, 2010, and who remained in our system until 2 to 11 years of age were used to assess the risk of recurrence of ASD in younger siblings. Children born at <28 or >42 weeks gestation, multiple births, or those who were not active members for ≥3 months were excluded. ASD diagnosis was ascertained from DSM-IV codes, and the magnitude of the association was estimated using adjusted relative risks (aRRs).

RESULTS

Among eligible younger siblings, 592 (1.11%) had the diagnosis of ASD. The ASD rates were 11.30% and 0.92% for younger siblings of older affected and unaffected siblings, respectively (aRR: 14.27; 95% confidence interval, 11.41-17.83). This association remained after adjusting for potential confounding factors. Race/ethnicity- and gestational age-specific analyses revealed a positive association of similar magnitude across groups. Risk remained higher in younger boys than girls regardless of the sex of affected older siblings.

CONCLUSION

The findings of this study suggest that the risk of ASD in younger siblings is higher if the older sibling has ASD. The risk of ASD in younger siblings of older affected siblings was comparable across gestational age at birth and child's race/ethnicity groups. However, risk remains higher for boys. This study contributes to a better understanding of the influence of race/ethnicity, sex, and gestational age at birth in identifying children at higher risk of ASD.

Severity of ASD symptoms and their correlation with the presence of copy number variations and exposure to first trimester ultrasound

Current research suggests that incidence and heterogeneity of autism spectrum disorder (ASD) symptoms may arise through a variety of exogenous and/or endogenous factors. While subject to routine clinical practice and generally considered safe, there exists speculation, though no human data, that diagnostic ultrasound may also contribute to ASD severity, supported by experimental evidence that exposure to ultrasound early in gestation could perturb brain development and alter behavior. Here we explored a modified triple hit hypothesis [Williams & Casanova, ] to assay for a possible relationship between the severity of ASD symptoms and (1) ultrasound exposure (2) during the first trimester of pregnancy in fetuses with a (3) genetic predisposition to ASD. We did so using retrospective analysis of data from the SSC (Simon's Simplex Collection) autism genetic repository funded by the Simons Foundation Autism Research Initiative. We found that male children with ASD, copy number variations (CNVs), and exposure to first trimester ultrasound had significantly decreased non-verbal IQ and increased repetitive behaviors relative to male children with ASD, with CNVs, and no ultrasound. These data suggest that heterogeneity in ASD symptoms may result, at least in part, from exposure to diagnostic ultrasound during early prenatal development of children with specific genetic vulnerabilities. These results also add weight to on-going concerns expressed by the FDA about non-medical use of diagnostic ultrasound during pregnancy. Autism Res 2017, 10: 472-484. © 2016 International Society for Autism Research, Wiley Periodicals, Inc.

Advancing the understanding of autism disease mechanisms through genetics

Progress in understanding the genetic etiology of autism spectrum disorders (ASD) has fueled remarkable advances in our understanding of its potential neurobiological mechanisms. Yet, at the same time, these findings highlight extraordinary causal diversity and complexity at many levels ranging from molecules to circuits and emphasize the gaps in our current knowledge. Here we review current understanding of the genetic architecture of ASD and integrate genetic evidence, neuropathology and studies in model systems with how they inform mechanistic models of ASD pathophysiology. Despite the challenges, these advances provide a solid foundation for the development of rational, targeted molecular therapies.

Sex-Related Cognitive Profile in Autism Spectrum Disorders Diagnosed Late in Life: Implications for the Female Autistic Phenotype

Females with high-functioning ASD are known to camouflage their autistic symptoms better than their male counterparts, making them prone to being under-ascertained and delayed in diagnostic assessment. Thus far the underlying cognitive processes that enable such successful socio-communicative adaptation are not well understood. The current results show sex-related differences in the cognitive profile of ASD individuals, which were diagnosed late in life exclusively. Higher verbal abilities were found in males (n = 69) as opposed to higher processing speed and better executive functions in females with ASD (n = 38). Since both sexes remained unidentified during childhood and adolescence, these results are suggestive for sex-distinctive cognitive strategies as an alternative to typically-developed reciprocal social behavior and social mimicry in high functioning ASD.

Sex bias in autism spectrum disorder in neurofibromatosis type 1

Background

Despite extensive literature, little is known about the mechanisms underlying sex bias in autism spectrum disorder (ASD). This study investigates the sex differences in ASD associated with neurofibromatosis type 1, a single-gene model of syndromic autism.

Methods

We analysed data from n = 194 children aged 4–16 years with neurofibromatosis type 1. Sex differences were evaluated across the Autism Diagnostic Interview-Revised (ADI-R), Autism Diagnostic Observation Schedule (ADOS), verbal IQ, Social Responsiveness Scale (SRS) and Conners questionnaires.

Results

There was 2.68:1 male:female ratio in children meeting ASD criteria on the deep phenotyping measures. On symptom profile, males with neurofibromatosis type 1 (NF1) + ASD were more impaired on reciprocal social interaction and communication domains of the ADI-R but we found no differences on the restricted, repetitive behaviours (RRBs) domain of the ADI-R and no differences on the social on the ADOS. NF1 ASD males and females were comparable on verbal IQ, and the inattention/hyperactivity domains of the Conners questionnaire.

Conclusions

There is a significant male bias in the prevalence of ASD in NF1. The phenotypic profile of NF1 + ASD cases includes greater social communication impairment in males. We discuss the implications of our findings and the rationale for using NF1 as a model for investigating sex bias in idiopathic ASD.

Default Mode Hypoconnectivity Underlies a Sex-Related Autism Spectrum

Background

Females and males differ significantly in the prevalence and presentation of autism spectrum conditions. One theory of this effect postulates that autistic traits lie on a sex-related continuum in the general population, and autism represents the extreme male end of this spectrum. This theory predicts that any feature of autism in males should 1) be present in autistic females, 2) differentiate between the sexes in the typical population, and 3) correlate with autistic traits. We tested these three predictions for default mode network (DMN) hypoconnectivity during the resting state, one of the most robustly found neurobiological differences in autism.

