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In recent years, the United States has been experiencing historically high suicide rates. In the face of mental health care provider shortages that leave millions needing to travel longer to find providers with schedule openings, if any are available at all, the inaccessibility of mental health care has become increasingly central in explaining suicidality. To examine the relationship between access to care and suicide, we leverage a dataset mapping all licensed US psychiatrists and psychotherapists (N= 711,214), as of early 2020, and employ real-world transportation data to model patients' mobility barriers. We find a strong association between reduced mental health care provider spatial-social accessibility and heightened suicide risk. Using a machine learning approach to condition on a host of 22 contextual factors known to be implicated in suicide (e.g., race, education, divorce, gun shop prevalence), we find that in locales where individuals seeking care can access fewer mental health care providers, already more likely to be saturated by demand, suicide risk is increased (3.2% for each reduced SD of psychiatrist accessibility; 2.3% for psychotherapists). Additionally, we observe that local spatial-social accessibility inequalities are associated with further heightened risk of suicide, underscoring the need for research to account for the highly localized barriers preventing many Americans from accessing needed mental health services.
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Serviços de Saúde Mental , Suicídio , Humanos , Estados Unidos , Acessibilidade aos Serviços de Saúde , Saúde Mental , Ideação SuicidaRESUMO
This article sheds light on how to capture knowledge integration dynamics in college course content, improves and enriches the definition and measurement of interdisciplinarity, and expands the scope of research on the benefits of interdisciplinarity to postcollege outcomes. We distinguish between what higher education institutions claim regarding interdisciplinarity and what they appear to actually do. We focus on the core academic element of student experience-the courses they take, develop a text-based semantic measure of interdisciplinarity in college curriculum, and test its relationship to average earnings of graduates from different types of schools of higher education. We observe that greater exposure to interdisciplinarity-especially for science majors-is associated with increased earnings after college graduation.
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Currículo , Estudos Interdisciplinares , Humanos , Universidades , Estudantes , Instituições AcadêmicasRESUMO
As rates of autism diagnosis increased dramatically over the past number of decades, prevalence rates were generally highest among Whites and among those of higher socioeconomic status (SES). Using a unique, population-level dataset, we find that rates of autism diagnosis continued to be on the rise in recent years, but who is diagnosed changed during the study period. Our data consist of birth records of all 13,272,573 children born in the state of California in 1992 through 2016 linked to autism caseload records for January 1992 through November 2019 from California's Department of Developmental Services. California's diagnosed autism incidence rate rose from 0.49 per 1,000 3-6 y olds in 1998 to 3.49 per 1,000 3-6 y olds in 2018, a 612% increase. However, diagnosed incidence rates did not rise uniformly across sociodemographic groups. By 2018, children of Black and Asian mothers were diagnosed at higher rates than children of non-Hispanic White mothers. Furthermore, among children of non-Hispanic White and Asian mothers, children of lower SES were diagnosed at higher rates than children of higher SES. These changes align with sociological theories of health disparities and contain important clues for more fully understanding the autism epidemic.
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Transtorno Autístico/diagnóstico , Transtorno Autístico/epidemiologia , California/epidemiologia , Criança , Pré-Escolar , Humanos , Incidência , PrevalênciaRESUMO
Differences in popularity are a key aspect of status in virtually all human groups and shape social interactions within them. Little is known, however, about how we track and neurally represent others' popularity. We addressed this question in two real-world social networks using sociometric methods to quantify popularity. Each group member (perceiver) viewed faces of every other group member (target) while whole-brain functional MRI data were collected. Independent functional localizer tasks were used to identify brain systems supporting affective valuation (ventromedial prefrontal cortex, ventral striatum, amygdala) and social cognition (dorsomedial prefrontal cortex, precuneus, temporoparietal junction), respectively. During the face-viewing task, activity in both types of neural systems tracked targets' sociometric popularity, even when controlling for potential confounds. The target popularity-social cognition system relationship was mediated by valuation system activity, suggesting that observing popular individuals elicits value signals that facilitate understanding their mental states. The target popularity-valuation system relationship was strongest for popular perceivers, suggesting enhanced sensitivity to differences among other group members' popularity. Popular group members also demonstrated greater interpersonal sensitivity by more accurately predicting how their own personalities were perceived by other individuals in the social network. These data offer insights into the mechanisms by which status guides social behavior.
