Pre-, peri- and neonatal risk factors for autism

Emerging biomarkers in autism spectrum disorder: a systematic review

Autism spectrum disorder (ASD) affects approximately 2% of children in the United States (US) yet its etiology is unclear and effective treatments are lacking. Therapeutic interventions are most effective if started early in life, yet diagnosis often remains delayed, partly because the diagnosis of ASD is based on identifying abnormal behaviors that may not emerge until the disorder is well established. Biomarkers that identify children at risk during the pre-symptomatic period, assist with early diagnosis, confirm behavioral observations, stratify patients into subgroups, and predict therapeutic response would be a great advance. Here we underwent a systematic review of the literature on ASD to identify promising biomarkers and rated the biomarkers in regards to a Level of Evidence and Grade of Recommendation using the Oxford Centre for Evidence-Based Medicine scale. Biomarkers identified by our review included physiological biomarkers that identify neuroimmune and metabolic abnormalities, neurological biomarkers including abnormalities in brain structure, function and neurophysiology, subtle behavioral biomarkers including atypical development of visual attention, genetic biomarkers and gastrointestinal biomarkers. Biomarkers of ASD may be found prior to birth and after diagnosis and some may predict response to specific treatments. Many promising biomarkers have been developed for ASD. However, many biomarkers are preliminary and need to be validated and their role in the diagnosis and treatment of ASD needs to be defined. It is likely that biomarkers will need to be combined to be effective to identify ASD early and guide treatment.

Autism Spectrum Disorders and Perinatal Complications-Is Oxidative Stress the Connection?

Background: Autism spectrum disorders (ASD) are complex psychiatric disorders, with gene environment interaction being in the basis of their etiology. The association of perinatal complications and ASD is well established. Recent findings suggested that oxidative stress and polymorphism in genes encoding antioxidant enzymes might be involved in the development of ASD. Glutathione transferases (GSTs) have an important role in the antioxidant defense system. We aimed to establish whether the predictive effects of prenatal and perinatal complications (as possible oxidative stress inducers) on ASD risk are dependent on GST polymorphisms. Methods: The study included 113 ASD cases and 114 age- and sex group-matched healthy controls. All participants were genotyped for GSTA1, GSTM1, GSTT1, and GSTP1 polymorphisms. The questionnaire regarding prenatal and perinatal risk factors and complications was administered for all the subjects in the study. Results: The evaluated perinatal complications as a group significantly increased the risk of ASD [odds ratio (OR) = 9.415; p = 0.000], as well as individual perinatal complications, such as prematurity (OR = 11.42; p = 0.001), neonatal jaundice (OR = 8.774; p = 0.000), respiratory distress syndrome (OR = 4.835; p = 0.047), and the use of any medication during pregnancy (OR = 2.413; p = 0.03). In logistic regression model, adding GST genotypes did not modify the significant effects found for prematurity and neonatal jaundice as risk factors in ASD. However, there was a significant interaction of GST genotype with medication use during pregnancy and the use of tocolytics during pregnancy, which was predictive of ASD risk only in carriers of GSTM1-null, as opposed to carriers of GSTM1-active genotype. Conclusion: Specific perinatal complications may be significant risk factors for ASD. GSTM1 genotype may serve as a moderator of the effect of some prenatal factors on the risk of ASD such as using medication during pregnancy. It may be speculated that different oxidative stress-related genetic and environmental factors could lead to development of ASD. Apart from etiological mechanisms, possible therapeutic implications in ASD are also discussed.

Maternal immigrant status and signs of neurodevelopmental problems in early childhood: The French representative ELFE birth cohort

A growing body of evidence suggests that children of immigrants may have increased risks of neurodevelopmental disorders. However, evidence based on parent report and on very young children is lacking. We therefore investigated the association between maternal immigrant status and early signs of neurodevelopmental problems in a population-based sample of 2-year-old children using standardized parent-report instruments. We used data from the French representative Étude Longitudinale Française depuis l'Enfance birth cohort, initiated in 2011. The study sample included 9,900 children of nonimmigrant French, 1,403 children of second, and 1,171 children of first generation immigrant women followed-up to age 2 years. Neurodevelopment was assessed using the Modified Checklist for Autism in Toddlers (M-CHAT) and an adaptation of the MacArthur-Bates Communicative Development Inventories (MB-CDI). In fully adjusted linear regression models, maternal immigrant status was associated with M-CHAT scores, with stronger associations in children of first (β-coefficient: 0.19; 95% CI 0.08-0.29) than second generation immigrants (0.09; 0.01-0.17). This association was especially strong among children of first generation immigrant mothers native of North Africa (vs. nonimmigrant French: 0.33; 0.16-0.49) and French-speaking Sub-Saharan Africa (0.26; 0.07-0.45). MB-CDI scores were lowest among children of first generation immigrant mothers, particularly from mostly non-francophone regions. Children of first generation immigrant mothers were most likely to have simultaneously low MB-CDI and high M-CHAT scores. Our findings suggest that maternal immigrant status is associated with early signs of neurodevelopmental difficulties, with strong variations according to maternal region of origin. Further research is necessary to test whether these associations persist and to determine the underlying mechanisms. Autism Res 2019, 12: 1845-1859. © 2019 International Society for Autism Research, Wiley Periodicals, Inc. LAY SUMMARY: We asked immigrant and nonimmigrant mothers in France about early signs of neurodevelopmental problems in their 2-year-old children. Overall, we found that children of immigrants may be at higher risk of showing these early warning signs, as compared to children of nonimmigrants. This is in line with previous studies, which were based on doctors' diagnoses at later ages. However, our results differed depending on the mothers' regions of origin. We found the highest risks in children of first generation immigrants from North and French-speaking Sub-Saharan Africa, who also seemed especially at risk of neurodevelopmental problems combined with low language development.

[Neurodevelopment of children born very preterm with extremely low and very low body weight]

AIM

To evaluate the characteristics of neurodevelopment by the age of 5-8 years in children who were born very preterm with extremely low body weight (ELBW) and very low body weight (VLBW).

MATERIAL AND METHODS

Seventy-two patients, aged from 5 years to 8 years were examined. Patients were divided into group I (36 patients born preterm with ELBW (16 boys, 20 girls)) and group II (36 patients born with VLBW (16 boys, 20 girls)). The control group included 30 healthy peers (16 boys, 14 girls). All children were assessed by means of the Griffiths Mental Development Scales, Extended Revised: 2 to 8 years (GMDS-ER 2-8).

RESULTS

The value of general quotient (GQ) in patients born with ELBW (73.4±2.1) was significantly lower compared to their healthy peers (80.9±2.1; p=0.036). The same tendency was found in patients born with VLBW who's GQ was decreased by 73.1±3.0 (p=0.101). Concurrently the patients demonstrated lower scores on all six scales, which achieved significant difference with the controls for the 'Locomotor' and 'Performance' scales in group I, and for the 'Performance' and 'Practical reasoning' scales in group II. The boys born with ELBW tended to demonstrate lower results on all six scales and received significantly lower scores on the 'Locomotor' and 'Language' scales. The boys born with VLBW demonstrated significantly lower scores on the 'Language', 'Eye and hand co-ordination' and 'Practical reasoning' scales. In girls significantly lower score on the 'Performance' scale only was shown for those, who were born with ELBW.

CONCLUSION

Early diagnosis and characterization of developmental delays in children born very preterm determine the effectiveness of therapeutic measures based on the individual approach and comprehensive medical-psychological-pedagogical support.