Methods

We analyzed a primary dataset of adolescents (N = 121, 12–18 years of age) containing a relatively large number of females and a replication multisite dataset including children, adolescents, and adults (N = 980, 6–58 years of age). We quantified the average connectivity between DMN regions and tested for group differences and correlation with behavioral performance using robust regression.

Results

We found significant differences in DMN intraconnectivity between female controls and females with autism (p = .001 in the primary dataset; p = .009 in the replication dataset), and between female controls and male controls (p = .036 in the primary dataset; p = .002 in the replication dataset). We also found a significant correlation between DMN intraconnectivity and performance on a mentalizing task (p = .001) in the primary dataset.

Conclusions

Collectively, these findings provide the first evidence for DMN hypoconnectivity as a behaviorally relevant neuroimaging phenotype of the sex-related spectrum of autistic traits, of which autism represents the extreme case.

Commentary: sex difference differences? A reply to Constantino

Messinger et al. found a 3.18 odds ratio of male to female ASD recurrence in 1241 prospectively followed high-risk (HR) siblings. Among high-risk siblings (with and without ASD), as well as among 583 low-risk controls, girls exhibited higher performance on the Mullen Scales of Early Learning, as well as lower restricted and repetitive behavior severity scores on the Autism Diagnostic Observation Schedule (ADOS) than boys. That is, female-favoring sex differences in developmental performance and autism traits were evident among low-risk and non-ASD high-risk children, as well as those with ASD. Constantino (Mol Autism) suggests that sex differences in categorical ASD outcomes in Messinger et al. should be understood as a female protective effect. We are receptive to Constantino’s (Mol Autism) suggestion, and propose that quantitative sex differences in autism-related features are keys to understanding this female protective effect.

The landscape of DNA methylation amid a perfect storm of autism aetiologies

Increasing evidence points to a complex interplay between genes and the environment in autism spectrum disorder (ASD), including rare de novo mutations in chromatin genes such as methyl-CpG binding protein 2 (MECP2) in Rett syndrome. Epigenetic mechanisms such as DNA methylation act at this interface, reflecting the plasticity in metabolic and neurodevelopmentally regulated gene pathways. Genome-wide studies of gene sequences, gene pathways and DNA methylation are providing valuable mechanistic insights into ASD. The dynamic developmental landscape of DNA methylation is vulnerable to numerous genetic and environmental insults: therefore, understanding pathways that are central to this 'perfect storm' will be crucial to improving the diagnosis and treatment of ASD.

Is There a Female Protective Effect Against Attention-Deficit/Hyperactivity Disorder? Evidence From Two Representative Twin Samples

OBJECTIVE

Attention-deficit/hyperactivity disorder (ADHD) is more frequent in males than in females. The "female protective effect" posits that females undergo greater exposure to etiological factors than males in order to develop ADHD, leading to the prediction that relatives of females with ADHD will display more ADHD behaviors. We thus tested whether cotwins of females displaying extreme ADHD traits would display more ADHD traits than cotwins of males displaying extreme ADHD traits.

METHOD

Parents of approximately 7,000 pairs of nonidentical twins in Sweden, and approximately 4,000 pairs of twins in England and Wales, completed dimensional assessments of ADHD traits. Probands were selected on the basis of scoring within the highest 10% of the distribution in each sample. Dimensional scores of cotwins of probands, as well as the categorical recurrence rate, were investigated by proband sex.

RESULTS

Cotwins of female probands displayed higher mean ADHD trait scores (mean = 0.62-0.79) than cotwins of male probands (mean = 0.38-0.55) in both samples. This trend was significant in the Swedish sample (p < .01) and when the 2 samples were merged into a single, larger sample (p < .001). When the samples were merged, there was also a significant association between proband sex and cotwin's categorical status, with more cotwins of female probands also being probands than cotwins of male probands.

CONCLUSION

These findings support a female protective effect against ADHD behaviors, suggesting that females require greater exposure to genetic and environmental factors associated with ADHD in order to develop the condition.

Female Autism Phenotypes Investigated at Different Levels of Language and Developmental Abilities

This study investigated the differences in clinical symptoms between females and males with autism spectrum disorder (ASD) across three verbal ability groups (nonverbal, phrase and fluent speech), based on which Autism Diagnostic Observation Schedule module was administered to 5723 individuals in four research datasets. In the Simons Simplex Collection and Autism Treatment Network, females with ASD and phrase or fluent speech had lower cognitive, adaptive, and social abilities than males. In the Autism Genetics Resource Exchange and the Autism Consortium, females with phrase or fluent speech had similar or better adaptive and social abilities than males. Females who were nonverbal had similar cognitive, adaptive, and social abilities as males. Population-based longitudinal studies of verbally fluent females with ASD are needed.

Gender differences in CNV burden do not confound schizophrenia CNV associations

Compared with the general population, an excess of rare copy number variants (CNVs) has been identified in people with schizophrenia. Females with neurodevelopmental disorders and in the general population have been reported to carry more large, rare CNVs than males. Given that many schizophrenia datasets do not have equal gender ratios in cases and controls, sex differences in CNV burden might have impacted on estimates of case-related CNV burden and also on associations to individual loci. In a sample of 13,276 cases and 17,863 controls, we observed a small but significant excess of large (≥500 Kb), rare (<1%) CNVs in females compared with males in both cases and controls (OR = 1.17, P = 0.0012 for controls; OR = 1.11, P = 0.045 for cases). The burden of 11 schizophrenia-associated CNVs was significantly higher in female cases compared with male cases (OR = 1.38, P = 0.0055), but after accounting for the rates of CNVs in controls, we found no significant gender difference in the risk conferred by these loci. Controlling for gender had a negligible effect on the significance of association between specific CNVs and schizophrenia. The female excess of large CNVs in both cases and controls suggests a female protective mechanism exists for deleterious CNVs that may extend beyond neurodevelopmental phenotypes.