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Encéfalo/fisiologia , Relações Interpessoais , Rede Social , Adulto , Cognição , Feminino , Humanos , Masculino , Comportamento Social , Percepção SocialRESUMO
This study reveals that the entry into World War I in 1917 indexed the decisive transition to the modern period in American political consciousness, ushering in new objects of political discourse, a more rapid pace of change of those objects, and a fundamental reframing of the main tasks of governance. We develop a strategy for identifying meaningful categories in textual corpora that span long historic durées, where terms, concepts, and language use changes. Our approach is able to account for the fluidity of discursive categories over time, and to analyze their continuity by identifying the discursive stream as the object of interest.
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Autism prevalence has increased rapidly in the United States during the past two decades. We have previously shown that the diffusion of information about autism through spatially proximate social relations has contributed significantly to the epidemic. This study expands on this finding by identifying the focal points for interaction that drive the proximity effect on subsequent diagnoses. We then consider how diffusion dynamics through interaction at critical focal points, in tandem with exogenous shocks, could have shaped the spatial dynamics of autism in California. We achieve these goals through an empirically calibrated simulation model of the whole population of 3- to 9-year-olds in California. We show that in the absence of interaction at these foci-principally malls and schools-we would not observe an autism epidemic. We also explore the idea that epigenetic changes affecting one generation in the distal past could shape the precise spatial patterns we observe among the next generation.
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OBJECTIVES: The goal of this study was to describe the typical, longitudinal, developmental trajectories of communication and social functioning in individuals with autism spectrum disorder from childhood through adulthood and to determine the correlates of these trajectories. METHODS: Children with autism spectrum disorder who were born in California from 1992 through 2016 and enrolled with the California Department of Developmental Services were identified. Subjects with <4 evaluations in the database were excluded, resulting in a sample of 71 285 individuals. Score sequences were constructed based on evaluative items for communication and social functioning. Typical trajectories were identified using group-based latent trajectory modeling, and logistic regression was used to determine the odds of classification into a social adolescent decline trajectory by individual-, family-, and zip code-level factors. RESULTS: Six typical patterns of communication functioning and 7 typical patterns of social functioning were identified. Whereas the majority of autistic individuals exhibit improved communication functioning as they age, the majority of individuals exhibit steady social functioning. A small group of individuals (5.0%) exhibits high social functioning in childhood that declines in adolescence. Membership in this adolescent decline group is associated with maternal non-Hispanic white race and ethnicity, female sex, moderate levels of maternal education, lower zip code-level median home values and population density, and higher zip code-level inequality. CONCLUSIONS: Most autistic individuals show improved communication and social functioning as they age, but not all do. Trajectory group membership is correlated with socioeconomic status. Future research should investigate what drives these correlations.
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Transtorno do Espectro Autista , Transtorno Autístico , Adolescente , Criança , Humanos , Feminino , Transtorno do Espectro Autista/diagnóstico , Comunicação , Bases de Dados Factuais , EscolaridadeRESUMO
Introduction: Cesarean section deliveries in the U.S. increased from 5% of births in 1970 to 32% in 2020. Little is known about trends in cesarean sections and inductions in low-risk pregnancies (i.e., those for which interventions would not be medically necessary). This study addresses the following questions: (1) what is the prevalence of elective deliveries at the population level?, (2) how has that changed over time?, and (3) to what extent do the rates of elective deliveries vary across the population? Methods: We first documented long-term trends in cesarean sections in the U.S., California, and New Jersey. We then used linked birth and hospital discharge records and an algorithm based on Joint Commission guidelines to identify low-risk pregnancies and document trends in cesarean sections and inductions in low-risk pregnancies in California and New Jersey over a recent 2-decade period, overall and by maternal characteristics and gestational age. Results: In low-risk pregnancies in California and New Jersey, rates of cesarean sections and inductions increased sharply from the early 1990s through the mid-2000s, peaked at 33% in California and 41% in New Jersey in 2007, and then declined somewhat, and the proportions of inductions that were followed by cesarean sections increased from fewer than 1 in 5 to about 1 in 4. More education, non-Hispanic White race/ethnicity, U.S.-born status, and non-Medicaid were associated with higher rates of interventions. Trends were similar across all socioeconomic groups, but differences have been narrowing in California. Among early-term (gestational age of 37-38 weeks) births in low-risk pregnancies, the rates of elective deliveries increased substantially in both states until the mid/late-2000s, peaked at about 35% in California and over 40% in New Jersey, and then decreased in both states to about 20%. Conclusions: Given established health risks of nonmedically necessary cesarean sections, that a nontrivial share of induced deliveries in low-risk pregnancies result in cesarean sections, and that interventions in low-risk pregnancies have not substantially declined since their peak in the mid-2000s, the trends documented in this paper suggest that sustained, even increased, public health attention is needed to address the still-too-high rates of cesarean sections and inductions in the U.S.
