Birth seasonality and risk of autism spectrum disorder.

Season of birth has been hypothesized to be a risk factor for autism spectrum disorder (ASD). However, the evidence has been mixed and limited due to methodological challenges. We examine ASD birth trends for 5,464,628 births across 5 countries. ASD birth prevalence data were obtained from the International Collaboration for Autism Registry Epidemiology database, including children born in Denmark, Finland, Norway, Sweden, and Western Australia. Empirical mode decomposition and cosinor modeling were used to assess seasonality. We show seasonal variation in ASD births for the countries of Finland and Sweden. There was a modest increase in risk for children born in the fall and a modest decrease in risk for children born in the spring. Solar radiation levels around conception and the postnatal period were inversely correlated with seasonal trends in ASD risk. In the first multinational study of birth seasonality of ASD, there was evidence supporting the presence of seasonal trends in Finland and Sweden. The observations that risk was highest for fall births (i.e., conceived in the winter) and lowest for spring births (i.e., conceived in the summer), and sunlight levels during critical neurodevelopmental periods explained much of the seasonal trends, are consistent with the hypothesis that a seasonally fluctuating risk factor may influence risk of ASD.

Parental exposures to occupational asthmagens and risk of autism spectrum disorder in a Danish population-based case-control study.

BACKGROUND: Environmental exposures and immune conditions during pregnancy could influence development of autism spectrum disorder (ASD) in offspring. However, few studies have examined immune-triggering exposures in relation to ASD. We evaluated the association between parental workplace exposures to risk factors for asthma ("asthmagens") and ASD. METHODS: We conducted a population-based case-control study in the Danish population using register linkage. Our study population consisted of 11,869 ASD cases and 48,046 controls born from 1993 through 2007. Cases were identified by ICD-10 codes in the Danish Psychiatric Central Register. ASD cases and controls were linked to parental Danish International Standard Classification of Occupations (DISCO-88) job codes. Parental occupational asthmagen exposure was estimated by linking DISCO-88 codes to an asthma-specific job-exposure matrix. RESULTS: Our maternal analyses included 6706 case mothers and 29,359 control mothers employed during the pregnancy period. We found a weak inverse association between ASD and any maternal occupational asthmagen exposure, adjusting for sociodemographic covariates (adjusted OR: 0.92, 95% CI: 0.86-0.99). In adjusted analyses, including 7647 cases and 31,947 controls with employed fathers, paternal occupational asthmagen exposure was not associated with ASD (adjusted OR: 0.98, 95% CI: 0.92-1.05). CONCLUSIONS: We found a weak inverse association between maternal occupational asthmagen exposure and ASD, and a null association between paternal occupational exposure and ASD. We suggest that unmeasured confounding negatively biased the estimate, but that this unmeasured confounding is likely not strong enough to bring the effect above the null. Overall, our results were consistent with no positive association between parental asthmagen exposure and ASD in the children.

Early Elevation in Interleukin-6 is Associated with Reduced Growth in Extremely Low Birth Weight Infants.

Objective To determine whether reduced growth velocity (GV) in extremely low birth weight infants is preceded by elevated inflammatory cytokines. Study Design GV was determined at 36 weeks' postmenstrual age (PMA) in 768 infants 401 to 1,000 g birth weight (BW). Association between blood cytokines measured through day of life 21 and GV was explored using linear regression models that adjusted for late-onset sepsis (LOS), BW, small for gestational age (SGA), gender, race, energy intake, and center. Results Serum interleukin-6 (IL-6) was increased at days 14 and 21 in LOS infants. LOS was associated with reduced energy intake and GV for weight (weight-GV) at 36 weeks' PMA. Linear regression analysis controlling for LOS and energy intake showed significant relationships between increased IL-6 at days 14 and 21 with reduced weight-GV at 36 weeks' PMA (p < 0.0001). The relationship between day 21 IL-6 and weight-GV was not associated with LOS (p = 0.12) when controlling for BW and energy intake. Both BW (p = 0.02) and energy intake (p = 0.003) influenced the relationship between day 14 IL-6 and weight-GV. Conclusion IL-6 elevation during the first month of life is associated with lower weight-GV at 36 weeks' PMA and may have a direct effect upon energy balance and postnatal growth.

Presence of an epigenetic signature of prenatal cigarette smoke exposure in childhood.