Effects of advanced paternal age on trajectories of social behavior in offspring

Our study is the first investigation of the effects of advanced paternal age (APA) on the developmental trajectory of social behavior in rodent offspring. Given the strong epidemiological association between APA and sexually dimorphic neurodevelopmental disorders that are characterized by abnormalities in social behavior (autism, schizophrenia), we assessed sociability in male and female inbred mice (C57BL/6J) across postnatal development (N = 104) in relation to paternal age. We found differences in early social behavior in both male and female offspring of older breeders, with differences in this social domain persisting into adulthood in males only. We showed that these social deficits were not present in the fathers of these offspring, confirming a de novo origin of an altered social trajectory in the offspring generation. Our results, highly novel in rodent research, support the epidemiological observations in humans and provide evidence for a causal link between APA, age-related changes in the paternal sperm DNA and neurodevelopmental disorders in their offspring.

Recent advances in the genetics of autism spectrum disorder

Autism spectrum disorder (ASD) is a devastating neurodevelopmental disorder with high prevalence in the population and a pronounced male preponderance. ASD has a strong genetic basis, but until recently, a large fraction of the genetic factors contributing to liability was still unknown. Over the past 3 years, high-throughput next-generation sequencing on large cohorts has exposed a heterogeneous and complex genetic landscape and has revealed novel risk genes. Here, we provide an overview of the recent advances on the ASD genetic architecture, with an emphasis on the estimates of heritability, the contribution of common variants, and the role of inherited and de novo rare variation. We also examine the genetic components of the reported gender bias. Finally, we discuss the emerging findings from sequencing studies and how they illuminate crucial aspects of ASD pathophysiology.

The Evolving Diagnostic and Genetic Landscapes of Autism Spectrum Disorder

The autism spectrum disorders (ASD) are a heterogeneous set of neurodevelopmental syndromes defined by impairments in verbal and non-verbal communication, restricted social interaction, and the presence of stereotyped patterns of behavior. The prevalence of ASD is rising, and the diagnostic criteria and clinical perspectives on the disorder continue to evolve in parallel. Although the majority of individuals with ASD will not have an identifiable genetic cause, almost 25% of cases have identifiable causative DNA variants. The rapidly improving ability to identify genetic mutations because of advances in next generation sequencing, coupled with previous epidemiological studies demonstrating high heritability of ASD, have led to many recent attempts to identify causative genetic mutations underlying the ASD phenotype. However, although hundreds of mutations have been identified to date, they are either rare variants affecting only a handful of ASD patients, or are common variants in the general population conferring only a small risk for ASD. Furthermore, the genes implicated thus far are heterogeneous in their structure and function, hampering attempts to understand shared molecular mechanisms among all ASD patients; an understanding that is crucial for the development of targeted diagnostics and therapies. However, new work is beginning to suggest that the heterogeneous set of genes implicated in ASD may ultimately converge on a few common pathways. In this review, we discuss the parallel evolution of our diagnostic and genetic understanding of autism spectrum disorders, and highlight recent attempts to infer common biology underlying this complicated syndrome.

Microduplications at the pseudoautosomal SHOX locus in autism spectrum disorders and related neurodevelopmental conditions

BACKGROUND

The pseudoautosomal short stature homeobox-containing (SHOX) gene encodes a homeodomain transcription factor involved in cell-cycle and growth regulation. SHOX/SHOX enhancers deletions cause short stature and skeletal abnormalities in a female-dominant fashion; duplications appear to be rare. Neurodevelopmental disorders (NDDs), such as autism spectrum disorders (ASDs), are complex disorders with high heritability and skewed sex ratio; several rare (<1% frequency) CNVs have been implicated in risk.

METHODS

We analysed data from a discovery series of 90 adult ASD cases, who underwent clinical genetic testing by array-comparative genomic hybridisation (CGH). Twenty-seven individuals harboured CNV abnormalities, including two unrelated females with microduplications affecting SHOX. To determine the prevalence of SHOX duplications and delineate their associated phenotypic spectrum, we subsequently examined array-CGH data from a follow-up sample of 26 574 patients, including 18 857 with NDD (3541 with ASD).

RESULTS

We found a significant enrichment of SHOX microduplications in the NDD cases (p=0.00036; OR 2.21) and, particularly, in those with ASD (p=9.18×10(-7); OR 3.63) compared with 12 594 population-based controls. SHOX duplications affecting the upstream or downstream enhancers were enriched only in females with NDD (p=0.0043; OR 2.69/p=0.00020; OR 7.20), but not in males (p=0.404; OR 1.38/p=0.096; OR 2.21).

CONCLUSIONS

Microduplications at the SHOX locus are a low penetrance risk factor for ASD/NDD, with increased risk in both sexes. However, a concomitant duplication of SHOX enhancers may be required to trigger a NDD in females. Since specific SHOX isoforms are exclusively expressed in the developing foetal brain, this may reflect the pathogenic effect of altered SHOX protein dosage on neurodevelopment.

Self-Reported Empathy in Adult Women with Autism Spectrum Disorders - A Systematic Mini Review

INTRODUCTION

There is limited research on Autism Spectrum Disorders (ASD) in females. Although the empathy construct has been examined thoroughly in autism, little attention has been paid to empathy in adult women with this condition or to gender differences within the disorder.

OBJECTIVE

Self-reported empathy in adult women with ASD was examined and compared to that of typically developed men and women as well as to men with this condition.

METHODS

Online databases were searched for articles investigating self-reported empathy among adult women with ASD. Only six studies comparing women to men were identified.

RESULTS

All studies found women with an ASD to report lower levels of empathy than typically developed women, and typically developed men, but similar levels to men with this condition.

CONCLUSION

The self-reported empathic ability of women diagnosed with ASD resembles that of their male counterparts most closely; they show a hypermasculinisation in empathy. This is particularly surprising considering the large gender difference in empathy in the general population.

DISCUSSION

One of the limitations of this review is that the current diagnostic criteria for ASD are oriented towards male-specific behaviour and fail to integrate gender specific characteristics. Hence, women diagnosed with ASD are likely to be at the male end of the continuum. The suggested hypermasculinisation of women on the spectrum, as evident from this review, may therefore be exaggerated due to a selection bias.