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INTRODUCTION: Cesarean section and induced deliveries have increased substantially in the U.S., coinciding with increases in autism spectrum disorder. Studies have documented associations between cesarean section deliveries and autism spectrum disorder but have not comprehensively accounted for medical risks. This study evaluates the extent to which cesarean section and induced deliveries are associated with autism spectrum disorder in low-risk births. METHODS: In this retrospective cohort study, California's birth records (1992-2012) were linked to hospital discharge records to identify low-risk births using a stringent algorithm based on Joint Commission guidelines. Autism spectrum disorder status was based on California Department of Developmental Service data. Logistic regression models were used to estimate associations between autism spectrum disorder and induced vaginal deliveries, cesarean section deliveries not following induction, and cesarean section deliveries following induction, with noninduced vaginal deliveries as the reference category. RESULTS: A total of 1,488,425 low-risk births took place in California from 1992 to 2012. The adjusted odds of autism spectrum disorder were 7% higher for induced vaginal deliveries (AOR=1.07, 95% CI=1.01, 1.14), 26% higher for cesarean section deliveries not following induction (AOR=1.26, 95% CI=1.19, 1.33), and 31% higher for cesarean section deliveries following induction (AOR=1.31, 95% CI=1.18, 1.45) than for noninduced vaginal deliveries. Lower gestational age and neonatal morbidities did not appear to be important underlying pathways. The associations were insensitive to alternative model specifications and across subpopulations. These results suggest that, in low-risk pregnancies, up to 10% of autism spectrum disorder cases are potentially preventable by avoiding cesarean section deliveries. CONCLUSIONS: After accounting for medical risks, elective deliveries-particularly cesarean section deliveries-were associated with a substantially increased risk of autism spectrum disorder.
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Transtorno do Espectro Autista , Transtorno Autístico , Transtorno do Espectro Autista/epidemiologia , Transtorno do Espectro Autista/etiologia , Cesárea/efeitos adversos , Parto Obstétrico/efeitos adversos , Parto Obstétrico/métodos , Feminino , Humanos , Recém-Nascido , Gravidez , Estudos RetrospectivosRESUMO
The prevalence of autism has increased precipitously-roughly 10-fold in the past 40 years-yet no one knows exactly what caused this dramatic rise. Using a large and representative dataset that spans the California birth cohorts from 1992 through 2000, we examine individual and community resources associated with the likelihood of an autism diagnosis over time. This allows us to identify key social factors that have contributed to increased autism prevalence. While individual-level factors, such as birth weight and parental education, have had a fairly constant effect on likelihood of diagnosis over time, we find that community-level resources drive increased prevalence. This study suggests that neighborhoods dynamically interact with the people living in them in different ways at different times to shape health outcomes. By treating neighborhoods as dynamic, we can better understand the changing socioeconomic gradient of autism and the increase in prevalence.
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This article engages with problems that are usually opaque: What trajectories do scientific debates assume, when does a scientific community consider a proposition to be a fact, and how can we know that? We develop a strategy for evaluating the state of scientific contestation on issues. The analysis builds from Latour's black box imagery, which we observe in scientific citation networks. We show that as consensus forms, the importance of internal divisions to the overall network structure declines. We consider substantive cases that are now considered facts, such as the carcinogenicity of smoking and the non-carcinogenicity of coffee. We then employ the same analysis to currently contested cases: the suspected carcinogenicity of cellular phones, and the relationship between vaccines and autism. Extracting meaning from the internal structure of scientific knowledge carves a niche for renewed sociological commentary on science, revealing a typology of trajectories that scientific propositions may experience en route to consensus.