Prenatal exposure to tobacco smoke has lifelong health consequences. Epigenetic signatures such as differences in DNA methylation (DNAm) may be a biomarker of exposure and, further, might have functional significance for how in utero tobacco exposure may influence disease risk. Differences in infant DNAm associated with maternal smoking during pregnancy have been identified. Here we assessed whether these infant DNAm patterns are detectible in early childhood, whether they are specific to smoking, and whether childhood DNAm can classify prenatal smoke exposure status. Using the Infinium 450K array, we measured methylation at 26 CpG loci that were previously associated with prenatal smoking in infant cord blood from 572 children, aged 3-5, with differing prenatal exposure to cigarette smoke in the Study to Explore Early Development (SEED). Striking concordance was found between the pattern of prenatal smoking associated DNAm among preschool aged children in SEED and those observed at birth in other studies. These DNAm changes appear to be tobacco-specific. Support vector machine classification models and 10-fold cross-validation were applied to show classification accuracy for childhood DNAm at these 26 sites as a biomarker of prenatal smoking exposure. Classification models showed prenatal exposure to smoking can be assigned with 81% accuracy using childhood DNAm patterns at these 26 loci. These findings support the potential for blood-derived DNAm measurements to serve as biomarkers for prenatal exposure.

The increasing prevalence of reported diagnoses of childhood psychiatric disorders: a descriptive multinational comparison.

The objective of this study is to compare the time trend of reported diagnoses of autism spectrum disorder (ASD), hyperkinetic disorder, Tourette's syndrome, and obsessive-compulsive disorder across four countries after standardizing the study period, diagnostic codes used to define the conditions and statistical analyses across countries. We use a population-based cohort, including all live-born children in Denmark, Finland, Sweden and Western Australia, from January 1, 1990, through December 31, 2007 and followed through December 31, 2011. The main outcome measure is age-specific prevalence of diagnoses reported to population-based registry systems in each country. We observe an increase in age-specific prevalence for reported diagnoses of all four disorders across birth-year cohorts in Denmark, Finland, Sweden, and (for ASD) Western Australia. Our results highlight the increase in the last 20 years in the number of children and families in contact with health care systems for diagnosis and services for an array of childhood neuropsychiatric disorders, a phenomenon not limited to ASD. Also, the age of diagnosis of the studied disorders was often much higher than what is known of the typical age of onset of symptoms, and we observe limited leveling off in the incidence rate with increasing age.

Congenital cerebral palsy and prenatal exposure to self-reported maternal infections, fever, or smoking.

OBJECTIVE: The objective of the study was to investigate the association between maternal self-reported infections, fever, and smoking in the prenatal period and the subsequent risk for congenital cerebral palsy (CP). STUDY DESIGN: We included the 81,066 mothers of singletons born between 1996 and 2003 who participated in the Danish National Birth Cohort. Children were followed up through December 2008. Information on maternal infections, fever, smoking, and other demographic and lifestyle factors during pregnancy were reported by mothers in computer-assisted telephone interviews in early and midgestation. We identified 139 CP cases including 121 cases of spastic CP (sCP) as confirmed by the Danish National Cerebral Palsy Register. Cox proportional hazards regression models were used to estimate adjusted hazard ratios (aHRs) and 95% confidence intervals (CIs). RESULTS: Self-reported vaginal infections were associated with an increased risk of CP and sCP (aHR, 1.52; 95% CI, 1.04-2.24; and aHR, 1.73; 95% CI, 1.16-2.60, respectively) and particularly untreated vaginal infections were associated with an increased risk of sCP (aHR, 1.95; 95% CI, 1.16-3.26). Fever was associated with the risk of CP (aHR, 1.53; 95% CI, 1.06-2.21). Smoking 10 or more cigarettes per day during pregnancy was also associated with sCP (aHR, 1.80; 95% CI, 1.10-2.94). There was a modest excess in risk for children exposed to both heavy smoking and vaginal infections. No other self-reported infections were significantly associated with CP. CONCLUSION: Self-reported vaginal infections, fever, and smoking 10 or more cigarettes per day during pregnancy were associated with a higher risk of overall CP and/or sCP.

Maternal infections during pregnancy and cerebral palsy: a population-based cohort study.