Sex differences in autism: a resting-state fMRI investigation of functional brain connectivity in males and females

Autism spectrum disorders (ASD) are far more prevalent in males than in females. Little is known however about the differential neural expression of ASD in males and females. We used a resting-state fMRI-dataset comprising 42 males/42 females with ASD and 75 male/75 female typical-controls to examine whether autism-related alterations in intrinsic functional connectivity are similar or different in males and females, and particularly whether alterations reflect 'neural masculinization', as predicted by the Extreme Male Brain theory. Males and females showed a differential neural expression of ASD, characterized by highly consistent patterns of hypo-connectivity in males with ASD (compared to typical males), and hyper-connectivity in females with ASD (compared to typical females). Interestingly, patterns of hyper-connectivity in females with ASD reflected a shift towards the (high) connectivity levels seen in typical males (neural masculinization), whereas patterns of hypo-connectivity observed in males with ASD reflected a shift towards the (low) typical feminine connectivity patterns (neural feminization). Our data support the notion that ASD is a disorder of sexual differentiation rather than a disorder characterized by masculinization in both genders. Future work is needed to identify underlying factors such as sex hormonal alterations that drive these sex-specific neural expressions of ASD.

Enhanced Social Attention in Female Infant Siblings at Risk for Autism

OBJECTIVE

Sexual dimorphism in autism spectrum disorders (ASD) is a well-recognized but poorly understood phenomenon. Females are four times less likely to be diagnosed with ASD than males and, when diagnosed, are more likely to exhibit comorbid anxiety symptoms. One of the key phenotypic features of ASD is atypical attention to socially relevant stimuli. Eye-tracking studies indicate atypical patterns of spontaneous social orienting during the prodromal and early syndromic stages of ASD. However, there have been no studies evaluating sex differences in early social orienting and their potential contribution to later outcomes.

METHOD

We examined sex differences in social orienting in 6-, 9-, and 12-month-old infants at high genetic risk for ASD (n = 101) and in low-risk controls (n = 61), focusing on neurobehavioral measures of function across a spectrum of autism risk.

RESULTS

Results suggest that, between 6 and 12 months of age, a period highly consequential for the development of nonverbal social engagement competencies, high-risk females show enhanced attention to social targets, including faces, compared to both high-risk males and low-risk males and females. Greater attention to social targets in high-risk infants was associated with less severe social impairments at 2 years.

CONCLUSION

The results suggest an alternative expression of autism risk in females, which manifests in infancy as increased attention toward socially relevant stimuli. This increased attention may serve as a female protective factor against ASD by providing increased access to social experiences in early development.

Gene expression in human brain implicates sexually dimorphic pathways in autism spectrum disorders

Autism spectrum disorder (ASD) is more prevalent in males, and the mechanisms behind this sex-differential risk are not fully understood. Two competing, but not mutually exclusive, hypotheses are that ASD risk genes are sex-differentially regulated, or alternatively, that they interact with characteristic sexually dimorphic pathways. Here we characterized sexually dimorphic gene expression in multiple data sets from neurotypical adult and prenatal human neocortical tissue, and evaluated ASD risk genes for evidence of sex-biased expression. We find no evidence for systematic sex-differential expression of ASD risk genes. Instead, we observe that genes expressed at higher levels in males are significantly enriched for genes upregulated in post-mortem autistic brain, including astrocyte and microglia markers. This suggests that it is not sex-differential regulation of ASD risk genes, but rather naturally occurring sexually dimorphic processes, potentially including neuron–glial interactions, that modulate the impact of risk variants and contribute to the sex-skewed prevalence of ASD.

Autism spectrum disorder is approximately 4.5 times more likely to occur in boys than girls. Here, Werling, Geschwind and Parikshak characterized sexually dimorphic gene expression in the non-diseased, post-mortem, adult and prenatal human brain, and show genes expressed at higher levels in males are significantly enriched for genes upregulated in autistic brain.

A Short Review on the Current Understanding of Autism Spectrum Disorders

Autism spectrum disorder (ASD) is a set of neurodevelopmental disorders characterized by a deficit in social behaviors and nonverbal interactions such as reduced eye contact, facial expression, and body gestures in the first 3 years of life. It is not a single disorder, and it is broadly considered to be a multi-factorial disorder resulting from genetic and non-genetic risk factors and their interaction. Genetic studies of ASD have identified mutations that interfere with typical neurodevelopment in utero through childhood. These complexes of genes have been involved in synaptogenesis and axon motility. Recent developments in neuroimaging studies have provided many important insights into the pathological changes that occur in the brain of patients with ASD in vivo. Especially, the role of amygdala, a major component of the limbic system and the affective loop of the cortico-striatothalamo-cortical circuit, in cognition and ASD has been proved in numerous neuropathological and neuroimaging studies. Besides the amygdala, the nucleus accumbens is also considered as the key structure which is related with the social reward response in ASD. Although educational and behavioral treatments have been the mainstay of the management of ASD, pharmacological and interventional treatments have also shown some benefit in subjects with ASD. Also, there have been reports about few patients who experienced improvement after deep brain stimulation, one of the interventional treatments. The key architecture of ASD development which could be a target for treatment is still an uncharted territory. Further work is needed to broaden the horizons on the understanding of ASD.

Effect of co-twin gender on neurodevelopmental symptoms: a twin register study

BACKGROUND

Autism spectrum disorder (ASD) and attention-deficit/hyperactivity disorder (ADHD) are neurodevelopmental disorders thought to have both genetic and environmental causes. It has been hypothesized that exposure to elevated levels of prenatal testosterone is associated with elevated traits of ASD and ADHD. Assuming that testosterone levels from a dizygotic male twin fetus may lead to enhanced testosterone exposure of its co-twins, we aimed to test the prenatal testosterone hypothesis by comparing same-sex with opposite-sex dizygotic twins with respect to neurodevelopmental symptoms.

METHODS

Neuropsychiatric traits were assessed in a population-based twin cohort from the Child and Adolescent Twin Study in Sweden (CATSS). Parental interviews were conducted for 16,312 dizygotic twins, 9 and 12 years old, with the Autism-Tics, ADHD, and other Comorbidities inventory (A-TAC).

