Autism 30 Years Later: A Follow up Study of Children Diagnosed with ASD from 1970-1999

Background: While there is a developing literature on ASD in adulthood, few longitudinal studies from childhood to adulthood have been conducted. The majority of these studies have focused on the transition years from adolescence to young adulthood. Thus, there is little research on autism in middle adulthood.

Objectives: This research capitalizes on a unique data set of individuals who were diagnosed with ASD as children by the University of North Carolina TEACCH Autism Program from 1970-1999. Participants were reevaluated an average of 30 years after their initial diagnosis in order characterize changes in symptom severity, IQ, and adaptive behavior from childhood to mid-adulthood. Specific objectives included: (1) Measure the stability of ASD characteristics from childhood into middle adulthood; (2) Measure the relative increase or decrease in ASD characteristics from childhood into mid-adulthood.

Methods: Participants were 55 adults with ASD in mid-adulthood (27-57 years of age, M = 37 years) who had previously participated in a larger study of adult outcomes. All adults were diagnosed with an ASD during childhood (initial evaluations at 29 months to 16 years, M=6 years, 4 months). Participants participated in comprehensive assessments in adulthood including diagnostic (ADOS-2 and CARS-2), intellectual functioning (Stanford-Binet-5), and adaptive behavior (VABS-II) assessments. Additionally, childhood assessment data were also used from the CARS, IQ scores from a wide variety of tests, and Vineland Adaptive Behavior Scale (VABS).

Results: 54 out of 55 adults met diagnostic criteria across clinical judgment, CARS-2 and ADOS-2. CARS-2 scores during adulthood were modestly related to childhood CARS scores (r=+.34, p=.01), with little overall change in total CARS score (Childhood M=33.5, Adulthood M=33.1; t(54)=.45, p=.66). Intellectual functioning was remarkably stable across 30 years with adult IQ being strongly correlated to childhood IQ (r=+.71, p<.001). However, IQ scores showed a marginally significant drop over time (Childhood M=71.4, Adulthood M=66.9; t(52)=1.65, p=.10). Adaptive behavior was also quite stable across 30 years with adult VABS-II Standard Scores being strongly correlated to childhood VABS Standard Scores (r=+.52, p<.001). However, these scores showed a substantial decrease over time (Childhood M=61.1, Adulthood M=45.2; t(49)=5.29, p<.001).

Conclusions: In spite of a 30-year delay, ASD diagnoses were stable over time. Of the 55 participants in this study, only 1 did not receive a current ASD diagnosis. ASD symptoms, intellectual functioning, and adaptive behavior during adulthood were highly correlated with scores from childhood. This is especially impressive given the wide variety of IQ tests given during the childhood assessments. Both intellectual functioning and adaptive behavior showed decreased scores in adulthood indicating a decreased rate of development compared to the normative sample. This decrease was especially large for adaptive behavior indicating that adaptive behavior is a crucial area where individuals with ASD are at great risk to fall even further behind their peers as they move into adulthood. These adaptive behavior skills ought to be a primary target for interventions with children and adults with ASD as research suggests that adaptive behavior is the primary predictor of adult employment and quality of life.