BACKGROUND: Cerebral palsy (CP) is a common motor disability in childhood. We examined the association between maternal infections during pregnancy and the risk of congenital CP in the child. METHODS: Liveborn singletons in Denmark between 1997 and 2003 were identified from the Danish National Birth Registry and followed from 1 year of life until 2008. Redemption of antibiotics from the National Register of Medicinal Product Statistics and maternal infections reported by the National Hospital Register were used as markers of maternal infection during pregnancy. CP diagnoses were obtained from the Danish Cerebral Palsy Registry. Adjusted hazard ratio (HR) and 95% confidence interval (CI) were estimated by Cox proportional hazard models. RESULTS: Of the 440 564 singletons with follow-up data, 840 were diagnosed with congenital CP. Maternal genito-urinary tract infections (HR 2.1, 95% CI 1.4, 3.2) were associated with CP in all births, in term births (HR 1.9, 95% CI 1.1, 3.2), in children with spastic CP (HR 2.1, 95% CI 1.4, 3.3), and among first-born children (HR 1.9, 95% CI 1.4, 3.3). Overall, we found associations between redeemed nitrofurantoin (HR 1.7, 95% CI 1.1, 2.8) and CP. Among trimester-specific exposures, CP risk was associated with prescriptions redeemed in the first trimester for any antibacterials, beta-lactam antibacterials, and nitrofurantoin, an antibiotic commonly used to treat lower urinary tract infection, and genito-urinary tract infections in the third trimester. CONCLUSION: Genito-urinary tract infections and antibiotic use during pregnancy were associated with increased risks of CP, indicating that some maternal infections or causes of maternal infections present in prenatal life may be part of a causal pathway leading to CP.

Big data in autism research: Methodological challenges and solutions.

While the concept of big data has emerged over the past decade as a hot topic in nearly all areas of scientific inquiry, it has rarely been discussed in the context of autism research. In this commentary we describe aspects of big data that are relevant to autism research and methodological issues such as confounding and data error that can hamper scientific investigation. Although big data studies can have transformative impact, bigger is not always better, and big data require the same methodological considerations and interdisciplinary collaboration as "small data" to extract useful scientific insight.

Using maternally reported data to investigate the association between early childhood infection and autism spectrum disorder: the importance of data source.

BACKGROUND: Childhood infections have been found to be associated with autism spectrum disorder (ASD) in previous studies using hospital data or medical records to identify infections. We aimed to replicate these findings using maternal reports of childhood infection. METHODS: We used the Danish National Birth Cohort consisting of 92 583 live singletons born from 1997 to 2003 in Denmark. ASD diagnoses were retrieved from the Danish Psychiatric Central Register, and a total of 945 children from the cohort were diagnosed with ASD. Data were analysed using Cox proportional hazards regression. We studied the association between ASD and maternal reports of infectious disease in the child from birth to 19 months. Furthermore, we performed secondary analyses using hospital registers to investigate the association between ASD and hospital contact in general as well as hospital contact for various infections. RESULTS: We did not find a general association between maternal reports of infectious illness and ASD. However, hospital contact for all causes was associated with an increased risk for an ASD diagnosis. Danish children with ASD do not appear to have a general pattern of illness from infection in early life, but do have more contact with medical specialists for infections and other indications compared with the general population. CONCLUSION: [corrected] Hospital data should be used cautiously when studying the co-morbidity of ASD; if the increased rate of hospital contact overall for children with ASD is not considered, then misleading interpretations might be made of observed associations between specific diseases and ASD.

Cytokines and posthemorrhagic ventricular dilation in premature infants.

OBJECTIVE: To determine in extremely low-birth-weight infants if elevated blood interferon-γ (IFN-γ), interleukin (IL)-1ß, IL-18, tumor necrosis factor-α (TNF-α), and transforming growth factor-ß are associated with need for shunt following severe intraventricular hemorrhage (IVH) or with ventricular dilation following milder grades/no IVH. STUDY DESIGN: Whole blood cytokines were measured on postnatal days 1, 3, 7, 14, and 21. Maximum IVH grade in the first 28 days, and shunt surgery or ventricular dilation on subsequent ultrasound (28 days' to 36 weeks' postmenstrual age) were determined. RESULTS: Of 902 infants in the National Institute of Child Health and Human Development Neonatal Research Network Cytokine study who survived to 36 weeks or discharge, 3.1% had shunts. Of the 12% of infants with severe (grade III to IV) IVH, 26% had a shunt associated with elevated TNF-α. None of the infants without IVH (69%) or with grade I (12%) or II (7%) IVH received shunts, but 8.4% developed ventricular dilation, associated with lower IFN-γ and higher IL-18. CONCLUSION: Statistically significant but clinically nondiscriminatory alterations in blood cytokines were noted in infants with severe IVH who received shunts and in those without severe IVH who developed ventricular dilation. Blood cytokines are likely associated with brain injury but may not be clinically useful as biomarkers for white matter damage.