RESULTS

Girls with a female co-twin had an increased risk of reaching the cut-off score for ADHD compared with girls with a male co-twin. Both boys and girls with a female co-twin displayed a larger number of traits related to attention deficit and repetitive and stereotyped behaviors than those with a male twin. In girls, this also extended to social interaction and the combined measures for ASD and ADHD, however, with small effect sizes.

CONCLUSIONS

Our results are reverse to what would have been expected from the prenatal testosterone hypothesis but consistent with a previous study of ASD and ADHD traits in dizygotic twins. The seemingly protective effect for girls of having a twin brother may be an effect of parent report bias, but may also be an unexpected effect of sharing the intrauterine environment with a male co-twin.

Longitudinal comparison between male and female preschool children with autism spectrum disorder

Epidemiological studies have highlighted a strong male bias in autism spectrum disorder (ASD), however few studies have examined gender differences in autism symptoms, and available findings are inconsistent. The aim of the present study is to investigate the longitudinal gender differences in developmental profiles of 30 female and 30 male age-matched preschool children with ASD. All the children underwent a comprehensive evaluation at T0 and at T1. Our results have shown no significant interaction between time and gender for predicting autism symptoms, developmental quotient, parental stress, children's adaptive skills and behavior problems. Shedding light on the developmental trajectories in ASD could help clinicians to recognize children with ASD at an earlier age and contribute to the development of appropriate treatments.

Summaries of plenary, symposia, and oral sessions at the XXII World Congress of Psychiatric Genetics, Copenhagen, Denmark, 12-16 October 2014

The XXII World Congress of Psychiatric Genetics, sponsored by the International Society of Psychiatric Genetics, took place in Copenhagen, Denmark, on 12-16 October 2014. A total of 883 participants gathered to discuss the latest findings in the field. The following report was written by student and postdoctoral attendees. Each was assigned one or more sessions as a rapporteur. This manuscript represents topics covered in most, but not all of the oral presentations during the conference, and contains some of the major notable new findings reported.

Can Sibling Sex Ratios Be Used as a Valid Test for the Prenatal Androgen Hypothesis of Autism Spectrum Disorders?

BACKGROUND

Sibling sex ratios have been applied as an indirect test of a hypothesized association between prenatal testosterone levels and risk for autism, a developmental disorder disproportionately affecting males. Differences in sibling sex ratios between those with and without autism would provide evidence of a shared risk factor for autism and offspring sex. Conclusions related to prenatal testosterone, however, require additional assumptions. Here, we used directed acyclic graphs (DAGs) to clarify the elements required for a valid test of the hypothesis that sibling sex ratios differ between children with and without autism. We then conducted such a test using a large, population-based sample of children.

METHODS

Over 1.1 million subjects, born in California from 1992-2007, and identified through birth records, were included. The association between autism diagnosis, determined using the administrative database of the California Department of Developmental Services, and the sex of the subsequent sibling was examined using generalized estimating equations. Sources of potential bias identified using DAGs were addressed.

RESULTS

Among male children with autism, 52.2% of next-born siblings were brothers, versus 51.0% for unaffected males. For females with autism, 50.2% of following siblings were brothers versus 51.2% among control females. The relative risk of a subsequent male sibling associated with autism diagnosis was 1.02 (95% confidence interval: 0.99, 1.04).

CONCLUSIONS

In a large, population-based sample we failed to find evidence suggesting an excess of brothers among children with autism while controlling for several threats to validity. This test cannot rule out a role of any given exposure, including prenatal testosterone, in either risk of autism or offspring sex ratio, but suggests against a common cause of both.

Quantitative autism symptom patterns recapitulate differential mechanisms of genetic transmission in single and multiple incidence families

BACKGROUND

Previous studies have demonstrated aggregation of autistic traits in undiagnosed family members of children with autism spectrum disorder (ASD), which has significant implications for ASD risk in their offspring. This study capitalizes upon a large, quantitatively characterized clinical-epidemiologic family sample to establish the extent to which family transmission pattern and sex modulate ASD trait aggregation.

METHODS

Data were analyzed from 5515 siblings (2657 non-ASD and 2858 ASD) included in the Interactive Autism Network. Autism symptom levels were measured using the Social Responsiveness Scale (SRS) and by computing Diagnostic and Statistical Manual of Mental Disorders-Fifth Edition (DSM-5) symptom scores based on items from the SRS and Social Communication Questionnaire. Generalized estimating equation models evaluated the influence of family incidence types (single versus multiple incidence families; male-only ASD-affected families versus families with female ASD-affected children), diagnostic group (non-ASD children with and without a history of language delay with autistic speech and ASD-affected children), and sibling sex on ASD symptom levels.

RESULTS

Non-ASD children manifested elevated ASD symptom burden when they were members of multiple incidence families-this effect was accentuated for male children in female ASD-containing families-or when they had a history of language delay with autistic qualities of speech. In this sample, ASD-affected children from multiple incidence families had lower symptom levels than their counterparts in single incidence families. Recurrence risk for ASD was higher for children from female ASD-containing families than for children from male-only families.

CONCLUSIONS

Sex and patterns of family transmission modulate the risk of autism symptom burden in undiagnosed siblings of ASD-affected children. Identification of these symptoms/traits and their molecular genetic causes may have significant implications for genetic counseling and for understanding inherited liabilities that confer risk for ASD in successive generations. Autism symptom elevations were more dramatic in non-ASD children from multiple incidence families and those with a history of language delay and autistic qualities of speech, identifying sub-groups at substantially greater transmission risk. Higher symptom burden and greater recurrence in children from female ASD-containing families indicate that familial aggregation patterns are further qualified by sex-specific thresholds, supportive of the notion that females require a higher burden of deleterious liability to cross into categorical ASD diagnosis.