Neuroanatomical Correlates of Advanced Paternal and Maternal Age at Birth in Autism Spectrum Disorder

Although advanced paternal and maternal age at birth (PA/MA) increases the risk of autism spectrum disorder (ASD), the underlying neurobiological mechanisms are not fully understood. To explore the neuroanatomical correlates of advanced PA/MA, the current study conducted brain morphometric analyses in 39 high-functioning adult males with ASD and 39 age-, intellectual level-, and parental socioeconomic background-matched, typically developed (TD) males. Whole-brain analysis revealed that the regional gray matter volume (GMV) in bilateral posterior cingulate cortex (PCC) and precuneus (PCU) were significantly smaller in the individuals with ASD than in TD subjects (false discovery rate-corrected P = 0.014). Additional analyses of the constituents of GMV reduction in these brain regions revealed that the cortical thickness of the right ventral PCC was significantly thinner (P = 0.014) and the surface area of bilateral PCU was significantly smaller (left: P = 0.001; right: P = 0.049) in the adults with ASD, compared with TD subjects. Although the analyses were exploratory, the thinner cortical thickness of right ventral PCC was significantly correlated with older PA in the ASD individuals (P = 0.028). The current findings shed new light on the neurobiological mechanisms underlying the link between advanced PA and ASD.

Early Infant Attention as a Predictor of Social and Communicative Behavior in Childhood

Background

The objective was to determine whether infant neurobehavior measured at five post-gestational weeks could predict social and communicative behavior (SCB) through five and eight years.

Methods

Infant neurobehavior was assessed using the Neonatal Intensive Care Unit Network Neurobehavioral Scale, and SCB was measured using the Social Responsiveness Scale (SRS). Adjusted linear regression with generalized estimating equations were employed to estimate the association between infant neurobehavior and SCB. Interaction terms and stratification were used to identify potential effect modification by autism spectrum disorder risk factors.

Results

The analyses include n = 214 and n = 227 participants who were examined at 5 weeks and followed to 4/5 and 8 years, respectively. Adjusting for maternal age, race, parity, and education as well as gestational age, only the Neonatal Intensive Care Unit Network Neurobehavioral Scale summary score of "attention" (measured at mean 43.9 gestational weeks) was inversely associated with total SRS T-score through 5 years. However, in analyses stratified by maternal age, the inverse association between "attention" and SCB was significant, but only among offspring of women of advanced maternal age (≥35 y); in addition, higher scores of "excitability," "lethargy," and "arousal" were associated with increased total SRS T scores among women of advanced maternal age. The associations were no longer statistically significant at 8 years.

Conclusions

Newborns with lower scores on the attention subscale (determined by an ability to localize and track animate and inanimate objects) were more likely to demonstrate deficits in SCB. In addition, infants with increased excitability, lethargy, or increased arousal were more likely to have impaired SCB that persisted through 5 years, but not at 8 years of age. Further work is necessary to identify specific aspects of infant neurobehavior that may affect childhood SCBs.

Relation Between Infant Microbiota and Autism?: Results from a National Cohort Sibling Design Study

BACKGROUND

Hypotheses concerning adverse effects of changes in microbiota have received much recent attention, but unobserved confounding makes them difficult to test. We investigated whether surrogate markers for potential adverse microbiota change in infancy affected autism risk, addressing unobserved confounding using a sibling study design.

METHODS

This is a population-based, prospective cohort study including all singleton live births in Denmark from 1997 to 2010. The exposure variables were cesarean delivery and antibiotic use in the first 2 years of life. The outcome was a subsequent autism diagnosis. We used the between- and within-sibling model and compared it with sibling-stratified Cox models and simpler standard Cox models that ignored sibship.

RESULTS

Of our study population including 671,606 children, who were followed for up to 15 years (7,341,133 person-years), 72% received antibiotics, 17.5% were delivered by cesarean, and 1.2% (8,267) developed autism. The standard Cox models predicted that both cesarean (compared with vaginal) delivery and antibiotics increased the risk of autism. In the sibling-stratified Cox model, only broader spectrum antibiotics were associated with increased risk of autism: hazard ratio (HR) = 1.16 (95% confidence interval = 1.01, 1.36). The between-within model estimated no exposure effects: intrapartum cesarean HR = 1.06 (0.89, 1.26); prelabor cesarean HR = 0.97 (0.83, 1.15); exclusively penicillin HR = 1.05 (0.93, 1.18); and broader spectrum antibiotics HR = 1.05 (0.95, 1.16).

CONCLUSIONS

The between-within model rendered more precise estimates than sibling-stratified Cox models, and we believe that it also provided more valid estimates. Results from these preferred models do not support a causal relation between antibiotic treatment during infancy, cesarean delivery, and autism. See video abstract at, http://links.lww.com/EDE/B432.

Asperger's syndrome: What to consider?

Asperger's syndrome is a neurodevelopmental disorder which is part of the large family of autism spectrum disorders. People with Asperger's syndrome have difficulties in social interactions, verbal and non-verbal communication, and may display behavioural oddities, with stereotypies and limited interests. They show no language delay and their cognitive development is not marked by an overall delay but by specific impairments in certain areas such as the executive functions. The clinical presentations are very heterogeneous, varying according to age and psychiatric comorbidities. Screening, diagnosis and specialized treatment are not made any easier by the diversity of the clinical manifestations. Asperger's syndrome is often diagnosed belatedly, at 11years of age on average and even in adulthood in some cases. This late diagnosis has a significant impact on the risks of depression and a poor quality of life. However, in adulthood or in adolescence, certain situations, personality traits and cognitive profiles or certain comorbidities should suggest the hypothesis of an Asperger-type autism spectrum disorder. We propose here a review of the clinical situations at different ages of life that could help with the screening and the referral of patients to specialized clinicians for diagnosis and appropriate treatment.

Early life exposure to particulate matter air pollution (PM1, PM2.5 and PM10) and autism in Shanghai, China: A case-control study

BACKGROUND

The evidence for adverse effects of ambient particulate matter (PM) pollution on mental health is limited. Studies in Western countries suggested higher risk of autism spectrum disorder (ASD) associated with PM air pollution, but no such study has been done in developing countries.

METHODS

A case-control study was performed in Shanghai with a multi-stage random sampling design. Children's exposures to PM₁, PM_2.5 and PM₁₀ (particulate matter with aerodynamic diameter < 1 μm, < 2.5 μm and < 10 μm, respectively) during the first three years after birth were estimated with satellite remote sensing data. Conditional logistic regression was used to examine the PM-ASD association.

RESULTS

In total, 124 ASD cases and 1240 healthy controls were included in this study. The median levels of PM₁, PM_2.5 and PM₁₀ exposures during the first three years of life were 48.8 μg/m³, 66.2 μg/m³ and 95.4 μg/m³, respectively, and the interquartile range (IQR) for these three pollutants were 4.8 μg/m³, 3.4 μg/m³ and 4.9 μg/m³, respectively. The adjusted odds ratios (and 95% confidence intervals) of ASD associated with an IQR increase for PM₁, PM_2.5 and PM₁₀ were 1.86 (1.09, 3.17), 1.78 (1.14, 2.76) and 1.68 (1.09, 2.59), respectively. Higher ORs of ASD associated with PM pollution were observed in the second and the third year after birth.

CONCLUSIONS

Exposures to PM₁, PM_2.5 and PM₁₀ during the first three years of life were associated with the increased risk of ASD and there appeared to be stronger effects of ambient PM pollution on ASD in the second and the third years after birth.

Does perinatal exposure to exogenous oxytocin influence child behavioural problems and autistic-like behaviours to 20 years of age?