T cell cytokines and the risk of blood stream infection in extremely low birth weight infants.

Cytokines mediate the host immune response to infectious micro-organisms. The objective of this study was to determine whether immune regulatory interleukins (IL-4, IL-5, IL-6, and IL-10) and inflammatory cytokines (Interferon-γ [INF-γ], tumor necrosis factor-ß [TNF-ß], IL-2, and IL-17) are associated with an increased risk of developing blood stream bacterial/fungal infection (BSI) in extremely low birth weight (ELBW) infants. ELBW infants from 17 NICHD Neonatal Research Network centers without early onset sepsis were studied. Cytokines were measured from blood on days 1, 3, 7, 14, and 21 after birth. 996 ELBW infants contributed a minimum of 4080 unique measurements for each cytokine during the five sampling periods. Infants with BSI had lower levels of the inflammatory cytokines IL-17 (p=0.01), and higher levels of the regulatory cytokines, IL-6 (p=0.01) and IL-10 (p<0.001). Higher levels of regulatory cytokines relative to pro-inflammatory cytokines were associated with increased risk of BSI even after adjusting for confounding variables. In ELBW infants, the ratio of immune regulatory cytokines to inflammatory cytokines was associated with development of BSI. Altered maturation of regulatory and inflammatory cytokines may increase the risk of serious infection in this population.

The co-occurrence of autism and birth defects: prevalence and risk in a population-based cohort.

AIM: To estimate the prevalence of major birth defects among children with autism, the prevalence of autism in children with birth defects, and the risk for autism associated with having birth defects. METHOD: Retrospective cohort including all children born in Atlanta, GA, USA, 1986 to 1993, who survived to age 3 years and were identified through Georgia vital records. Children with autism and other developmental disabilities residing in Atlanta at ages 3 to 10 years in 1996 were identified through the Metropolitan Atlanta Developmental Disabilities Surveillance Program. Children with major birth defects through age 6 years were identified by the Metropolitan Atlanta Congenital Defects Program. RESULTS: Birth defects were found among 6% of children with autism (total n=617; 488 males, 129 females) and was associated with a near twofold increased risk for autism overall. However, the risk magnitude and statistical significance varied by type of birth defect. With any type of birth defect, the risk for autism accompanied by intellectual disability or other developmental disabilities was typically higher than the risk for autism alone. A 6:1 to 8:1 male bias was observed among children with autism and a birth defect. INTERPRETATION: Investigation of the association between autism and birth defects is warranted, especially for the role of birth defects in autism among sex-specific or autism subgroups.

Family History of Mental and Neurological Disorders and Risk of Autism.

Importance: Familial aggregation of mental and neurological disorders is often observed in autism spectrum disorders (ASD), but reports have generally focused on single disorders and are limited to first-degree relatives. Objectives: To examine family history of mental and neurological disorders among first- to fourth-degree relatives and risk of ASD with and without intellectual disability (ID) in index persons. Design, Setting, and Participants: In this population-based cohort study, 567 436 index persons were identified from the Stockholm Youth Cohort, an ongoing longitudinal register-linkage cohort study of the total population aged 0 to 17 years residing in Stockholm County, Sweden. Index persons were nonadopted singleton births born between 1984 and 2009 who were at least 2 years of age at the end of follow-up on December 31, 2011, had resided in Stockholm County for at least 2 years since birth, and could be linked to both biological parents. Data analysis was conducted from May 2017 to December 2018. Exposure: Mental and neurological diagnoses of relatives of the index persons. Main Outcomes and Measures: Diagnosis of ASD, with or without co-occurring ID, in the index persons. Results: The cohort included 567 436 index persons (291 191 [51.3%] male; mean [SD] age at the end of follow-up, 14.3 [7.5] years). The prevalence of ASD with and without ID was 0.4% and 1.5%, respectively. Positive family history of mental and neurological disorders was associated with higher odds of ASD in index persons; 6895 (63.1%) of index persons with ASD had a parent with history of mental and/or neurological disorders, compared with 252 454 (45.4%) of index persons without ASD. Family history of multiple disorders was associated with higher odds of ASD in index persons, including history of ASD (odds ratio among first-degree relatives for ASD with and without ID: 14.2, 9.0), intellectual disability (7.6, 2.3), attention-deficit/hyperactivity disorder (3.3, 4.7), obsessive compulsive disorder (1.9, 2.1), schizophrenia and other nonaffective psychotic disorders (2.1, 1.8), depression (1.4, 2.0), bipolar disorder (1.4, 2.2), personality disorder (2.1, 2.6), cerebral palsy (2.2, 1.5), and epilepsy (2.0, 1.3). The more closely related the affected family member was, the higher the odds was of ASD for the index person. ASD without intellectual disability was associated with more disorders compared to ASD with intellectual disability. ASD with intellectual disability exhibited a weaker familial association with other mental disorder diagnoses but a stronger familial association with some neurological diagnoses as compared to ASD without intellectual disability. Conclusions and Relevance: This study suggests that family history of mental and neurological disorders is associated with increased risk of ASD. The familial component of ASD etiology may differ by presence or absence of co-occurring ID.