Etiological overlap between obsessive-compulsive disorder and anorexia nervosa: a longitudinal cohort, multigenerational family and twin study

Obsessive-compulsive disorder (OCD) often co-occurs with anorexia nervosa (AN), a comorbid profile that complicates the clinical management of both conditions. This population-based study aimed to examine patterns of comorbidity, longitudinal risks, shared familial risks and shared genetic factors between OCD and AN at the population level. Participants were individuals with a diagnosis of OCD (N=19,814) or AN (N=8,462) in the Swedish National Patient Register between January 1992 and December 2009; their first-, second- and third-degree relatives; and population-matched (1:10 ratio) unaffected comparison individuals and their relatives. Female twins from the population-based Swedish Twin Register (N=8,550) were also included. Females with OCD had a 16-fold increased risk of having a comorbid diagnosis of AN, whereas males with OCD had a 37-fold increased risk. Longitudinal analyses showed that individuals first diagnosed with OCD had an increased risk for a later diagnosis of AN (risk ratio, RR=3.6), whereas individuals first diagnosed with AN had an even greater risk for a later diagnosis of OCD (RR=9.6). These longitudinal risks were about twice as high for males than for females. First- and second-degree relatives of probands with OCD had an increased risk for AN, and the magnitude of this risk tended to increase with the degree of genetic relatedness. Bivariate twin models revealed a moderate but significant degree of genetic overlap between self-reported OCD and AN diagnoses (ra =0.52, 95% CI: 0.26-0.81), but most of the genetic variance was disorder-specific. The moderately high genetic correlation supports the idea that this frequently observed comorbid pattern is at least in part due to shared genetic factors, though disorder-specific factors are more important. These results have implications for current gene-searching efforts and for clinical practice.

Childhood neurodevelopmental problems and adolescent bully victimization: population-based, prospective twin study in Sweden

Bully victimization is a common problem among children with neurodevelopmental disorders, including attention deficit/hyperactivity disorder and autism spectrum disorder. Previous research was mostly cross-sectional and seldom accounted for co-morbid psychopathology, which makes it difficult to draw conclusions about causality and specificity of any association. Using a genetically informative prospective design, we investigated the association between various neurodevelopmental problems (NDPs) in childhood and bully victimization in adolescence, and the relative contributions of genetic and environmental factors to this association. We obtained parent-reports of NDPs at age 9/12 years and self-reported bully victimization at age 15 for 3,921 children participating in the The Child and Adolescent Twin Study in Sweden (CATSS). Structural equation modelling was used to control for NDP co-morbidity and bully victimization at baseline. Cholesky decomposition was used to analyse genetic and environmental contributions to observed associations. Because most of the NDPs were associated to later bully victimization, a common effect of all NDPs was summarized into a general NDP factor. Controlling for this general factor, only problems with social interaction and motor control uniquely predicted subsequent bully victimization in girls. General and unique associations were influenced by both genetic and unique environmental factors. NDPs in general and social interaction and motor problems in particular predicted later bully victimization. The longitudinal design and twin analyses indicated that these associations might be causal. Knowledge of these vulnerabilities may be important when designing risk assessment and prevention strategies.

An assessment of sex bias in neurodevelopmental disorders

Background

Neurodevelopmental disorders such as autism and intellectual disability have a sex bias skewed towards boys; however, systematic assessment of this bias is complicated by the presence of significant genetic and phenotypic heterogeneity of these disorders.

Methods

To assess the extent and characteristics of sex bias, we analyzed the frequency of comorbid features, the magnitude of genetic load, and the existence of family history within 32,155 individuals ascertained clinically for autism or intellectual disability/developmental delay (ID/DD), including a subset of 8,373 individuals carrying rare copy-number variants (CNVs).

Results

We find that girls were more likely than boys to show comorbid features within both autism (P = 2.9 × 10⁻⁶, OR = 1.34) and ID/DD (P = 7.2 × 10⁻⁴, OR = 1.08) cohorts. The frequency of comorbid features in ID/DD was higher in boys (1q21.1 deletion, 15q11.2q13.1 duplication) or girls (15q13.3 deletion, 16p11.2 deletion) carrying specific CNVs associated with variable expressivity while such differences were the smallest for syndromic CNVs (Smith-Magenis syndrome, DiGeorge syndrome). The extent of the male sex bias also varied according to the specific comorbid feature, being most extreme for autism with psychiatric comorbidities and least extreme for autism comorbid with epilepsy. The sex ratio was also specific to certain CNVs, from an 8:1 male:female ratio observed among autistic individuals carrying the 22q11.2 duplication to 1.3:1 male:female ratio in those carrying the 16p11.2 deletion. Girls carried a higher burden of large CNVs compared to boys for autism or ID/DD, and this difference diminished when severe comorbidities were considered. Affected boys showed a higher frequency of neuropsychiatric family histories such as autism (P = 0.01) or specific learning disability (P = 0.03), while affected girls showed a higher frequency of developmental family histories such as growth abnormalities (P = 0.02).

Conclusions

The sex bias within neurodevelopmental disorders is influenced by the presence of specific comorbidities, specific CNVs, mutational burden, and pre-existing family history of neurodevelopmental phenotypes.

Electronic supplementary material

The online version of this article (doi:10.1186/s13073-015-0216-5) contains supplementary material, which is available to authorized users.

Variation in the X-linked EFHC2 gene is associated with social cognitive abilities in males

Females outperform males on many social cognitive tasks. X-linked genes may contribute to this sex difference. Males possess one X chromosome, while females possess two X chromosomes. Functional variations in X-linked genes are therefore likely to impact more on males than females. Previous studies of X-monosomic women with Turner syndrome suggest a genetic association with facial fear recognition abilities at Xp11.3, specifically at a single nucleotide polymorphism (SNP rs7055196) within the EFHC2 gene. Based on a strong hypothesis, we investigated an association between variation at SNP rs7055196 and facial fear recognition and theory of mind abilities in males. As predicted, males possessing the G allele had significantly poorer facial fear detection accuracy and theory of mind abilities than males possessing the A allele (with SNP variant accounting for up to 4.6% of variance). Variation in the X-linked EFHC2 gene at SNP rs7055196 is therefore associated with social cognitive abilities in males.

Sex and gender differences in autism spectrum disorder: summarizing evidence gaps and identifying emerging areas of priority

One of the most consistent findings in autism spectrum disorder (ASD) research is a higher rate of ASD diagnosis in males than females. Despite this, remarkably little research has focused on the reasons for this disparity. Better understanding of this sex difference could lead to major advancements in the prevention or treatment of ASD in both males and females. In October of 2014, Autism Speaks and the Autism Science Foundation co-organized a meeting that brought together almost 60 clinicians, researchers, parents, and self-identified autistic individuals. Discussion at the meeting is summarized here with recommendations on directions of future research endeavors.

