Attainment and loss of early social-communication skills across neurodevelopmental conditions in the Norwegian Mother, Father and Child Cohort Study.

BACKGROUND: Delays and loss of early-emerging social-communication skills are often discussed as unique to autism. However, most studies of regression have relied on retrospective recall and clinical samples. Here, we examine attainment and loss of social-communication skills in the population-based Norwegian Mother, Father and Child Cohort Study (MoBa). METHODS: Mothers rated their child's attainment of 10 early-emerging social-communication skills at ages 18 and 36 months (N = 40,613, 50.9% male). Prospectively reported loss was defined as skill presence at 18 months but absence at 36 months. At 36 months, mothers also recalled whether the child had lost social-communication skills. The Norwegian Patient Registry was used to capture diagnoses of Autism Spectrum Disorder (autism) and other neurodevelopmental disabilities (NDDs). RESULTS: Delay in at least one skill was observed in 14% of the sample and loss in 5.4%. Recalled loss of social-communication skills was rare (0.86%) and showed low convergence with prospectively reported loss. Delay and especially loss were associated with elevated odds of an autism diagnosis (n = 383) versus no autism diagnosis (n = 40,230; ≥3 skills delayed: OR = 7.09[4.15,12.11]; ≥3 skills lost: OR = 30.66[17.30,54.33]). They were also associated with an increased likelihood of autism compared to some other NDDs. Delay (relative risk [RR] = 4.16[2.08, 8.33]) and loss (RR = 10.00[3.70, 25.00]) associated with increased likelihood of autism versus ADHD, and loss (RR = 4.35[1.28,14.29]), but not delay (RR = 2.00[0.78,5.26]), associated with increased likelihood of autism compared to language disability. Conversely, delay conferred decreased likelihood of autism versus intellectual disability (RR = 0.11[0.06,0.21]), and loss was not reliably associated with likelihood of autism versus intellectual disability (RR = 1.89[0.44,8.33]). CONCLUSIONS: This population-based study suggests that loss of early social communication skills is more common than studies using retrospective reports have indicated and is observed across several NDD diagnoses (not just autism). Nevertheless, most children with NDD diagnoses showed no reported delay or loss in these prospectively measured skills.

Disruptive Mood Dysregulation Disorder in a Norwegian Clinical Child Population.

BACKGROUND: Disruptive Mood Dysregulation Disorder was included in DSM-5 to accommodate new research addressing aspects of emotional dysregulation in children suffering from disruptive behavior problems. Despite growing interest in Disruptive Mood Dysregulation Disorder, few studies have looked at prevalence rates in European clinical populations. The primary objective of this study was to examine the prevalence and characteristics associated with Disruptive Mood Dysregulation Disorder in a Norwegian clinical sample. METHODS: The present study assessed children 6-12 years of age referred to a mental health clinic for evaluation and treatment (N = 218, Mage = 9.6, 60.4% boys) and compared those who did and did not meet Disruptive Mood Dysregulation Disorder diagnostic criteria. Diagnoses were determined using K-SADS-PL 2013. Associated difficulties at home and in school were measured by Achenbach Systems of Empirically Based Assessment battery. RESULTS: In this clinical sample, 24% met the diagnostic criteria for Disruptive Mood Dysregulation Disorder. Children with Disruptive Mood Dysregulation Disorder were more likely than those without Disruptive Mood Dysregulation Disorder to be male (77% vs. 55%, p = .008), be living in poverty, have multiple mental health diagnoses (79% vs. 53%, p = .001), and have lower global functioning levels as measured by Children's Global Assessment Scale (range 0-100, M = 47, SD = 8.5 vs. M = 57, SD = 11.4, p=<.001). Finally, parents and teachers of children with Disruptive Mood Dysregulation Disorder reported lower overall competence and adaptive functioning, and higher total symptom load than children with other diagnoses. CONCLUSION: Disruptive Mood Dysregulation Disorder is highly prevalent in a Norwegian clinical sample and displays a high symptom load. Our results are in accordance with similar studies. Consistent findings across the world may support Disruptive Mood Dysregulation Disorder as a valid diagnostic category.