BACKGROUND

The neuropeptide and hormone oxytocin is known to have a significant impact on social cognition and behaviour in humans. There is growing concern regarding the influence of exogenous oxytocin (OT) administration in early life on later social and emotional development, including autism spectrum disorder (ASD). No study has examined offspring development in relation to the dose of exogenous oxytocin administered during labour.

METHODS

Between 1989 and 1992, 2,900 mothers were recruited prior to the 18th week of pregnancy, delivering 2,868 live offspring. The Child Behaviour Checklist was used to measure offspring behavioural difficulties at ages 5, 8, 10, 14 and 17 years. Autism spectrum disorder was formally diagnosed by consensus of a team of specialists. At 20 years, offspring completed a measure of autistic-like traits, the Autism Spectrum Quotient (AQ). Oxytocin exposure prior to birth was analysed using categorical and continuous approaches (maternal oxytocin dose) with univariate and multivariate statistical techniques.

RESULTS

Categorical analyses of oxytocin exposure prior to birth demonstrated no group differences in any measures of child behaviour. A small in magnitude dose-response association was observed for clinically significant total behaviour symptoms (adjusted odds ratio 1.03; 95% CI: 1.01-1.06, p < .01). Exogenous oxytocin administration prior to birth was not associated with ASD (OR: 0.64; 95% CI: 0.15-2.12, p = .46) or high levels of autistic-like traits (p = .93), as assessed by the AQ.

CONCLUSIONS

This study is the first to investigate longitudinal mental health outcomes associated with the use of oxytocin-based medications during labour. The results do not provide evidence to support the theory that exogenous OT has a clinically significant negative impact on the long-term mental health of children.

Moderating effect of mode of delivery on the genetics of intelligence: Explorative genome-wide analyses in ALSPAC

INTRODUCTION

Intelligence is a core construct of individual differences in cognitive abilities and a strong predictor of important life outcomes. Within recent years, rates of cesarean section have substantially increased globally, though little is known about its effect on neurodevelopmental trajectories. Thus, we aimed to investigate the influence of delivery by cesarean section on the genetics of intelligence in children.

METHODS

Participants were recruited through the Avon Longitudinal Study of Parents and Children (ALSPAC). Intelligence was measured by the Wechsler Intelligence Scale for Children (WISC). Genotyping was performed using the Illumina Human Hap 550 quad genome-wide SNP genotyping platform and was followed by imputation using MACH software. Genome-wide interaction analyses were conducted using linear regression.

RESULTS

A total of 2,421 children and 2,141,747 SNPs were subjected to the genome-wide interaction analyses. No variant reached genome-wide significance. The strongest interaction was observed at rs17800861 in the GRIN2A gene (β = -3.43, 95% CI = -4.74 to -2.12, p = 2.98E-07). This variant is predicted to be located within active chromatin compartments in the hippocampus and may influence binding of the NF-kappaB transcription factor.

CONCLUSIONS

Our results may indicate that mode of delivery might have a moderating effect on genetic disposition of intelligence in children. Studies of considerable sizes (>10,000) are likely required to more robustly detect variants governing such interaction. In summary, the presented findings prompt the need for further studies aimed at increasing our understanding of effects various modes of delivery may have on health outcomes in children.

Neurodevelopmental and emotional-behavioral outcomes in late-preterm infants: an observational descriptive case study

BACKGROUND

Over the last decade, several studies investigated the outcomes in children born very preterm. Only recently there has been an increasing interest in the late preterm infants (born between 34 + 0 and 36 + 6 weeks). This population is at high risk of morbidity and mortality in the first years of life. Other studies reported that they are also at risk of long-term developmental problem. Therefore, the aim of this study is to describe the neurodevelopmental and emotional-behavioral outcome in a sample of late preterm patients.

METHODS

The study included late preterm children and adolescents who had neuropsychiatric and/or neurological symptoms. They underwent a general, neurocognitive and an emotional-behavioral assessment. Exclusion criteria included: patients affected by Central Nervous System congenital abnormalities, neurodegenerative diseases, genetic disorders, epilepsy, or in pharmacological treatment, or adopted children. A descriptive statistics analysis was performed to describe the sociodemographic and clinical characteristics of patients. Risk factors related to late preterm birth, prevalence of neurodevelopmental disorders, and cognitive functioning were recorded and analyzed.

RESULTS

The sample included 68 LPI (45 males and 23 females) aged from 2 to 16.3 years (mean age 7,5 years), who were affected by one or more neurodevelopmental disorder, including Language Disorder, Attention Deficit Hyperactivity Disorder, Specific Learning Disorder, Developmental Coordination Disorder, Intellectual Disability and Autism Spectrum Disorder. Moreover, in 30.8% of patients, internalizing problems (affective and social skills problem) were detected.

CONCLUSIONS

Our results support the importance of a long-term surveillance of late preterm and the great need for more longitudinal large population studies in order to collect data on the neurodevelopmental outcomes of this population.

Prenatal, perinatal, and neonatal risk factors of autism spectrum disorder

BACKGROUND

We explored the association of 29 previously reported neonatal, perinatal, and prenatal conditions, and exposures with later diagnosis of autism spectrum disorder (ASD) in a large sample of children followed over multiple years.

METHODS

A retrospective case-cohort study was formed using the Military Health System database. Cases were identified by International Classification of Diseases, Ninth Revision codes for ASD between 2000 and 2013, and were matched 3:1 with controls on sex, date of birth, and enrollment time frame. Exposures included 29 conditions previously associated with ASD; 17 prenatal conditions and their pharmaceutical treatment, 5 perinatal conditions, and 6 neonatal conditions.

RESULTS

A total of 8,760 children diagnosed with ASD between the ages of 2 and 18 years were matched with 26,280 controls. ASD is associated with maternal mental illness, epilepsy, obesity, hypertension, diabetes, polycystic ovary syndrome, infection, asthma, assisted fertility, hyperemesis, younger maternal age, labor complications, low birth weight, infant infection, epilepsy, birth asphyxia, and newborn complications. The greatest increased risk was associated with infant epilepsy (odds ratio (OR) 7.57 (5.68-10.07)), maternal mental health (OR 1.80 (1.65-1.96)), and epilepsy (OR 1.60 (1.02-2.50)) medications.

CONCLUSION

ASD is associated with a range of prenatal, perinatal, and neonatal factors, with the highest magnitude associations with maternal medication use and neonatal seizure.

Prenatal and perinatal risk factors and the clinical implications on autism spectrum disorder

Prenatal and perinatal factors may increase the risk of autism spectrum disorder. However, little is known about whether unaffected siblings of probands with autism spectrum disorder also share the phenomenon and whether the prenatal/perinatal factors are related to the clinical severity of autistic symptoms. We compared the frequency of prenatal and perinatal factors among 323 probands with autism spectrum disorder (mean age ± standard deviation, 10.7 ± 3.5 years; males, 91.0%), 257 unaffected siblings (11.7 ± 4.5; 42.8%), and 1504 typically developing controls (8.9 ± 1.6 years; 53.1%); and investigated their effects on the severity of autistic symptoms. We found that probands with autism spectrum disorder and their unaffected siblings had more prenatal/perinatal events than typically developing controls with higher numbers of prenatal/perinatal factors in probands than in unaffected siblings. The prenatal/perinatal events were associated with greater stereotyped behaviors, social-emotional problems, socio-communication deficits, and overall severity. We also found that six prenatal/perinatal factors (i.e. preeclampsia, polyhydramnios, oligoamnios, placenta previa, umbilical cord knot, and gestational diabetes) were associated with the severity of autistic symptoms, particularly stereotyped behaviors and socio-communication deficits. Our findings suggest that prenatal and perinatal factors may potentially moderate the clinical expression of autism spectrum disorder. The underlying mechanism warrants further research.

