WHAT'S KNOWN ON THIS SUBJECT: Autism is widely considered a heterogeneous disorder in terms of etiology and phenotype. Although autism is usually a lifelong disorder, little is known about the rate or timing of how children develop regarding their communication and social functioning. WHAT THIS STUDY ADDS:Utilizing annual evaluations for a large population of children with autism, we describe the 6 most common trajectories from diagnosis through age 14 years. Trajectories revealed considerable variation, and high socioeconomic status children were more likely to experience rapid improvement.abstract 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 ∼10% 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.

Background-The incidence of autism rose dramatically between 1992 and 2001, while the age at which children were first diagnosed declined. During this period the size and composition of the autism caseload has changed, but little is known about whether the factors associated with the timing of diagnosis may also have shifted. Using a multilevel analysis strategy, the individual and community-level factors associated with age of diagnosis were modelled across 10 birth cohorts of California children.

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.

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.