Parental Age and Differential Estimates of Risk for Neuropsychiatric Disorders: Findings From the Danish Birth Cohort.

OBJECTIVE: Parental age at birth has been shown to affect the rates of a range of neurodevelopmental disorders, but the understanding of the mechanisms through which it mediates different outcomes is still lacking. A population-based cohort was used to assess differential effects of parental age on estimates of risk across pediatric-onset neuropsychiatric disorders: autism spectrum disorder (ASD), attention-deficit/hyperactivity disorder (ADHD), obsessive-compulsive disorder (OCD), and Tourette's disorder/chronic tic disorder (TD/CT). METHOD: The study cohort included all singleton births in Denmark from 1980 through 2007 with full information on parental ages (N = 1,490,745) and was followed through December 31, 2013. Cases of ASD, ADHD, OCD, and TD/CT were identified in the Danish Psychiatric Central Register and the National Patient Register. Associations with parental age were modeled using a stratified Cox regression, allowing for changes in baseline diagnostic rates across time. RESULTS: Younger parental age was significantly associated with increased estimates of risk for ADHD and TD/CT, whereas older parental age was associated with ASD and OCD. Except for OCD, no evidence for differential effects of parental ages on male versus female offspring was observed. CONCLUSION: This study provides novel evidence for the association between age at parenthood and TD/CT and OCD and for the first time shows in a population-based sample that parental age confers differential risk rates for pediatric-onset psychiatric disorders. These results are consistent with a model of shared and unshared risk architecture for pediatric-onset neuropsychiatric conditions, highlighting unique contributions of maternal and paternal ages.

Recurrence Risk of Autism in Siblings and Cousins: A Multinational, Population-Based Study.

OBJECTIVE: Familial recurrence risk is an important population-level measure of the combined genetic and shared familial liability of autism spectrum disorder (ASD). Objectives were to estimate ASD recurrence risk among siblings and cousins by varying degree of relatedness and by sex. METHOD: This is a population-based cohort study of livebirths from 1998 to 2007 in California, Denmark, Finland, Israel, Sweden and Western Australia followed through 2011 to 2015. Subjects were monitored for an ASD diagnosis in their older siblings or cousins (exposure) and for their ASD diagnosis (outcome). The relative recurrence risk was estimated for different sibling and cousin pairs, for each site separately and combined, and by sex. RESULTS: During follow-up, 29,998 cases of ASD were observed among the 2,551,918 births used to estimate recurrence in ASD and 33,769 cases of childhood autism (CA) were observed among the 6,110,942 births used to estimate CA recurrence. Compared with the risk in unaffected families, there was an 8.4-fold increase in the risk of ASD following an older sibling with ASD and a 17.4-fold increase in the risk of CA following an older sibling with CA. A 2-fold increase in the risk for cousin recurrence was observed for the 2 disorders. There also was a significant difference in sibling ASD recurrence risk by sex. CONCLUSION: The present estimates of relative recurrence risks for ASD and CA will assist clinicians and families in understanding autism risk in the context of other families in their population. The observed variation by sex underlines the need to deepen the understanding of factors influencing ASD familial risk.

Association of preterm birth with sustained postnatal inflammatory response.