Methylation-reprogrammed Wnt/β-catenin signalling mediated prenatal hypoxia-induced brain injury in foetal and offspring rats

Prenatal hypoxia (PH) is a common pregnancy complication, harmful to brain development. This study investigated whether and how PH affected Wnt pathway in the brain. Pregnant rats were exposed to hypoxia (10.5% O₂) or normoxia (21% O₂; Control). Foetal brain weight and body weight were decreased in the PH group, the ratio of brain weight to body weight was increased significantly. Prenatal hypoxia increased mRNA expression of Wnt3a, Wnt7a, Wnt7b and Fzd4, but not Lrp6. Activated β‐catenin protein and Fosl1 expression were also significantly up‐regulated. Increased Hif1a expression was found in the PH group associated with the higher Wnt signalling. Among 5 members of the Sfrp family, Sfrp4 was down‐regulated. In the methylation‐regulating genes, higher mRNA expressions of Dnmt1 and Dnmt3b were found in the PH group. Sodium bisulphite and sequencing revealed hyper‐methylation in the promoter region of Sfrp4 gene in the foetal brain, accounting for its decreased expression and contributing to the activation of the Wnt‐Catenin signalling. The study of PC12 cells treated with 5‐aza further approved that decreased methylation could result in the higher Sfrp4 expression. In the offspring hippocampus, protein levels of Hif1a and mRNA expression of Sfrp4 were unchanged, whereas Wnt signal pathway was inhibited. The data demonstrated that PH activated the Wnt pathway in the foetal brain, related to the hyper‐methylation of Sfrp4 as well as Hif1a signalling. Activated Wnt signalling might play acute protective roles to the foetal brain in response to hypoxia, also would result in disadvantageous influence on the offspring in long‐term.

Current Enlightenment About Etiology and Pharmacological Treatment of Autism Spectrum Disorder

Autistic Spectrum Disorder (ASD) is a complex neurodevelopmental brain disorder characterized by two core behavioral symptoms, namely impairments in social communication and restricted/repetitive behavior. The molecular mechanisms underlying ASD are not well understood. Recent genetic as well as non-genetic animal models contributed significantly in understanding the pathophysiology of ASD, as they establish autism-like behavior in mice and rats. Among the genetic causes, several chromosomal mutations including duplications or deletions could be possible causative factors of ASD. In addition, the biochemical basis suggests that several brain neurotransmitters, e.g., dopamine (DA), serotonin (5-HT), gamma-amino butyric acid (GABA), acetylcholine (ACh), glutamate (Glu) and histamine (HA) participate in the onset and progression of ASD. Despite of convincible understanding, risperidone and aripiprazole are the only two drugs available clinically for improving behavioral symptoms of ASD following approval by Food and Drug Administration (FDA). Till date, up to our knowledge there is no other drug approved for clinical usage specifically for ASD symptoms. However, many novel drug candidates and classes of compounds are underway for ASD at different phases of preclinical and clinical drug development. In this review, the diversity of numerous aetiological factors and the alterations in variety of neurotransmitter generation, release and function linked to ASD are discussed with focus on drugs currently used to manage neuropsychiatric symptoms related to ASD. The review also highlights the clinical development of drugs with emphasis on their pharmacological targets aiming at improving core symptoms in ASD.

Invited Commentary: Male Reproductive System Congenital Malformations and the Risk of Autism Spectrum Disorder

Autism spectrum disorder (ASD) is a prevalent developmental disorder. Studies indicate that while ASD etiology has a genetic component, the risk is polygenic, with gene-environment interactions being likely. The prenatal period is a critical exposure window for nongenetic risk factors. Previous studies have found positive associations between congenital malformations (all types) and ASD; a few also found specific associations between genitourinary system malformations and ASD; and one study found an association between hypospadias and ASD. In the accompanying article, Rotem et al. (Am J Epidemiol. 2018;187(4):656-663) describe how they conducted a comprehensive analysis focusing on the shared risk of ASD with hypospadias or cryptorchidism, using existing data from a large Israeli health services system, which afforded several advantages because of the large sample size and low attrition of the patient population. The authors conducted a careful analysis, including sensitivity analyses, to account for risk factor and case misclassifications that might have occurred had they relied solely on preexisting diagnostic codes to define exposures and outcome. They observed positive associations between both hypospadias and cryptorchidism and ASD that were independent of numerous sociodemographic and pregnancy health factors. This study advances our understanding of ASD etiology and illustrates how existing data might be used to assess some ASD risk factors.

The early development of infant siblings of children with autism spectrum disorder: Characteristics of sibling interactions

Although sibling interactions play an important role in children's early development, they are rarely studied in very young children with an older brother or sister with autism spectrum disorder (ASD). This study used a naturalistic, observational method to compare interactions between 18-month-old infants and their older sibling with ASD (n = 22) with a control group of 18-month-old infants and their typically developing (TD) older sibling (n = 29). In addition, role (a)symmetry and the influence of gender were evaluated. Sibling interactions in ASD-dyads were characterized by higher levels of negativity. Although somewhat less pronounced in ASD-dyads, role asymmetry was present in both groups, with the older child taking the dominant position. Finally, siblings pairs with an older sister were characterized by more positive behaviours. Since differences in sibling interactions may alter the developmental trajectories of both siblings, these early relationships should be taken into account in future ASD research and interventions.

Infant Health and Future Childhood Adversity

Objective To investigate the extent to which disabling infant health conditions are associated with adverse childhood experiences at age 5. Methods We conducted a secondary analysis of data from the Fragile Families and Child Wellbeing Study, a national urban birth cohort. We estimated logistic regression models of associations between the presence of a disabling infant health condition and the child's ACE exposures at age 5, controlling for factors that preceded the child's birth, including the mother's sociodemographic characteristics, physical health, mental illness, and substance abuse and the parents' criminal justice system involvement and domestic violence or sexual abuse. ACEs included 4 categories of child maltreatment (physical, sexual, psychological abuse, neglect) and 5 categories of household dysfunction (father absence, substance use, mental illness, caregiver treated violently, incarceration). Results 3.3% of the children were characterized as having a disabling health condition that was likely present at birth. Logistic regression estimates indicate that having a disabling infant health condition was associated with 83% higher odds of the child experiencing 2 or more ACEs (AOR 1.83, CI 1.14-2.94) and 73% higher odds of the child experiencing 3 or more ACEs (AOR 1.73, CI 1.07-2.77) at age 5. Conclusions for Practice The finding of strong links between disabling infant health conditions and ACEs at age 5 suggests that child health and ACEs play intertwining and mutually reinforcing roles during the early lifecourse and highlights the critical importance of investing in systems that simultaneously promote optimal child development and address childhood adversity.

Maternal body mass index before pregnancy as a risk factor for ADHD and autism in children

The risk of attention-deficit/hyperactivity disorder (ADHD) and autism spectrum disorders (ASD) may be influenced by environmental factors such as maternal obesity before pregnancy. Previous studies investigating those associations have found divergent results. We aim to investigate in a large birth cohort this association further in children with ADHD, ASD and comorbid ADHD and ASD. Our study population consisted of 81,892 mother-child pairs participating in the Danish National Birth Cohort (DNBC). Information about pre-pregnancy weight and height was collected in week 16 of pregnancy; the analysis was divided into groups based on BMI. Children with a clinical diagnosis of ADHD and/or ASD were identified in the Danish health registries at an average age of 13.3 years. Hazard ratios (HRs) were estimated using time-to-event analysis. Compared to normal weight mothers, the risk of having a child with ADHD was significantly increased if the mother was overweight (HR = 1.28 [95% CI 1.15;1.48]), obese (HR = 1.47 [95% CI 1.26;1.71]) or severely obese (HR = 1.95 [95% CI 1.58;2.40]). The same pattern was seen for the combined ADHD and ASD group. Regarding ASD, an increased risk was observed in underweight (HR = 1.30 [95% CI 1.01;1.69]) and obese (HR = 1.39 [95% CI 1.11;1.75]) mothers. Subgroup analysis revealed that the association in the ADHD group could mostly be attributable to the hyperactive group. Maternal obesity before pregnancy is a risk factor for ADHD in children. Maternal obesity as well as underweight may also be associated with an increased risk for ASD.