Measuring autism-associated traits in the general population: Factor structure and measurement invariance across sex and diagnosis status of the Social Communication Questionnaire.

LAY ABSTRACT: Using questionnaires in research relies on the expectation that they measure the same things across different groups of individuals. If this is not true, then interpretations of results can be misleading when researchers compare responses across different groups of individuals or use in it a group that differs from that in which the questionnaire was developed. For the questionnaire we investigated, the Social Communication Questionnaire (SCQ), we found that parents of boys and girls responded to questionnaire items in largely the same way but that the SCQ measured traits and behaviors slightly differently depending on whether the children had autism. Based on these results, we concluded that researchers using this questionnaire should carefully consider these differences when deciding how to interpret findings. SCQ scores as a reflection of "autism-associated traits" in samples that are mostly or entirely made up of individuals without an autism diagnosis may be misleading and we encourage a more precise interpretation of scores as a broader indication of social-communicative and behavioral traits.

Developmental milestones in early childhood and genetic liability to neurodevelopmental disorders.

BACKGROUND: Timing of developmental milestones, such as age at first walking, is associated with later diagnoses of neurodevelopmental disorders. However, its relationship to genetic risk for neurodevelopmental disorders in the general population is unknown. Here, we investigate associations between attainment of early-life language and motor development milestones and genetic liability to autism, attention deficit hyperactivity disorder (ADHD), and schizophrenia. METHODS: We use data from a genotyped sub-set (N = 25699) of children in the Norwegian Mother, Father and Child Cohort Study (MoBa). We calculate polygenic scores (PGS) for autism, ADHD, and schizophrenia and predict maternal reports of children's age at first walking, first words, and first sentences, motor delays (18 months), and language delays and a generalised measure of concerns about development (3 years). We use linear and probit regression models in a multi-group framework to test for sex differences. RESULTS: We found that ADHD PGS were associated with earlier walking age (ß = -0.033, padj < 0.001) in both males and females. Additionally, autism PGS were associated with later walking (ß = 0.039, padj = 0.006) in females only. No robust associations were observed for schizophrenia PGS or between any neurodevelopmental PGS and measures of language developmental milestone attainment. CONCLUSIONS: Genetic liabilities for neurodevelopmental disorders show some specific associations with the age at which children first walk unsupported. Associations are small but robust and, in the case of autism PGS, differentiated by sex. These findings suggest that early-life motor developmental milestone attainment is associated with genetic liability to ADHD and autism in the general population.

Associations Between Pregnancy-Related Predisposing Factors for Offspring Neurodevelopmental Conditions and Parental Genetic Liability to Attention-Deficit/Hyperactivity Disorder, Autism, and Schizophrenia: The Norwegian Mother, Father and Child Cohort Study (MoBa).