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OBJECTIVES: We sought to estimate the risk for autism associated with maternal and paternal age across successive birth cohorts. METHODS: We linked birth records and autism diagnostic records from the California Department of Developmental Services for children born in California between 1992 and 2000 to calculate the risk associated with maternal and paternal age for each birth cohort as well as for the pooled data. RESULTS: The categorical risks associated with maternal age over 40 years ranged from a high of 1.84 (95% confidence interval [CI] = 1.37, 2.47) to a low of 1.27 (95% CI = 0.95, 1.69). The risk associated with paternal age ranged from 1.29 (95% CI = 1.03, 1.6) to 1.71 (95% CI = 1.41, 2.08). CONCLUSIONS: Pooling data across multiple birth cohorts inflates the risk associated with paternal age. Analyses that do not suffer from problems produced by pooling across birth cohorts demonstrated that advanced maternal age, rather than paternal age, may pose greater risk. Future research examining parental age as a risk factor must be careful to avoid the paradoxes that can arise from pooling data, particularly during periods of social demographic change.
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Transtorno Autístico/epidemiologia , Idade Materna , Idade Paterna , Adulto , California/epidemiologia , Estudos de Coortes , Feminino , Humanos , Masculino , Gravidez , Medição de Risco , Fatores de Risco , Fatores SexuaisRESUMO
The pharmaceutical industry spends roughly 15 billion dollars annually on detailing - providing gifts, information, samples, trips, honoraria and other inducements - to physicians in order to encourage them to prescribe their drugs. In response, several states in the United States adopted policies that restrict detailing. Some states banned gifts from pharmaceutical companies to doctors, other states simply required physicians to disclose the gifts they receive, while most states allowed unrestricted detailing. We exploit this geographic variation to examine the relationship between gift regulation and the diffusion of four newly marketed medications. Using a dataset that captures 189 million psychotropic prescriptions written between 2005 and 2009, we find that uptake of new costly medications was significantly lower in states with marketing regulation than in areas that allowed unrestricted pharmaceutical marketing. In states with gift bans, we observed reductions in market shares ranging from 39% to 83%. Policies banning or restricting gifts were associated with the largest reductions in uptake. Disclosure policies were associated with a significantly smaller reduction in prescribing than gift bans and gift restrictions. In states that ban gift-giving, peer influence substituted for pharmaceutical detailing when a relatively beneficial drug came to market and provided a less biased channel for physicians to learn about new medications. Our work suggests that policies banning or limiting gifts from pharmaceutical representatives to doctors are likely to be more effective than disclosure policies alone.
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Conflito de Interesses , Doações/ética , Padrões de Prática Médica/ética , Indústria Farmacêutica/ética , Humanos , Marketing , Médicos/psicologia , Políticas , Psicotrópicos/uso terapêutico , Estados UnidosRESUMO
BACKGROUND: Sibling sex ratios have been applied as an indirect test of a hypothesized association between prenatal testosterone levels and risk for autism, a developmental disorder disproportionately affecting males. Differences in sibling sex ratios between those with and without autism would provide evidence of a shared risk factor for autism and offspring sex. Conclusions related to prenatal testosterone, however, require additional assumptions. Here, we used directed acyclic graphs (DAGs) to clarify the elements required for a valid test of the hypothesis that sibling sex ratios differ between children with and without autism. We then conducted such a test using a large, population-based sample of children. METHODS: Over 1.1 million subjects, born in California from 1992-2007, and identified through birth records, were included. The association between autism diagnosis, determined using the administrative database of the California Department of Developmental Services, and the sex of the subsequent sibling was examined using generalized estimating equations. Sources of potential bias identified using DAGs were addressed. RESULTS: Among male children with autism, 52.2% of next-born siblings were brothers, versus 51.0% for unaffected males. For females with autism, 50.2% of following siblings were brothers versus 51.2% among control females. The relative risk of a subsequent male sibling associated with autism diagnosis was 1.02 (95% confidence interval: 0.99, 1.04). CONCLUSIONS: In a large, population-based sample we failed to find evidence suggesting an excess of brothers among children with autism while controlling for several threats to validity. This test cannot rule out a role of any given exposure, including prenatal testosterone, in either risk of autism or offspring sex ratio, but suggests against a common cause of both.
