IQ trajectories in autistic children through preadolescence
Marjorie Solomon1,2,3, Billy Cho1,3, Ana-Maria Iosif4
1Department of Psychiatry & Behavioral Sciences, University of California-Davis, Sacramento, CA, 2230 Stockton Blvd., Sacramento, CA 95817.
Insights
Autistic children show consistent intellectual development patterns, with some improving significantly while others maintain intellectual disability. Early communication and behavior predict long-term IQ trajectories.
Area of Science:
- Neuroscience
- Developmental Psychology
- Child Psychiatry
Background:
- Longitudinal study of intellectual development in autistic individuals.
- Followed 373 autistic children from early childhood to preadolescence.
- Utilized data from the Autism Phenome Project cohort.
Purpose of the Study:
- Identify distinct intellectual quotient (IQ) trajectory subgroups in autistic youth.
- Analyze developmental courses and predictors of trajectory membership.
- Understand the long-term intellectual development patterns in autism.
Main Methods:
- Multivariate latent class growth analysis to identify IQ trajectory subgroups.
- Linear mixed effects models for group differences and developmental courses.
- Multinomial logistic regression to assess predictors of trajectory membership.
Main Results:
- Three distinct IQ trajectories identified: persistent intellectual disability (45%), substantial IQ increases (39%), and persistently high IQ (16%).
- No significant differences in autism severity or communication scores by preadolescence.
- Early communication gains and reduced externalizing behaviors predicted better IQ trajectories.
Conclusions:
- Autistic youth exhibit stable IQ developmental trajectories from early childhood to preadolescence.
- Prognostic factors for trajectory membership may inform targeted interventions.
- Focus on improving adaptive communication and managing externalizing symptoms is crucial.
Background:
We extended our study of trajectories of intellectual development of autistic individuals in early (mean age 3 years; T1), and middle childhood (mean age 5 years, 7 months; T2) into later middle childhood/preadolescence (mean age 11 years, 6 months; T3) in the longitudinal Autism Phenome Project cohort. Participants included 373 autistic children (115 females).
Methods:
Multivariate latent class growth analysis was used to identify distinct IQ trajectory subgroups. Baseline and developmental course group differences and predictors of trajectory membership were assessed using linear mixed effects models with repeated measures with pairwise testing, multinomial logistic regression models, and sensitivity analyses.
Results:
We isolated three IQ trajectories between T1 and T3 for autistic youth that were similar to those found in our prior work. These included a group with persistent intellectual disability (ID; 45%), a group with substantial increases in IQ (CHG; 39%), and a group with persistently average or above IQs (P-High; 16%). By T3, the groups did not differ in ADOS-2 calibrated severity scores (CSS), and there were no group differences between Vineland (VABS) communication scores in CHG and P-High. T1-T3 externalizing behaviors declined significantly for CHG, however, there were no significant T3 group differences between internalizing or externalizing symptoms. T1 correlates for CHG and P-High versus ID group membership included higher VABS communication and lower ADOS-2 CSS. A T1 to T2 increase in VABS communication scores and a decline in externalizing predicted CHG versus ID group membership at T3, while T1 to T2 improvement in VABS communication and reduction in ADOS-2 CSS predicted P-High versus ID group membership.
Conclusions:
Autistic youth exhibit consistent IQ developmental trajectories from early childhood through preadolescence. Factors associated with trajectory group membership may provide clues about prognosis, and the need for treatments that improve adaptive communication and externalizing symptoms.
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