Importance: Several maternal exposures during pregnancy are considered predisposing factors for offspring neurodevelopmental conditions. However, many of these exposures may be noncausal and biased by maternal genetic liability. Objective: To assess whether pregnancy-related predisposing factors for offspring neurodevelopmental conditions are associated with maternal genetic liability for attention-deficit/hyperactivity disorder (ADHD), autism, and schizophrenia and to compare associations for maternal genetic liability with those for paternal genetic liability, which could indicate that paternal exposures are not suitable negative controls for maternal exposures. Design, Setting, and Participants: The Norwegian Mother, Father and Child Cohort Study (MoBa) is a population-based pregnancy cohort that recruited parents from June 1999 to December 2008. Polygenic scores (PGS) for ADHD, autism, and schizophrenia were derived in mothers and fathers. The associations between maternal PGS and 37 pregnancy-related measures were estimated, and these results were compared with those from paternal PGS predicting paternal measures during the mother's pregnancy. Analysis took place between March 2021 and March 2022. Exposures: PGS for ADHD, autism, and schizophrenia, calculated (using discovery effect size estimates and threshold of P < .05) from the largest available genome-wide association studies. Main Outcomes and Measures: Self-reported pregnancy-related measures capturing lifestyle behaviors, metabolism, infectious and autoimmune diseases, other physical health conditions, and medication use. Results: Data were available for up to 14 539 mothers (mean [SD] age, 30.00 [4.45] years) and 14 897 fathers (mean [SD] age, 32.46 [5.13] years) of European ancestry. Modest but robust associations were observed between specific pregnancy-related measures and maternal PGS, including ADHD PGS with asthma (odds ratio [OR], 1.15 [95% CI, 1.06-1.25]), smoking (OR, 1.26 [95% CI, 1.19-1.33]), prepregnancy body mass index (ß, 0.25 [95% CI, 0.18-0.31]), pregnancy weight gain (ß, 0.20 [95% CI, 0.10-0.30]), taking folate (OR, 0.92 [95% CI, 0.88-0.96]), and not taking supplements (OR, 1.09 [95% CI, 1.04-1.14]). Schizophrenia PGS was associated with coffee consumption (OR, 1.09 [95% CI, 1.05-1.12]), smoking (OR, 1.12 [95% CI, 1.06-1.19]), prepregnancy body mass index (ß, -0.18 [95% CI, -0.25 to -0.11]), and pregnancy weight gain (ß, 0.17 [95% CI, 0.07-0.27]). All 3 PGSs associated with symptoms of depression/anxiety (ADHD: OR, 1.15 [95% CI, 1.09-1.22]; autism: OR, 1.13 [95% CI, 1.06-1.19]; schizophrenia: OR, 1.13 [95% CI, 1.07-1.20]). Associations were largely consistent for maternal and paternal PGS, except ADHD PGS and smoking (fathers: OR, 1.13 [95% CI, 1.09-1.17]). Conclusions and Relevance: In this study, genetic liability to neurodevelopmental conditions that is passed from mothers to children was associated with several pregnancy-related factors and may therefore confound associations between these pregnancy-related factors and offspring neurodevelopment that have previously been thought to be causal. It is crucial that future study designs account for genetic confounding to obtain valid causal inferences so that accurate advice can be given to pregnant individuals.

Genetic Liability for Schizophrenia and Childhood Psychopathology in the General Population.

Genetic liability for schizophrenia is associated with psychopathology in early life. It is not clear if these associations are time dependent during childhood, nor if they are specific across different forms of psychopathology. Using genotype and questionnaire data on children (N = 15 105) from the Norwegian Mother, Father and Child Cohort Study, we used schizophrenia polygenic risk scores to test developmental stability in associations with measures of emotional and behavioral problems between 18 months and 5 years, and domain specificity in associations with symptoms of depression, anxiety, conduct problems, oppositionality, inattention, and hyperactivity at 8 years. We then sought to identify symptom profiles-across development and domains-associated with schizophrenia polygenic liability. We found evidence for developmental stability in associations between schizophrenia polygenic risk scores and emotional and behavioral problems, with the latter being mediated specifically via the rate of change in symptoms (ß slope = 0.032; 95% CI: 0.007-0.057). At age 8, associations were better explained by a model of symptom-specific polygenic effects rather than effects mediated via a general psychopathology factor or by domain-specific factors. Overall, individuals with higher schizophrenia polygenic risk scores were more likely (OR = 1.310 [95% CIs: 1.122-1.528]) to have a profile of increasing behavioral and emotional symptoms in early childhood, followed by elevated symptoms of conduct disorder, oppositionality, hyperactivity, and inattention by age 8. Schizophrenia-associated alleles are linked to specific patterns of early-life psychopathology. The associations are small, but findings of this nature can help us better understand the developmental emergence of schizophrenia.

Functional Outcomes of Children Identified Early in the Developmental Period as at Risk for ASD Utilizing the The Norwegian Mother, Father and Child Cohort Study (MoBa).