OBJECTIVE: To investigate fetal or neonatal inflammatory patterns based on 25 inflammatory markers in neonatal dried blood spots samples from infants born preterm and term, collected several days after birth. METHODS: Dried blood spots samples from 160 neonates were analyzed for 25 inflammatory markers using multiplex technology: 26 neonates born very preterm (before 32 weeks of gestation), drawn at a mean 6 days (95% confidence interval [CI], 5-7 days) after birth; 52 born preterm (32-36 weeks of gestation), drawn at mean 5 days (95% CI, 5-6 days) after birth; and 82 born at term (at or after 37 weeks of gestation), drawn at mean 5 days (95% CI, 5-5 days) after birth. Markers statistically significantly associated with preterm birth were analyzed in a multivariable model together with maternal and neonatal risk factors for preterm birth. RESULTS: Elevated levels of interleukin (IL)-1beta, IL-6, soluble IL-6ralpha, IL-8, matrix metalloproteinase-9, and transforming growth factor-beta1 and decreased levels of IL-18, brain-derived neurotrophic factor, and C-reactive protein were associated with preterm birth. Maternal risk factors could explain only an increase of IL-1beta, whereas neonatal factors could explain several of the elevated and decreased inflammatory markers in the dried blood spots samples from the infants born preterm compared with the infants born at term. CONCLUSION: The differences in levels of inflammatory markers in dried blood spots samples from infants born preterm compared with infants born at term supports the hypothesis that inflammation of fetal origin might be a cause of preterm birth. LEVEL OF EVIDENCE: II.

Serum macrophage migration inhibitory factor in the prediction of preterm delivery.

OBJECTIVE: Macrophage migration inhibitory factor is a soluble mediator that helps govern the interaction between cytokines and stress hormones (eg, cortisol). We determined whether maternal macrophage migration inhibitory factor levels predicted subsequent preterm delivery. STUDY DESIGN: A nested case-control study measuring serum macrophage migration inhibitory factor concentration at 9-23 weeks' gestation in women who ultimately delivered preterm (n = 60) compared with control women who delivered at term (n = 122). We also examined the connection of macrophage migration inhibitory factor with self-reported psychosocial variables. RESULTS: Macrophage migration inhibitory factor was elevated in the preterm delivery cases (P = .0004), and log macrophage migration inhibitory factor concentration showed a graded response relationship with likelihood of preterm delivery. High-macrophage migration inhibitory factor was also associated with maternal risk-taking behavior, which itself was a risk factor for preterm delivery. Macrophage migration inhibitory factor remained associated independently with preterm delivery after adjusting regression models for several other preterm delivery risk factors (odds ratio, 3.11, 95% confidence interval, 1.54-6.30). CONCLUSION: High-serum macrophage migration inhibitory concentration in early to midpregnancy is linked with subsequent preterm delivery.

Case-control meta-analysis of blood DNA methylation and autism spectrum disorder.

Background: Several reports have suggested a role for epigenetic mechanisms in ASD etiology. Epigenome-wide association studies (EWAS) in autism spectrum disorder (ASD) may shed light on particular biological mechanisms. However, studies of ASD cases versus controls have been limited by post-mortem timing and severely small sample sizes. Reports from in-life sampling of blood or saliva have also been very limited in sample size and/or genomic coverage. We present the largest case-control EWAS for ASD to date, combining data from population-based case-control and case-sibling pair studies. Methods: DNA from 968 blood samples from children in the Study to Explore Early Development (SEED 1) was used to generate epigenome-wide array DNA methylation (DNAm) data at 485,512 CpG sites for 453 cases and 515 controls, using the Illumina 450K Beadchip. The Simons Simplex Collection (SSC) provided 450K array DNAm data on an additional 343 cases and their unaffected siblings. We performed EWAS meta-analysis across results from the two data sets, with adjustment for sex and surrogate variables that reflect major sources of biological variation and technical confounding such as cell type, batch, and ancestry. We compared top EWAS results to those from a previous brain-based analysis. We also tested for enrichment of ASD EWAS CpGs for being targets of meQTL associations using available SNP genotype data in the SEED sample. Findings: In this meta-analysis of blood-based DNA from 796 cases and 858 controls, no single CpG met a Bonferroni discovery threshold of p < 1.12 × 10- 7. Seven CpGs showed differences at p < 1 × 10- 5 and 48 at 1 × 10- 4. Of the top 7, 5 showed brain-based ASD associations as well, often with larger effect sizes, and the top 48 overall showed modest concordance (r = 0.31) in direction of effect with cerebellum samples. Finally, we observed suggestive evidence for enrichment of CpG sites controlled by SNPs (meQTL targets) among the EWAS CpG hits, which was consistent across EWAS and meQTL discovery p value thresholds. Conclusions: No single CpG site showed a large enough DNAm difference between cases and controls to achieve epigenome-wide significance in this sample size. However, our results suggest the potential to observe disease associations from blood-based samples. Among the seven sites achieving suggestive statistical significance, we observed consistent, and stronger, effects at the same sites among brain samples. Discovery-oriented EWAS for ASD using blood samples will likely need even larger samples and unified genetic data to further understand DNAm differences in ASD.