Preschoolers with ASD Who Have Both Cognitive and Adaptive Functioning Delays: Follow-up to Age Eight
Objectives: To examine developmental trajectories of children with ASD who have combined cognitive and adaptive delays at age 2-4. Specifically: (1) how do mean cognitive and adaptive scores change from age 2-4 to age 6, and to age 8 and (2), how frequently do delays (scores < 70) persist to ages 6 and 8?
Methods: Participants were 70 children from the Pathways in ASD cohort (76% boys; 33% of larger sample), recruited from one of five Canadian cities. At diagnosis, each child had both cognitive and adaptive standard scores < 70. Children were initially assessed at mean age 41.31 (SD= 7.96) months and reassessed at 79.15 (SD= 3.92) months and 104.71 (SD= 2.83) months. Adaptive functioning was measured using the Vineland Adaptive Behavior Scales, 2nd edition. Cognitive functioning was measured using either the Merrill-Palmer Revised (M-P-R), Wechsler Preschool and Primary Scale of Intelligence- 3rd edition (WPPSI-III) or Wechsler Intelligence Scale for Children- 4th edition (WISC-IV).
Results: (1) Between age 2-4 and age 6, mean IQ increased by 13 points (from 29.30 to 42.77, p <.001) and mean adaptive functioning increased by 4 points (from 62.31 to 65.87, p = .007). Smaller gains took place between ages 6 and 8: 6-point gain in IQ, to 48.55 (p = .003); 2-point gain in adaptive functioning, to 67.94 (p = .001). 2) At age 6, only 57% of children continued to have delays in both cognitive and adaptive functioning (see Table). In contrast, stability of skill level (combined delay vs. no combined delay) between ages 6 and 8 was high (ĸ = .86). At age 8, 56% had combined delays.
Conclusions: Results are consistent with clinical guidelines that suggest caution in interpreting low cognitive and adaptive scores in very young children with ASD, as scores and skill levels often improve by age 6. Stability of skill level is high between ages 6 and 8. It is also important to ensure that a diagnosis of ASD does not overshadow potential diagnosis of intellectual disability. Mean cognitive and adaptive scores remained < 70 at age 8, and over 50% of children continued to have significant impairment in both areas. During the preschool years, discussing the possibility of later intellectual disability may be appropriate. Re-assessment is important for this subgroup of children with ASD.