Early identification of autism spectrum disorder (ASD) is regarded as crucial for swift access to early intervention and, subsequently, better outcomes later in life. However, current instruments miss large proportions of children who later go on to be diagnosed with ASD, raising a question of what these instruments measure. The present study utilized data from the Norwegian Mother, Father, and Child Cohort Study and the Autism Birth Cohort study to explore the subsequent developmental and diagnostic characteristics of children raising developmental concern on the six-critical discriminative item criterion of the M-CHAT (DFA6) at 18 months of age (N = 834). The DFA6 identified 28.8% of children diagnosed with ASD (N = 163), but 4.4% with language disorder (N = 188) and 81.3% with intellectual disability (N = 32) without ASD. Scoring in the «at-risk¼ range was associated with lower IQ, impaired functional language, and greater severity of autism symptoms whether children had ASD or not.

Age of walking and intellectual ability in autism spectrum disorder and other neurodevelopmental disorders: a population-based study.

BACKGROUND: Delayed walking is common in intellectual disability (ID) but may be less common when ID occurs with autism spectrum disorder (ASD). Previous studies examining this were limited by reliance on clinical samples and exclusion of children with severe motor deficits. OBJECTIVE: To examine in a population-based sample if age of walking is differentially related to intellectual ability in children with ASD versus other neurodevelopmental disorders (NDD). METHODS: Participants were from the nested Autism Birth Cohort Study of the Norwegian Mother, Father and Child Cohort Study (MoBa). Cox proportional hazards regression assessed if diagnosis (ASD n = 212 vs. NDD n = 354), continuous nonverbal IQ, and their interaction, were associated with continuous age of walking. RESULTS: The relationship between nonverbal IQ and age of walking was stronger for NDD than for ASD (Group × nonverbal IQ interaction, χ2  = 13.93, p = .0002). This interaction was characterized by a 21% decrease in the likelihood of walking onset at any given time during the observation period per 10-point decrease in nonverbal IQ (hazard ratio = 0.79, 95% CI: 0.78-0.85) in the NDD group compared to 8% (hazard ratio = 0.92, 95% CI: 0.86-0.98) in the ASD group. CONCLUSIONS: The finding that age of walking is less strongly related to low intellectual ability in children with ASD than in children without other NDDs supports the hypothesis that ID in ASD may result from heterogeneous developmental pathways. Late walking may be a useful stratification variable in etiological research focused on ASD and other NDDs.

Diagnosing autism spectrum disorder among children in Norway. / Diagnostisering av autismespekterforstyrrelser hos barn i Norge.

BACKGROUND: The percentage share of children who are diagnosed with autism spectrum disorder has increased considerably since the 1990s in Norway as well as in other countries. It has previously been demonstrated that there is considerable variation between counties with respect to diagnostic practice. MATERIAL AND METHOD: We calculated the percentage of children with autism spectrum disorder by using patient data obtained from the Norwegian Patient Registry and population data obtained from the National Registry. The calculations were made for the country as a whole as well as by county. The diagnostic assessments and documentation were mapped by linking the Norwegian Patient Registry with the Norwegian Mother, Father and Child Cohort study. We also reviewed patient records obtained from the specialist health service and considered whether diagnostic practice satisfied the research criteria for autism spectrum disorder. RESULTS: By the age of eight, 1.1 % of boys and 0.3 % of girls had been diagnosed with autism spectrum disorder. The overall percentages varied from 0.3 to 1.0 between counties. From 2008 to 2016, these percentages increased in all age groups. Our review of patient records included 503 children. In 95 % of cases the patient records provided a high standard of documentation that the diagnostic research criteria had been satisfied. The assessments were largely conducted in accordance with the guidelines drawn up by the various health trusts. INTERPRETATION: Autism diagnoses are generally well documented within the Norwegian specialist health service and meet the diagnostic criteria. In the counties that demonstrate a low prevalence of autism, it appears the health service fails to recognise autism in many children, particularly girls, or the diagnosis is determined late.