Sex and gender differences in autism spectrum disorder: summarizing evidence gaps and identifying emerging areas of priority

One of the most consistent findings in autism spectrum disorder (ASD) research is a higher rate of ASD diagnosis in males than females. Despite this, remarkably little research has focused on the reasons for this disparity. Better understanding of this sex difference could lead to major advancements in the prevention or treatment of ASD in both males and females. In October of 2014, Autism Speaks and the Autism Science Foundation co-organized a meeting that brought together almost 60 clinicians, researchers, parents, and self-identified autistic individuals. Discussion at the meeting is summarized here with recommendations on directions of future research endeavors.

Prenatal Programming of Postnatal Susceptibility to Memory Impairments: A Developmental Double Jeopardy

In the study reported here, we examined the effects of fetal exposure to a synthetic stress hormone (synthetic glucocorticoids) on children's susceptibility to postnatal sociodemographic adversity. We recruited children who were born healthy and at term. Twenty-six had been treated with steroid hormones (glucocorticoids) during the prenatal period, and 85 had not. Only children exposed to both prenatal stress hormones and postnatal sociodemographic adversity showed impaired performance on standardized tests of memory function. The association was specific to long-term memory. General intellectual functioning and expressive language were not affected by fetal glucocorticoid exposure. Results were independent of maternal intelligence and maternal depression at the time of the study. These findings are consistent with a vulnerability-stress model: Prenatal exposure to synthetic stress hormones is associated with increased susceptibility to subsequent adversity, with consequences for cognitive functioning that persist 6 to 10 years after birth.

Sex-different abnormalities in the right second to fourth digit ratio in Japanese individuals with autism spectrum disorders

Background

The prevalence of autism spectrum disorders (ASDs) is higher in men than in women. The extreme male brain theory proposes that excessive prenatal testosterone activity could be a risk factor for ASDs. However, it is unclear whether prenatal sex hormone activity is a risk factor for women. The ratio of the length of the second to fourth digits (2D:4D) is considered to be a biomarker of the prenatal ratio of testosterone to estrogen. Therefore, this study compared the 2D:4D ratios of women with and without ASDs to determine if prenatal sex hormone activity could be a risk factor for ASDs in women.

Methods

The study included 35 Japanese men with ASDs, 17 Japanese women with ASDs, 59 typically developed (TD) Japanese men, and 57 TD Japanese women. We measured digit lengths and compared the 2D:4D ratios among the four groups. We also examined the relationship between the 2D:4D ratio and the autism-spectrum quotient score of each group.

Results

In our cohort, men with ASDs tended to have lower right-hand 2D:4D ratios relative to TD men. In contrast, the right 2D:4D ratios in women with ASDs were higher compared to those of TD women. No significant correlations were found between the 2D:4D ratios and the autism-spectrum quotient scores in any group. The higher right 2D:4D ratios in women could not be explained by age or full-scale intelligent quotients. This group difference was not found for the left 2D:4D or right–left 2D:4D ratios.

Conclusions

We found a reverse direction of abnormality in the right 2D:4D ratio for men and women with ASDs. It has been posited that high prenatal testosterone levels lead to a lower 2D:4D ratio. However, a recent animal study showed that testosterone injection to dam leads to a higher right 2D:4D ratio especially for female offspring, which might be mediated by abnormal adipose accumulation in the fingertip. Therefore, the present findings suggest that high prenatal testosterone could be a risk factor both for Japanese men and women with ASDs, elucidating one potential etiology of ASDs in women.

Sex differences in brain plasticity: a new hypothesis for sex ratio bias in autism

Several observations support the hypothesis that differences in synaptic and regional cerebral plasticity between the sexes account for the high ratio of males to females in autism. First, males are more susceptible than females to perturbations in genes involved in synaptic plasticity. Second, sex-related differences in non-autistic brain structure and function are observed in highly variable regions, namely, the heteromodal associative cortices, and overlap with structural particularities and enhanced activity of perceptual associative regions in autistic individuals. Finally, functional cortical reallocations following brain lesions in non-autistic adults (for example, traumatic brain injury, multiple sclerosis) are sex-dependent. Interactions between genetic sex and hormones may therefore result in higher synaptic and consecutively regional plasticity in perceptual brain areas in males than in females. The onset of autism may largely involve mutations altering synaptic plasticity that create a plastic reaction affecting the most variable and sexually dimorphic brain regions. The sex ratio bias in autism may arise because males have a lower threshold than females for the development of this plastic reaction following a genetic or environmental event.

Early sex differences are not autism-specific: A Baby Siblings Research Consortium (BSRC) study

BACKGROUND

The increased male prevalence of autism spectrum disorder (ASD) may be mirrored by the early emergence of sex differences in ASD symptoms and cognitive functioning. The female protective effect hypothesis posits that ASD recurrence and symptoms will be higher among relatives of female probands. This study examined sex differences and sex of proband differences in ASD outcome and in the development of ASD symptoms and cognitive functioning among the high-risk younger siblings of ASD probands and low-risk children.

METHODS

Prior to 18 months of age, 1824 infants (1241 high-risk siblings, 583 low-risk) from 15 sites were recruited. Hierarchical generalized linear model (HGLM) analyses of younger sibling and proband sex differences in ASD recurrence among high-risk siblings were followed by HGLM analyses of sex differences and group differences (high-risk ASD, high-risk non-ASD, and low-risk) on the Mullen Scales of Early Learning (MSEL) subscales (Expressive and Receptive Language, Fine Motor, and Visual Reception) at 18, 24, and 36 months and Autism Diagnostic Observation Schedule (ADOS) domain scores (social affect (SA) and restricted and repetitive behaviors (RRB)) at 24 and 36 months.