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Transtorno do Espectro Autista/etiologia , Efeitos Tardios da Exposição Pré-Natal/etiologia , Androgênios/sangue , Transtorno do Espectro Autista/sangue , Transtorno do Espectro Autista/epidemiologia , California/epidemiologia , Feminino , Humanos , Masculino , Gravidez , Efeitos Tardios da Exposição Pré-Natal/sangue , Efeitos Tardios da Exposição Pré-Natal/epidemiologia , Risco , Razão de Masculinidade , IrmãosRESUMO
CONTEXT: It is often argued that adolescents who become pregnant do not sufficiently appreciate the negative consequences, and that prevention programs should target participants' attitudes toward pregnancy. METHODS: Data from the first two waves of the National Longitudinal Study of Adolescent Health were used to examine whether 15-19-year-old females' attitudes toward pregnancy influence their contraceptive consistency and their risk of pregnancy. Characteristics and attitudes associated with pregnancy and contraceptive use were assessed using bivariate and multivariate analysis. RESULTS: Twenty percent of female adolescents were defined as having antipregnancy attitudes, 8% as having propregnancy attitudes and 14% as being ambivalent toward pregnancy; the remainder were considered to have mainstream attitudes. Among sexually experienced adolescents, having an attitude toward pregnancy was not associated with risk of pregnancy. However, those who were ambivalent about pregnancy had reduced odds of using contraceptives consistently and inconsistently rather than not practicing contraception at all (odds ratios, 0.5 and 0.4, respectively). Antipregnancy respondents did not differ from proprepregancy respondents in terms of their contraceptive consistency. However, having a positive attitude toward contraception was associated with increased likelihood of inconsistent and consistent contraceptive use compared with nonuse (1.6 and 2.1, respectively). CONCLUSIONS: Programs designed to prevent pregnancy need to give young women information about pregnancy and opportunities to discuss the topic so that they form opinions. Furthermore, programs should emphasize positive attitudes toward contraception, because effective contraceptive use is shaped by such attitudes and is strongly associated with reduction of pregnancy risk.
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Comportamento do Adolescente/psicologia , Comportamento Contraceptivo/psicologia , Conhecimentos, Atitudes e Prática em Saúde , Gravidez na Adolescência/psicologia , Comportamento Sexual/psicologia , Adolescente , Comportamento do Adolescente/etnologia , Adulto , Comportamento Contraceptivo/etnologia , Anticoncepcionais/uso terapêutico , Dispositivos Anticoncepcionais/estatística & dados numéricos , Feminino , Humanos , Entrevistas como Assunto , Modelos Logísticos , Estudos Longitudinais , Gravidez , Gravidez na Adolescência/etnologia , Gravidez na Adolescência/prevenção & controle , Comportamento Sexual/etnologia , Estados Unidos , Sexo sem Proteção/etnologia , Sexo sem Proteção/estatística & dados numéricosRESUMO
At stake in the May 2013 publication of the Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition (DSM-5), are billions of dollars in insurance payments and government resources, as well as the diagnoses and treatment of millions of patients. We argue that the most recent revision process has missed social determinants of mental health disorders and their diagnosis: environmental factors triggering biological responses that manifest themselves in behavior; differing cultural perceptions about what is normal and what is abnormal behavior; and institutional pressures related to such matters as insurance reimbursements, disability benefits, and pharmaceutical marketing. In addition, the experts charged with revising the DSM lack a systematic way to take population-level variations in diagnoses into account. To address these problems, we propose the creation of an independent research review body that would monitor variations in diagnostic patterns, inform future DSM revisions, identify needed changes in mental health policy and practice, and recommend new avenues of research. Drawing on the best available knowledge, the review body would make possible more precise and equitable psychiatric diagnoses and interventions.
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Manual Diagnóstico e Estatístico de Transtornos Mentais , Transtornos Mentais/diagnóstico , Melhoria de Qualidade , Comitês Consultivos , Indústria Farmacêutica , Política de Saúde , Humanos , Estudos Interdisciplinares , Transtornos Mentais/classificação , Transtornos Mentais/etiologia , Psicologia , Melhoria de Qualidade/organização & administração , Determinantes Sociais da Saúde/estatística & dados numéricos , Fatores SocioeconômicosRESUMO
OBJECTIVE: The goal of this study was to describe the typical longitudinal developmental trajectories of social and communication functioning in children with autism and to determine the correlates of these trajectories. METHODS: Children with autism who were born in California from 1992 through 2001 and enrolled with the California Department of Developmental Services were identified. Subjects with <4 evaluations present in the database were excluded, resulting in a sample of 6975 children aged 2 to 14 years. Score sequences were constructed based on 9 evaluative items for social, communication, and repetitive behavior functioning. Typical trajectories were identified by using group-based latent trajectory modeling, and multinomial logistic regression models were used to determine the odds of classification within each trajectory varied by individual and family-level factors. RESULTS: Six typical patterns of social, communication, and repetitive behavior functioning were identified. These trajectories displayed significant heterogeneity in developmental pathways, and children whose symptoms were least severe at first diagnosis tended to improve more rapidly than those severely affected. One group of â¼10% of children experienced rapid gains, moving from severely affected to high functioning. Socioeconomic factors were correlated with trajectory outcomes; children with non-Hispanic, white, well-educated mothers were more likely to be high functioning, and minority children with less-educated mothers or intellectual disabilities were very unlikely to experience rapid gains. CONCLUSIONS: Children with autism have heterogeneous developmental pathways. One group of children evidenced remarkable developmental change over time. Understanding what drives these outcomes is thus critical.