Sensitivity and specificity of early screening for autism.

BACKGROUND: Early identification and diagnosis is beneficial for children with autism spectrum disorder (ASD). Universal early screening is recommended by many experts, but disputed because evidence is limited, and sensitivity and specificity in general populations are largely unknown. AIMS: To estimate the sensitivity and specificity of early population-based screening for ASDs. METHOD: The study was based on the Norwegian Mother and Child Cohort Study. The 36-month cohort questionnaire included the Social Communication Questionnaire (SCQ), a 40-item screening instrument for ASD. RESULTS: A total of 58 520 mothers (58%) responded to the questionnaire. By the end of follow-up on 31 December 2015, 385 (0.7%) individuals with ASD had been identified among the responders' children. The distributions of SCQ scores in those with ASD and other children had large degrees of overlap. With the cut-off of 15 recommended in the SCQ manual, screening sensitivity was 20% (95% CI 16-24) for ASD overall. For children with ASD who had not developed phrase speech at 36 months, sensitivity was 46% (95% CI 35-57%), whereas it was 13% (95% CI 9-17) for children with ASD with phrase speech. Screening specificity was 99% (95% CI 99-99). With the currently recommended cut-off of 11, sensitivity increased to 42% for ASD overall (95% CI 37-47), 69% (95% CI 58-79) for ASD without phrase speech and 34% (95% CI 29-40) for ASD with phrase speech. Specificity was then reduced to 89% (95% CI 89-90). CONCLUSIONS: Early ASD screening with a parent checklist had low sensitivity. It identified mainly individuals with ASD with significant developmental delay and captured very few children with ASD with cognitive skills in the normal range. Increasing sensitivity was not possible without severely compromising specificity. DECLARATION OF INTEREST: C.L. receives royalty for the Social Communication Questionnaire, which she has co-authored.

Clinical Features of Children With Autism Who Passed 18-Month Screening.

OBJECTIVES: We compared sex-stratified developmental and temperamental profiles at 18 months in children screening negative for autism spectrum disorder (ASD) on the Modified Checklist for Autism in Toddlers (M-CHAT) but later receiving diagnoses of ASD (false-negative group) versus those without later ASD diagnoses (true-negative group). METHODS: We included 68 197 screen-negative cases from the Norwegian Mother and Child Cohort Study (49.1% girls). Children were screened by using the 6 critical items of the M-CHAT at 18 months. Groups were compared on domains of the Ages and Stages Questionnaire and the Emotionality Activity Sociability Temperament Survey. RESULTS: Despite passing M-CHAT screening at 18 months, children in the false-negative group exhibited delays in social, communication, and motor skills compared with the true-negative group. Differences were more pronounced in girls. However, with regard to shyness, boys in the false-negative group were rated as more shy than their true-negative counterparts, but girls in the false-negative group were rated as less shy than their counterparts in the true-negative group. CONCLUSIONS: This is the first study to reveal that children who pass M-CHAT screening at 18 months and are later diagnosed with ASD exhibit delays in core social and communication areas as well as fine motor skills at 18 months. Differences appeared to be more pronounced in girls. With these findings, we underscore the need to enhance the understanding of early markers of ASD in boys and girls, as well as factors affecting parental report on early delays and abnormalities, to improve the sensitivity of screening instruments.

The influence of parental concern on the utility of autism diagnostic instruments.