Maternal Diabetes and Fetal Programming Toward Neurological Diseases: Beyond Neural Tube Defects

The purpose of this review was to search for experimental or clinical evidence on the effect of hyperglycemia in fetal programming to neurological diseases, excluding evident neural tube defects. The lack of timely diagnosis and the inadequate control of diabetes during pregnancy have been related with postnatal obesity, low intellectual and verbal coefficients, language and motor deficits, attention deficit with hyperactivity, problems in psychosocial development, and an increased predisposition to autism and schizophrenia. It has been proposed that several childhood or adulthood diseases have their origin during fetal development through a phenomenon called fetal programming. However, not all the relationships between the outcomes mentioned above and diabetes during gestation are clear, well-studied, or have been related to fetal programming. To understand this relationship, it is imperative to understand how developmental processes take place in health, in order to understand how the functional cytoarchitecture of the central nervous system takes place; to identify changes prompted by hyperglycemia, and to correlate them with the above postnatal impaired functions. Although changes in the establishment of patterns during central nervous system fetal development are related to a wide variety of neurological pathologies, the mechanism by which several maternal conditions promote fetal alterations that contribute to impaired neural development with postnatal consequences are not clear. Animal models have been extremely useful in studying the effect of maternal pathologies on embryo and fetal development, since obtaining central nervous system tissue in humans with normal appearance during fetal development is an important limitation. This review explores the state of the art on this topic, to help establish the way forward in the study of fetal programming under hyperglycemia and its impact on neurological and psychiatric disorders.

Epigenetics of Autism Spectrum Disorder

Autism spectrum disorder (ASD), one of the most common childhood neurodevelopmental disorders (NDDs), is diagnosed in 1 of every 68 children. ASD is incredibly heterogeneous both clinically and aetiologically. The etiopathogenesis of ASD is known to be complex, including genetic, environmental and epigenetic factors. Normal epigenetic marks modifiable by both genetics and environmental exposures can result in epigenetic alterations that disrupt the regulation of gene expression, negatively impacting biological pathways important for brain development. In this chapter we aim to summarize some of the important literature that supports a role for epigenetics in the underlying molecular mechanism of ASD. We provide evidence from work in genetics, from environmental exposures and finally from more recent studies aimed at directly determining ASD-specific epigenetic patterns, focusing mainly on DNA methylation (DNAm). Finally, we briefly discuss some of the implications of current research on potential epigenetic targets for therapeutics and novel avenues for future work.

Neonatal and regressive forms of autism: Diseases with similar symptoms but a different etiology

Autistic Spectrum Disorder (ASD) can be a debilitating, life-long neurocognitive disease. ASD is caused by genetic and epigenetic factors and largely unknown and poorly understood environmental triggers. Signs and symptoms of ASD often appear in the first year of life while the disease strikes other infants who had previously been developing normally at around 2years of age. Ozonoff and her colleagues recently suggested that there are three different pathways or trajectories for the development of ASD in infants 6-24months of age. I hypothesize that pathway 1 is caused by in utero insult/injury, pathway 2 by obstetric complications at birth, and pathway 3 by environmental triggers of ASD affecting infants 0-3years of age. Faster progress can be made in elucidating the underlying causes of neonatal and regressive forms of ASD if the diseases are investigated separately, instead of being part of the same disorder.

Impaired Redox Control in Autism Spectrum Disorders: Could It Be the X in GxE?

PURPOSE OF REVIEW

This review aims to provide a brief description of the complex etiology of autism spectrum disorders (ASD), with special emphasis on the recent findings of impaired redox control in ASD, and to suggest a possible model of oxidative stress-specific gene-environment interaction in this group of disorders.

RECENT FINDINGS

Recent findings point out to the significance of environmental, prenatal, and perinatal factors in ASD but, at the same time, are in favor of the potentially significant oxidative stress-specific gene-environment interaction in ASD. Available evidence suggests an association between both the identified environmental factors and genetic susceptibility related to the increased risk of ASD and the oxidative stress pathway. There might be a potentially significant specific gene-environment interaction in ASD, which is associated with oxidative stress. Revealing novel susceptibility genes (including those encoding for antioxidant enzymes), or environmental factors that might increase susceptibility to ASD in carriers of a specific genotype, might enable the stratification of individuals more prone to developing ASD and, eventually, the possibility of applying preventive therapeutic actions.

The association between placental histopathology and autism spectrum disorder

INTRODUCTION

Research suggests that autism spectrum disorder (ASD) has its origins in utero. This study examines the association between evidence of placental histopathology and ASD.

METHODS

Administrative claims data and medical records data were used to identify ASD cases (N = 55) and matched controls (N = 199) born at New York Methodist Hospital between 2007 and 2014 and subsequently seen in affiliated pediatrics clinics. Placentas from all births during this time period were reviewed as part of routine care. Data were analyzed using conditional logistic regression to account for the matched (gender, gestational age, and birth weight) design.

RESULTS

Acute placental inflammation, regardless of type was associated with an increased risk of ASD (odds ratio [OR] = 3.14, 95% CI = 1.39, 6.95). Chronic uteroplacental vasculitis (OR = 7.13; 95% CI = 1.17, 43.38), the fetal inflammatory response in the chorionic plate vessels (OR = 5.12; 95% CI = 2.02, 12.96), and maternal vascular malperfusion pathology (OR = 12.29; 95% CI = 1.37, 110.69) were associated with an increased risk of ASD. Placental villous edema was associated with a decreased risk of ASD (OR = 0.05; 95% CI = 0.0005, 0.42). In subanalyses among male placentas acute inflammation overall, fetal inflammatory response in the chorionic plate vessels, and maternal vascular malperfusion pathology remained significantly associated with an increased risk of ASD whereas placental villous edema remained associated with a decreased risk of ASD.

DISCUSSION

Histologic evidence of placental inflammation and maternal vascular malperfusion pathology are associated with ASD.

CARACTERÍSTICAS PERINATAIS DE CRIANÇAS COM TRANSTORNO DO ESPECTRO AUTISTA

Objective:

To analyze perinatal features of children with autism spectrum disorder (ASD).

Methods:

Retrospective review of the medical records of 75 children with ASD, between January 2008 and January 2015. Inclusion criteria were diagnosis of ASD based on DSM-5 criteria, and the informed consent form signed by the person who is legally responsible. The exclusion criterion was missing on the medical record. The variables analyzed were maternal age, prematurity (gestational age under 37 weeks), low birth weight (<2,500 g), and perinatal asphyxia (5^th minute Apgar score <7). Data were analyzed using the difference between proportions test, being significant p<0.05.

