IQ trajectories in autistic children through preadolescence

Abstract

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 for repeated measures with pairwise testing, multinomial logistic regression models, and sensitivity analyses. Results We isolated three IQ trajectory groups 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, 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.

Intellectual development in young children with autism spectrum disorders: A longitudinal study

“…They found that PIQ and VIQ showed comparable development for almost 75% of the participating children, while approximately one‐quarter showed decline. In a follow‐up study that tested intellectual development in autism from early childhood through preadolescence, Solomon et al (2023) found that a considerable number of the autistic participants (almost 40%) improved in IQ for at least 1 standard deviation from early childhood through age 12.…”

Profiles of minimally verbal autistic children: Illuminating the neglected end of the spectrum

“…When developmental trajectories are examined, this subgroup of those with co‐occurring delays and/or limited verbal communication tends to have a stable or worsening trajectory across time. (Georgiades et al, 2013; Pickles et al, 2020; Solomon et al, 2023; Szatmari et al, 2015; Waizbard‐Bartov et al, 2022). Some groups have described samples of exclusively minimally verbal autistic individuals within a single domain (Bal et al, 2016; Chang et al, 2018; Frost et al, 2017; Harrop et al, 2021).…”