The parental report-based Autism Diagnostic Interview-Revised (ADI-R) and the clinician observation-based Autism Diagnostic Observation Schedule (ADOS) have been validated primarily in U.S. clinics specialized in autism spectrum disorder (ASD), in which most children are referred by their parents because of ASD concern. This study assessed diagnostic agreement of the ADOS-2 and ADI-R toddler algorithms in a more broadly based sample of 679 toddlers (age 35-47 months) from the Norwegian Mother and Child Cohort. We also examined whether parental concern about ASD influenced instrument performance, comparing toddlers identified based on parental ASD concern (n = 48) and parent-reported signs of developmental problems (screening) without a specific concern about ASD (n = 400). The ADOS cutoffs showed consistently well-balanced sensitivity and specificity. The ADI-R cutoffs demonstrated good specificity, but reduced sensitivity, missing 43% of toddlers whose parents were not specifically concerned about ASD. The ADI-R and ADOS dimensional scores agreed well with clinical diagnoses (area under the curve ≥ 0.85), contributing additively to their prediction. On the ADI-R, different cutoffs were needed according to presence or absence of parental ASD concern, in order to achieve comparable balance of sensitivity and specificity. These results highlight the importance of taking parental concern about ASD into account when interpreting scores from parental report-based instruments such as the ADI-R. While the ADOS cutoffs performed consistently well, the additive contributions of ADI-R and ADOS scores to the prediction of ASD diagnosis underscore the value of combining instruments based on parent accounts and clinician observation in evaluation of ASD. Autism Res 2017, 10: 1672-1686. © 2017 International Society for Autism Research, Wiley Periodicals, Inc.

Correction for Mahic et al., "Maternal Immunoreactivity to Herpes Simplex Virus 2 and Risk of Autism Spectrum Disorder in Male Offspring".

[This corrects the article DOI: 10.1128/mSphere.00016-17.].

Maternal Immunoreactivity to Herpes Simplex Virus 2 and Risk of Autism Spectrum Disorder in Male Offspring.

Maternal infections during pregnancy are associated with risk of neurodevelopmental disorders, including autism spectrum disorders (ASDs). Proposed pathogenetic mechanisms include fetal infection, placental inflammation, and maternal cytokines or antibodies that cross the placenta. The Autism Birth Cohort comprises mothers, fathers, and offspring recruited in Norway in 1999 to 2008. Through questionnaire screening, referrals, and linkages to a national patient registry, 442 mothers of children with ASD were identified, and 464 frequency-matched controls were selected. Immunoglobulin G (IgG) antibodies to Toxoplasma gondii, rubella virus, cytomegalovirus (CMV), herpes simplex virus 1 (HSV-1), and HSV-2 in plasma collected at midpregnancy and after delivery were measured by multiplexed immunoassays. High levels of HSV-2 IgG antibodies in maternal midpregnancy plasma were associated with increased risk of ASD in male offspring (an increase in HSV-2 IgG levels from 240 to 640 arbitrary units/ml was associated with an odds ratio of 2.07; 95% confidence interval, 1.06 to 4.06; P = 0.03) when adjusted for parity and child's birth year. No association was found between ASD and the presence of IgG antibodies to Toxoplasma gondii, rubella virus, CMV, or HSV-1. Additional studies are needed to test for replicability of risk and specificity of the sex effect and to examine risk associated with other infections. IMPORTANCE The cause (or causes) of most cases of autism spectrum disorder is unknown. Evidence from epidemiological studies and work in animal models of neurodevelopmental disorders suggest that both genetic and environmental factors may be implicated. The latter include gestational infection and immune activation. In our cohort, high levels of antibodies to herpes simplex virus 2 at midpregnancy were associated with an elevated risk of autism spectrum disorder in male offspring. These findings provide support for the hypothesis that gestational infection may contribute to the pathogenesis of autism spectrum disorder and have the potential to drive new efforts to monitor women more closely for cryptic gestational infection and to implement suppressive therapy during pregnancy.

Multidimensional Influences on Autism Symptom Measures: Implications for Use in Etiological Research.