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Transtornos Globais do Desenvolvimento Infantil/diagnóstico , Comunicação , Deficiências do Desenvolvimento/diagnóstico , Inteligência , Comportamento Social , Comportamento Estereotipado , Adolescente , California , Criança , Transtornos Globais do Desenvolvimento Infantil/classificação , Transtornos Globais do Desenvolvimento Infantil/epidemiologia , Transtornos Globais do Desenvolvimento Infantil/psicologia , Pré-Escolar , Deficiências do Desenvolvimento/classificação , Deficiências do Desenvolvimento/epidemiologia , Deficiências do Desenvolvimento/psicologia , Feminino , Hispânico ou Latino/psicologia , Hispânico ou Latino/estatística & dados numéricos , Humanos , Estudos Longitudinais , Masculino , Modelos Estatísticos , Fatores Socioeconômicos , Estatística como Assunto , População Branca/psicologia , População Branca/estatística & dados numéricosRESUMO
BACKGROUND: The incidence and prevalence of autism have dramatically increased over the last 20 years. Decomposition of autism incidence rates into age, period and cohort effects disentangle underlying domains of causal factors linked to time trends. We estimate an age-period-cohort effect model for autism diagnostic incidence overall and by level of functioning. METHODS: Data are drawn from sequential cohorts of all 6 501 262 individuals born in California from 1992 to 2003. Autism diagnoses from 1994 to 2005 were ascertained from the California Department of Development Services Client Development and Evaluation Report. RESULTS: Compared with those born in 1992, each successively younger cohort has significantly higher odds of an autism diagnosis than the previous cohort, controlling for age and period effects. For example, individuals born in 2003 have 16.6 times the odds of an autism diagnosis compared with those born in 1992 [95% confidence interval (CI) 7.8-35.3]. The cohort effect observed in these data is stronger for high than for low-functioning children with an autism diagnosis. DISCUSSION: Autism incidence in California exhibits a robust and linear positive cohort effect that is stronger among high-functioning children with an autism diagnosis. This finding indicates that the primary drivers of the increases in autism diagnoses must be factors that: (i) have increased linearly year-to-year; (ii) aggregate in birth cohorts; and (iii) are stronger among children with higher levels of functioning.
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Transtorno Autístico/epidemiologia , Fatores Etários , California/epidemiologia , Criança , Pré-Escolar , Estudos de Coortes , Feminino , Humanos , Incidência , Lactente , Masculino , Modelos Estatísticos , Prevalência , Fatores de RiscoRESUMO
OBJECTIVE: To determine whether the interpregnancy interval (IPI) is associated with the risk of autism in subsequent births. METHODS: Pairs of first- and second-born singleton full siblings were identified from all California births that occurred from 1992 to 2002 using birth records, and autism diagnoses were identified by using linked records of the California Department of Developmental Services. IPI was calculated as the time interval between birth dates minus the gestational age of the second sibling. In the primary analysis, logistic regression models were used to determine whether odds of autism in second-born children varied according to IPI. To address potential confounding by unmeasured family-level factors, a case-sibling control analysis determined whether affected sibling (first versus second) varied with IPI. RESULTS: An inverse association between IPI and odds of autism among 662 730 second-born children was observed. In particular, IPIs of <12, 12 to 23, and 24 to 35 months were associated with odds ratios (95% confidence intervals) for autism of 3.39 (3.00-3.82), 1.86 (1.65-2.10), and 1.26 (1.10-1.45) relative to IPIs of ≥ 36 months. The association was not mediated by preterm birth or low birth weight and persisted across categories of sociodemographic characteristics, with some attenuation in the oldest and youngest parents. Second-born children were at increased risk of autism relative to their firstborn siblings only in pairs with short IPIs. CONCLUSIONS: These results suggest that children born after shorter intervals between pregnancies are at increased risk of developing autism; the highest risk was associated with pregnancies spaced <1 year apart.