RESULTS

Of 1241 high-risk siblings, 252 had ASD outcomes. Male recurrence was 26.7 % and female recurrence 10.3 %, with a 3.18 odds ratio. The HR-ASD group had lower MSEL subscale scores and higher RRB and SA scores than the HR non-ASD group, which had lower MSEL subscale scores and higher RRB scores than the LR group. Regardless of group, males obtained lower MSEL subscale scores, and higher ADOS RRB scores, than females. There were, however, no significant interactions between sex and group on either the MSEL or ADOS. Proband sex did not affect ASD outcome, MSEL subscale, or ADOS domain scores.

CONCLUSIONS

A 3.2:1 male:female odds ratio emerged among a large sample of prospectively followed high-risk siblings. Sex differences in cognitive performance and repetitive behaviors were apparent not only in high-risk children with ASD, but also in high-risk children without ASD and in low-risk children. Sex differences in young children with ASD do not appear to be ASD-specific but instead reflect typically occurring sex differences seen in children without ASD. Results did not support a female protective effect hypothesis.

Neurocognitive abilities in the general population and composite genetic risk scores for attention-deficit hyperactivity disorder

BACKGROUND

The genetic architecture of ADHD is complex, with rare and common variants involved. Common genetic variants (as indexed by a composite risk score) associated with clinical ADHD significantly predict ADHD and autistic-like behavioural traits in children from the general population, suggesting that ADHD lies at the extreme of normal trait variation. ADHD and other neurodevelopmental disorders share neurocognitive difficulties in several domains (e.g. impaired cognitive ability and executive functions). We hypothesised that ADHD composite genetic risk scores derived from clinical ADHD cases would also contribute to variation in neurocognitive abilities in the general population.

METHODS

Children (N = 6,832) from a UK population cohort, the Avon Longitudinal Study of Parents and Children (ALSPAC), underwent neurocognitive testing. Parent-reported measures of their children's ADHD and autistic-like traits were used to construct a behavioural latent variable of 'neurodevelopmental traits'. Composite genetic risk scores for ADHD were calculated for ALSPAC children based on findings from an independent ADHD case-control genome-wide association study. Structural equation modelling was used to assess associations between ADHD composite genetic risk scores and IQ, working memory, inhibitory control and facial emotion recognition, as well as the latent 'neurodevelopmental trait' measure.

RESULTS

The results confirmed that neurocognitive and neurodevelopmental traits are correlated in children in the general population. Composite genetic risk scores for ADHD were independently associated with lower IQ (β = -.05, p < .001) and working memory performance (β = -.034, p = .013), even after accounting for the relationship with latent neurodevelopmental behavioural trait scores. No associations were found between composite genetic risk scores and inhibitory control or emotion recognition (p > .05).

CONCLUSIONS

These findings suggest that common genetic variants relevant to clinically diagnosed ADHD have pleiotropic effects on neurocognitive traits as well as behavioural dimensions in the general population. This further suggests that the well-recognised association between cognition and neurodevelopmental behavioural traits is underpinned at a biological level.

Sex differences in multisensory speech processing in both typically developing children and those on the autism spectrum

BACKGROUND

Previous work has revealed sizeable deficits in the abilities of children with an autism spectrum disorder (ASD) to integrate auditory and visual speech signals, with clear implications for social communication in this population. There is a strong male preponderance in ASD, with approximately four affected males for every female. The presence of sex differences in ASD symptoms suggests a sexual dimorphism in the ASD phenotype, and raises the question of whether this dimorphism extends to ASD traits in the neurotypical population. Here, we investigated possible sexual dimorphism in multisensory speech integration in both ASD and neurotypical individuals.

METHODS

We assessed whether males and females differed in their ability to benefit from visual speech when target words were presented under varying levels of signal-to-noise, in samples of neurotypical children and adults, and in children diagnosed with an ASD.

RESULTS

In typically developing (TD) children and children with ASD, females (n = 47 and n = 15, respectively) were significantly superior in their ability to recognize words under audiovisual listening conditions compared to males (n = 55 and n = 58, respectively). This sex difference was absent in our sample of neurotypical adults (n = 28 females; n = 28 males).

CONCLUSIONS

We propose that the development of audiovisual integration is delayed in male relative to female children, a delay that is also observed in ASD. In neurotypicals, these sex differences disappear in early adulthood when females approach their performance maximum and males "catch up." Our findings underline the importance of considering sex differences in the search for autism endophenotypes and strongly encourage increased efforts to study the underrepresented population of females within ASD.

Do women with eating disorders who have social and flexibility difficulties really have autism? A case series

Background

Many women with eating disorders (EDs) have social impairments and difficulties with flexibility. It is unclear to what extent these are manifestations of an underlying autism spectrum disorder (ASD); or whether they are instead the consequence of starvation, anxiety, low mood or obsessive compulsive disorder, all of which are highly prevalent in EDs. The resolution of this clinically and theoretically important uncertainty will require the use of gold-standard ASD assessment measures. To date these have not been employed in ED research. This case series is the first report of a well-validated, direct-observational measure of ASD, the Autism Diagnostic Observation Schedule (ADOS), being administered to women with EDs. We aimed to learn about the feasibility of the ADOS in this population, and to contribute to debates about whether a sub-group with EDs really have ASD.

Methods

Ten women (mean age = 26.4 years, range = 19 to 38 years) who had a suspected ASD due to social and flexibility difficulties and were receiving treatment for ED (seven anorexia, two ED not otherwise specified, one bulimia) at a specialist service (four inpatient, six outpatient) received an ADOS Module 4 assessment.

Results

All 10 participants completed all activities of the ADOS Module 4. Five scored in the ASD range on the ADOS diagnostic algorithm. An additional two were judged likely to have ASD, even though they scored below the ADOS’s diagnostic threshold. This was on the basis of clinical observation, participant self-report and parent report. The seven women who we estimated to have ASD all reported autistic difficulties prior to the onset of their ED. They commonly described longstanding non-autistic neurodevelopmental problems, including dyslexia, dyspraxia and epilepsy. Only one had a childhood diagnosis of ASD.

Conclusions

A substantial proportion of women with EDs who present with social and flexibility difficulties may have an unrecognised ASD, indicated by a constellation of autistic difficulties that appears to predate the onset of their eating problems. The ADOS is a useful component of an ASD assessment for adult women with ED.