Results:

Seventy-five patients were included. Maternal age ranged from 21.4 to 38.6 years (29.8±4.1 years). Premature birth occurred in 14 (18.7%) patients, perinatal asphyxia in 6 (8.0%), and low birth weight in 32 (42.6%) patients. The prevalence of prematurity, low birth weight, and perinatal asphyxia among the children in our study was higher than the general prevalence of these conditions among all live births in our country, region, and state, which are, respectively, 11.5, 2.3, and 8.5% in Brazil; 11.0, 2.2, and 8.5% in Southern Brazil; and 10.5, 2.0, and 8.4% in the state of Paraná.

Conclusions:

Our findings show a higher prevalence of prematurity, low birth weight, and perinatal asphyxia among children with ASD. Some limitations are the retrospective study design, and the small sample size. Large prospective studies are needed to clarify the possible association between perinatal complications and ASD.

Developmental microglial priming in postmortem autism spectrum disorder temporal cortex

Microglia can shift into different complex morphologies depending on the microenvironment of the central nervous system (CNS). The distinct morphologies correlate with specific functions and can indicate the pathophysiological state of the CNS. Previous postmortem studies of autism spectrum disorder (ASD) showed neuroinflammation in ASD indicated by increased microglial density. These changes in the microglia density can be accompanied by changes in microglia phenotype but the individual contribution of different microglia phenotypes to the pathophysiology of ASD remains unclear. Here, we used an unbiased stereological approach to quantify six structurally and functionally distinct microglia phenotypes in postmortem human temporal cortex, which were immuno-stained with Iba1. The total density of all microglia phenotypes did not differ between ASD donors and typically developing individual donors. However, there was a significant decrease in ramified microglia in both gray matter and white matter of ASD, and a significant increase in primed microglia in gray matter of ASD compared to typically developing individuals. This increase in primed microglia showed a positive correlation with donor age in both gray matter and white of ASD, but not in typically developing individuals. Our results provide evidence of a shift in microglial phenotype that may indicate impaired synaptic plasticity and a chronic vulnerability to exaggerated immune responses.

Prenatal, perinatal, and postnatal factors associated with autism: A meta-analysis

BACKGROUND

The aim of this meta-analysis was to investigate the prenatal, perinatal, and postnatal risk factors for children autism.

METHODS

PubMed, Embase, Web of Science were used to search for studies that examined the prenatal, perinatal, and postnatal risk factors for children autism. A fixed-effects model or random-effects model was used to pool the overall effect estimates.

RESULTS

Data from 37,634 autistic children and 12,081,416 nonautistic children enrolled in 17 studies were collated. During the prenatal period, the factors associated with autism risk were maternal and paternal age≥35 years, mother's and father's race: White and Asian, gestational hypertension, gestational diabetes, maternal and paternal education college graduate+, threatened abortion, and antepartum hemorrhage. During perinatal period, the factors associated with autism risk were caesarian delivery, gestational age≤36 weeks, parity≥4, spontaneous labor, induced labor, no labor, breech presentation, preeclampsia, and fetal distress. During the postnatal period, the factors associated with autism risk were low birth weight, postpartum hemorrhage, male gender, and brain anomaly. Parity≥4 and female were associated with a decreased risk of autism. In addition, exposure to cigarette smoking, urinary infection, mother's and father's race: Black and Hispanic, mother's country of birth outside Europe and North America, umbilical cord around neck, premature membrane rupture, 5-minutes Apgar score<7, and respiratory infection were not associated with increased risk of autism.

CONCLUSION

The present meta-analysis confirmed the relation between some prenatal, perinatal, and postnatal factors with autism. All these factors were examined individually, thus it was still unclear that whether these factors are causal or play a secondary role in the development of autism. Further studies are needed to verify our findings, and investigate the effects of multiple factors on autism, rather than the single factor.

The Changing Epidemiology of Autism Spectrum Disorders

Autism spectrum disorder (ASD) is a complex neurodevelopmental condition with lifelong impacts. Genetic and environmental factors contribute to ASD etiology, which remains incompletely understood. Research on ASD epidemiology has made significant advances in the past decade. Current prevalence is estimated to be at least 1.5% in developed countries, with recent increases primarily among those without comorbid intellectual disability. Genetic studies have identified a number of rare de novo mutations and gained footing in the areas of polygenic risk, epigenetics, and gene-by-environment interaction. Epidemiologic investigations focused on nongenetic factors have established advanced parental age and preterm birth as ASD risk factors, indicated that prenatal exposure to air pollution and short interpregnancy interval are potential risk factors, and suggested the need for further exploration of certain prenatal nutrients, metabolic conditions, and exposure to endocrine-disrupting chemicals. We discuss future challenges and goals for ASD epidemiology as well as public health implications.

Role of Genetics in the Etiology of Autistic Spectrum Disorder: Towards a Hierarchical Diagnostic Strategy

Progress in epidemiological, molecular and clinical genetics with the development of new techniques has improved knowledge on genetic syndromes associated with autism spectrum disorder (ASD). The objective of this article is to show the diversity of genetic disorders associated with ASD (based on an extensive review of single-gene disorders, copy number variants, and other chromosomal disorders), and consequently to propose a hierarchical diagnostic strategy with a stepwise evaluation, helping general practitioners/pediatricians and child psychiatrists to collaborate with geneticists and neuropediatricians, in order to search for genetic disorders associated with ASD. The first step is a clinical investigation involving: (i) a child psychiatric and psychological evaluation confirming autism diagnosis from different observational sources and assessing autism severity; (ii) a neuropediatric evaluation examining neurological symptoms and developmental milestones; and (iii) a genetic evaluation searching for dysmorphic features and malformations. The second step involves laboratory and if necessary neuroimaging and EEG studies oriented by clinical results based on clinical genetic and neuropediatric examinations. The identification of genetic disorders associated with ASD has practical implications for diagnostic strategies, early detection or prevention of co-morbidity, specific treatment and follow up, and genetic counseling.

Extremely low gestational age and very low birthweight for gestational age are risk factors for autism spectrum disorder in a large cohort study of 10-year-old children born at 23-27 weeks' gestation

BACKGROUND

No prospective cohort study of high-risk children has used rigorous exposure assessment and optimal diagnostic procedures to examine the perinatal antecedents of autism spectrum disorder separately among those with and without cognitive impairment.

OBJECTIVE

We sought to identify perinatal factors associated with increased risk for autism spectrum disorder with and without intellectual disability (intelligence quotient <70) in children born extremely preterm.

STUDY DESIGN

This prospective multicenter (14 institutions in 5 states) birth cohort study included children born at 23-27 weeks' gestation in 2002 through 2004 who were evaluated for autism spectrum disorder and intellectual disability at age 10 years. Pregnancy information was obtained from medical records and by structured maternal interview. Cervical-vaginal "infection" refers to maternal report of bacterial infection (n = 4), bacterial vaginosis (n = 30), yeast infection (n = 62), mixed infection (n = 4), or other/unspecified infection (n = 43; eg, chlamydia, trichomonas, or herpes). We do not know the extent to which infection per se was confirmed by microbial colonization. We use the terms "fetal growth restriction" and "small for gestational age" interchangeably in light of the ongoing challenge to discern pathologically from constitutionally small newborns. Severe fetal growth restriction was defined as a birthweight Z-score for gestational age at delivery <-2 (ie, ≥2 SD below the median birthweight in a referent sample that excluded pregnancies delivered for preeclampsia or fetal indications). Participants were classified into 4 groups based on whether or not they met rigorous diagnostic criteria for autism spectrum disorder and intellectual disability (autism spectrum disorder+/intellectual disability-, autism spectrum disorder+/intellectual disability+, autism spectrum disorder-/intellectual disability+, and autism spectrum disorder-/intellectual disability-). Temporally ordered multinomial logistic regression models were used to examine the information conveyed by perinatal factors about increased risk for autism spectrum disorder and/or intellectual disability (autism spectrum disorder+/intellectual disability-, autism spectrum disorder+/intellectual disability+, and autism spectrum disorder-/intellectual disability+).