OBJECTIVE: Growing awareness that symptoms of autism spectrum disorder (ASD) transcend multiple diagnostic categories, and major advances in the identification of genetic syndromes associated with ASD, have led to widespread use of ASD symptom measures in etiologic studies of neurodevelopmental disorders. Insufficient consideration of potentially confounding factors such as cognitive ability or behavior problems can have important negative consequences in interpretation of findings, including erroneous estimation of associations between ASD and etiologic factors. METHOD: Participants were 388 children 2 to 13 years old with diagnoses of ASD or another neurodevelopmental disorder without ASD. Receiver operating characteristics methods were used to assess the influence of IQ and emotional and behavioral problems on the discriminative ability of 3 widely used ASD symptom measures: the Social Responsiveness Scale (SRS), the Autism Diagnostic Interview-Revised (ADI-R), and the Autism Diagnostic Observation Schedule (ADOS). RESULTS: IQ influenced the discriminative thresholds of the SRS and ADI-R, and emotional and behavioral problems affected the discriminative thresholds of the SRS, ADI-R, and ADOS. This resulted in low specificity of ASD cutoffs on the SRS and ADI-R for children with intellectual disability without ASD (27-42%) and low specificity across all 3 instruments for children without ASD with increased emotional and behavioral problems (36-59%). Adjustment for these characteristics resulted in improved discriminative ability for all of the ASD measures. CONCLUSION: The findings indicate that scores on ASD symptom measures reflect far more than ASD symptoms. Valid interpretation of scores on these measures requires steps to account for the influences of IQ and emotional and behavioral problems.

Parental obesity and risk of autism spectrum disorder.

OBJECTIVES: The objective of the study was to investigate the associations among maternal prepregnancy BMI, paternal BMI, and the risk of autism spectrum disorders (ASDs) in children. METHODS: The study sample of 92 909 children was derived from the population-based, prospective Norwegian Mother and Child Cohort Study. The age range was 4.0 through 13.1 (mean 7.4) years. Relative risks of ASDs were estimated by odds ratios (ORs) and 95% confidence intervals (CIs) from logistic regression models. RESULTS: At the end of follow-up on December 31, 2012, 419 children in the study sample had been diagnosed with ASDs: 162 with autistic disorder, 103 with Asperger disorder, and 154 with pervasive developmental disorder not otherwise specified. Maternal obesity (BMI ≥30) was only weakly associated with ASD risk, whereas paternal obesity was associated with an increased risk of autistic disorder and Asperger disorder. The risk of autistic disorder was 0.27% (25 of 9267) in children of obese fathers and 0.14% (59 of 41 603) in children of fathers with normal weight (BMI <25), generating an adjusted OR of 1.73 (95% CI: 1.07-2.82). For Asperger disorder, analyses were limited to children aged ≥7 years (n = 50 116). The risk was 0.38% (18 of 4761) in children of obese fathers and 0.18% (42 of 22 736) in children of normal-weight fathers, and the adjusted OR was 2.01 (95% CI: 1.13-3.57). No associations were found for pervasive developmental disorder not otherwise specified. CONCLUSIONS: Paternal obesity is an independent risk factor for ASDs in children. The associations should be investigated further in genetic and epigenetic studies.

Identifying children with autism spectrum disorder at 18 months in a general population sample.

BACKGROUND: Previous research on clinical and high-risk samples suggests that signs of autism spectrum disorder (ASD) can be detected between 1 and 2 years of age. We investigated signs of ASD at 18 months in a population-based sample and the association with later ASD diagnosis. METHODS: The study sample includes 52,026 children born 2003 through 2008 and is a subset of children that participated in the Norwegian Mother and Child Cohort (MoBa), a population-based longitudinal study, and the Autism Birth Cohort (ABC), a sub-study on ASD. Parents completed all 23 items from the Modified Checklist for Autism in Toddlers (M-CHAT) at 18 months. RESULTS: The M-CHAT 6-critical-item criterion and the 23-item criterion had a specificity of 97.9% and 92.7% and a sensitivity of 20.8% and 34.1%, respectively. In the 173 children diagnosed with ASD to date, 60 children (34.7%) scored above the cut-off on either of the screening criteria. The items with the highest likelihood ratios were 'interest in other children', 'show objects to others' and 'response to name'. CONCLUSION: Even though one-third of the children who later received an ASD diagnosis were identified through M-CHAT items, the majority scored below cut-off on the screening criteria at 18 months. The results imply that it might not be possible to detect all children with ASD at this age.