RESULTS

In all, 889 of 966 (92%) children recruited were assessed at age 10 years, of whom 857 (96%) were assessed for autism spectrum disorder; of these, 840 (98%) children were assessed for intellectual disability. Autism spectrum disorder+/intellectual disability- was diagnosed in 3.2% (27/840), autism spectrum disorder+/intellectual disability+ in 3.8% (32/840), and autism spectrum disorder-/intellectual disability+ in 8.5% (71/840). Maternal report of presumed cervical-vaginal infection during pregnancy was associated with increased risk of autism spectrum disorder+/intellectual disability+ (odds ratio, 2.7; 95% confidence interval, 1.2-6.4). The lowest gestational age category (23-24 weeks) was associated with increased risk of autism spectrum disorder+/intellectual disability+ (odds ratio, 2.9; 95% confidence interval, 1.3-6.6) and autism spectrum disorder+/intellectual disability- (odds ratio, 4.4; 95% confidence interval, 1.7-11). Severe fetal growth restriction was strongly associated with increased risk for autism spectrum disorder+/intellectual disability- (odds ratio, 9.9; 95% confidence interval, 3.3-30), whereas peripartum maternal fever was uniquely associated with increased risk of autism spectrum disorder-/intellectual disability+ (odds ratio, 2.9; 95% confidence interval, 1.2-6.7).

CONCLUSION

Our study confirms that low gestational age is associated with increased risk for autism spectrum disorder irrespective of intellectual ability, whereas severe fetal growth restriction is strongly associated with autism spectrum disorder without intellectual disability. Maternal report of cervical-vaginal infection is associated with increased risk of autism spectrum disorder with intellectual disability, and peripartum maternal fever is associated with increased risk for intellectual disability without autism spectrum disorder.

Environmental factors influencing the risk of autism

Autism is a developmental disability with age of onset in childhood (under 3 years old), which is characterized by definite impairments in social interactions, abnormalities in speech, and stereotyped pattern of behaviors. Due to the progress of autism in recent decades, a wide range of studies have been done to identify the etiological factors of autism. It has been found that genetic and environmental factors are both involved in autism pathogenesis. Hence, in this review article, a set of environmental factors involved in the occurrence of autism has been collected, and finally, some practical recommendations for reduction of the risk of this devastating disease in children are represented.

Meconium exposure and autism risk

OBJECTIVE

This study aims to determine whether fetal meconium passage is associated with autism.

STUDY DESIGN

This retrospective birth cohort analysis of 9 945 896 children born in California 1991 to 2008 linked discharge diagnosis and procedure codes for prenatal stressors, meconium-stained amniotic fluid (MSAF) and meconium aspiration syndrome (MAS) with autism diagnoses for 47 277 children through 2012. We assessed the relative risk of autism by meconium status using logistic regression, adjusting for demographic and clinical features.

RESULTS

Children exposed to meconium (MSAF and MAS) were more likely to be diagnosed with autism in comparison with unexposed children (0.60% and 0.52%, vs 0.47%, respectively). In adjusted analyses, there was a small increase in autism risk associated with MSAF exposure (adjusted relative risk (aRR) 1.18, 95% confidence interval (CI) 1.12 to 1.25), and a marginal association that failed to achieve significance between MAS and autism (aRR 1.08, 95% CI 0.98 to 1.20).

CONCLUSION

Resuscitation of neonates with respiratory compromise from in utero meconium exposure may mitigate long-term neurodevelopmental damage.

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.

Reframing autism as a behavioral syndrome and not a specific mental disorder: Implications of genetic and phenotypic heterogeneity

Clinical and molecular genetics have advanced current knowledge on genetic disorders associated with autism. A review of diverse genetic disorders associated with autism is presented and for the first time discussed extensively with regard to possible common underlying mechanisms leading to a similar cognitive-behavioral phenotype of autism. The possible role of interactions between genetic and environmental factors, including epigenetic mechanisms, is in particular examined. Finally, the pertinence of distinguishing non-syndromic autism (isolated autism) from syndromic autism (autism associated with genetic disorders) will be reconsidered. Given the high genetic and etiological heterogeneity of autism, autism can be viewed as a behavioral syndrome related to known genetic disorders (syndromic autism) or currently unknown disorders (apparent non-syndromic autism), rather than a specific categorical mental disorder. It highlights the need to study autism phenotype and developmental trajectory through a multidimensional, non-categorical approach with multivariate analyses within autism spectrum disorder but also across mental disorders, and to conduct systematically clinical genetic examination searching for genetic disorders in all individuals (children but also adults) with autism.

Prenatal, perinatal and postnatal factors associated with autism spectrum disorder

OBJECTIVE

To identify prenatal, perinatal and postnatal risk factors in children with autism spectrum disorder (ASD) by comparing them to their siblings without autistic disorders.

METHOD

The present study is cross sectional and comparative. It was conducted over a period of three months (July-September 2014). It included 101 children: 50 ASD's children diagnosed according to DSM-5 criteria and 51 unaffected siblings. The severity of ASD was assessed by the CARS.

RESULTS

Our study revealed a higher prevalence of prenatal, perinatal and postnatal factors in children with ASD in comparison with unaffected siblings. It showed also a significant association between perinatal and postnatal factors and ASD (respectively p=0.03 and p=0.042). In this group, perinatal factors were mainly as type of suffering acute fetal (26% of cases), long duration of delivery and prematurity (18% of cases for each factor), while postnatal factors were represented principally by respiratory infections (24%). As for parental factors, no correlation was found between advanced age of parents at the moment of the conception and ASD. Likewise, no correlation was observed between the severity of ASD and different factors. After logistic regression, the risk factors retained for autism in the final model were: male gender, prenatal urinary tract infection, acute fetal distress, difficult labor and respiratory infection.

CONCLUSIONS

The present survey confirms the high prevalence of prenatal, perinatal and postnatal factors in children with ASD and suggests the intervention of some of these factors (acute fetal distress and difficult labor, among others), as determinant variables for the genesis of ASD.

The role of phthalate esters in autism development: A systematic review

BACKGROUND

Available evidence implicates environmental factors in the pathogenesis of autism spectrum disorders (ASD). However, the role of specific environmental chemicals such as phthalate esters that influence ASD risk remains elusive. This paper systematically reviews published evidences on association between prenatal and/or childhood exposure to phthalate and ASD.

METHODS

Studies pertaining to systematic literature search from Scopus, PubMed, PsycInfo and Web of Science prior to December 2015 were identified. The authors included studies which assessed the effect of exposure to phthalates on occurrence of ASD. This comprehensive bibliographic search identified five independent studies. Each eligible paper was summarized with respect to its methods and results with particular attention to study design and exposure assessment. Because of the heterogeneity in the type of included studies, different methods of assessing exposure to phthalates and the use of different statistics for summarizing the results, meta-analysis could not be used to combine the results of included studies.

RESULTS

The results of this systematic review have revealed the limited number of studies conducted and assessed phthalate exposure. Seven studies were regarded as relevant to the objectives of this review. Two of them did not measure phthalate exposure directly and did not result in quantitative results. Out of the five studies in which phthalate exposure was mainly measured by the examining biomarkers in biological samples, two were cohort studies (one with positive results and another one with not clear association). Among the three case control studies, two of them showed a significant relation between exposure to phthalate and ASD and the last case control study had negative results. Indeed, this case control studies showed a compromised phthalate metabolite glucuronidation pathway, as a probable explanation of mechanism of the relation between phthalate exposure and ASD.

CONCLUSIONS

This review reveals evidence showing a connection between exposure to phthalates and ASD. Nevertheless, further research is needed with appropriate attention to exposure assessment and relevant pre and post-natal cofounders.

Maternal infection during pregnancy and risk of autism spectrum disorders: A systematic review and meta-analysis

Conflicting evidence exists with regard to the relationship between maternal infection during pregnancy and the risk of autism spectrum disorder (ASD) in offspring. The aim of this meta-analysis was to systematically assess this relationship. To identify relevant studies, we conducted systematic searches in PubMed and Embase of scientific articles published through March 2016. Random-effects models were adopted to estimate overall relative risk. A total of 15 studies (2 cohort and 13 case-control studies) involving more than 40,000 ASD cases were included in our meta-analysis. Our results showed that maternal infection during pregnancy was associated with an increased risk of ASD in offspring (OR=1.13, 95% confidence interval (CI): 1.03-1.23), particularly among those requiring hospitalization (OR=1.30, 95% CI: 1.14-1.50). Subgroup analyses suggested that risk may be modulated by the type of infectious agent, time of infectious exposure, and site of infection. These findings indicate that maternal infection during pregnancy increases the risk of ASD in offspring. Possible mechanisms may include direct effects of pathogens and, more indirectly, the effects of inflammatory responses on the developing brain.

Risk of Autism Associated With Hyperbilirubinemia and Phototherapy

OBJECTIVE

Whether neonatal hyperbilirubinemia and/or phototherapy increase the risk of autism spectrum disorder (ASD) is unclear. We sought to quantify the risk of ASD associated with elevated total serum bilirubin (TSB) levels and with phototherapy.

METHODS

In a retrospective cohort study of 525 409 infants born at ≥35 weeks' gestation in 15 Kaiser Permanente Northern California (KPNC) hospitals, 1995-2011, we obtained all TSB levels and determined which infants received phototherapy. From the KPNC Autism Registry, we identified patients with ASD diagnosed at a KPNC Autism Center, by a clinical specialist, or by a pediatrician. We calculated Cox proportional hazard ratios (HRs) for time to diagnosis of ASD, adjusting for confounding factors.

RESULTS

Among infants in the birth cohort, 2% had at least 1 TSB level ≥20 mg/dL, and 8% received phototherapy. The rate of ASD was 13 per 1000 births. Crude analyses revealed an association between TSB ≥20 and ASD (relative risk: 1.4; 95% confidence interval [CI]: 1.1-1.6), and between phototherapy and ASD (relative risk: 1.7; 95% CI: 1.5-1.8). After adjusting for confounders, TSB ≥20 (HR: 1.09; 95% CI: 0.89-1.35) and phototherapy (HR: 1.10; 95% CI: 0.98-1.24) were no longer significantly associated with ASD. Independent risk factors for ASD included maternal and paternal age; maternal and paternal higher education; male sex; birth weight <2500 g or ≥4200 g; and later year of birth.

CONCLUSIONS

After adjustment for the effects of sociodemographic factors and birth weight, neither hyperbilirubinemia nor phototherapy was an independent risk factor for ASD.

Maternal Infection During Pregnancy and Autism Spectrum Disorders

We conducted a nested case-control study including 407 cases and 2,075 frequency matched controls to investigate the association between maternal infections during pregnancy and risk of autism spectrum disorders (ASD). Cases, controls, and maternal infections were ascertained from Kaiser Permanente Northern California clinical databases. No overall association between diagnoses of any maternal infection during pregnancy and ASD was observed [adjusted odds ratio (ORadj) = 1.15, 95 % confidence interval (CI) 0.92-1.43]. However, women with infections diagnosed during a hospital admission (ORadj = 1.48, 95 % CI 1.07-2.04), particularly bacterial infections (ORadj = 1.58, 95 % CI 1.06-2.37), were at increased risk of delivering a child with ASD. Multiple infections during pregnancy were associated with ASD (ORadj = 1.36, 95 % CI 1.05-1.78).

Autism spectrum disorder in adults: diagnosis, management, and health services development

Autism spectrum disorder (ASD) is a common neurodevelopmental disorder characterized by pervasive difficulties since early childhood across reciprocal social communication and restricted, repetitive interests and behaviors. Although early ASD research focused primarily on children, there is increasing recognition that ASD is a lifelong neurodevelopmental disorder. However, although health and education services for children with ASD are relatively well established, service provision for adults with ASD is in its infancy. There is a lack of health services research for adults with ASD, including identification of comorbid health difficulties, rigorous treatment trials (pharmacological and psychological), development of new pharmacotherapies, investigation of transition and aging across the lifespan, and consideration of sex differences and the views of people with ASD. This article reviews available evidence regarding the etiology, legislation, diagnosis, management, and service provision for adults with ASD and considers what is needed to support adults with ASD as they age. We conclude that health services research for adults with ASD is urgently warranted. In particular, research is required to better understand the needs of adults with ASD, including health, aging, service development, transition, treatment options across the lifespan, sex, and the views of people with ASD. Additionally, the outcomes of recent international legislative efforts to raise awareness of ASD and service provision for adults with ASD are to be determined. Future research is required to identify high-quality, evidence-based, and cost-effective models of care. Furthermore, future health services research is also required at the beginning and end of adulthood, including improved transition from youth to adult health care and increased understanding of aging and health in older adults with ASD.

Genetic Syndromes, Maternal Diseases and Antenatal Factors Associated with Autism Spectrum Disorders (ASD)

Autism spectrum disorder (ASD) affecting about 1% of all children is associated, in addition to complex genetic factors, with a variety of prenatal, perinatal, and postnatal etiologies. In addition, ASD is often an important clinical presentation of some well-known genetic syndromes in human. We discuss these syndromes as well as the role of the more important prenatal factors affecting the fetus throughout pregnancy which may also be associated with ASD. Among the genetic disorders we find Fragile X, Rett syndrome, tuberous sclerosis, Timothy syndrome, Phelan-McDermid syndrome, Hamartoma tumor syndrome, Prader-Willi and Angelman syndromes, and a few others. Among the maternal diseases in pregnancy associated with ASD are diabetes mellitus (PGDM and/or GDM), some maternal autoimmune diseases like antiphospholipid syndrome (APLS) with anti-β2GP1 IgG antibodies and thyroid disease with anti-thyroid peroxidase (TPO) antibodies, preeclampsia and some other autoimmune diseases with IgG antibodies that might affect fetal brain development. Other related factors are maternal infections (rubella and CMV with fetal brain injuries, and possibly Influenza with fever), prolonged fever and maternal inflammation, especially with changes in a variety of inflammatory cytokines and antibodies that cross the placenta and affect the fetal brain. Among the drugs are valproic acid, thalidomide, misoprostol, and possibly SSRIs. β2-adrenergic receptor agonists and paracetamol have also lately been associated with increased rate of ASD but the data is too preliminary and inconclusive. Associations were also described with ethanol, cocaine, and possibly heavy metals, heavy smoking, and folic acid deficiency. Recent studies show that heavy exposure to pesticides and air pollution, especially particulate matter < 2.5 and 10 μm in diameter (PM2.5 and PM10) during pregnancy is also associated with ASD. Finally, we have to remember that many of the associations mentioned in this review are only partially proven, and not all are "clean" of different confounding factors. The associations described in this review emphasize again how little we know about the etiology and pathogenesis of ASD. It is obvious that we need more epidemiologic data to establish many of these associations, but if proven, they might be promising avenues for prevention.