Background
Strong daily living skills (DLS) are associated with positive outcomes. Prior studies have documented intellectual quotient (IQ)-DLS discrepancies in autistic individuals with average or higher cognitive abilities. Little work in this area includes individuals with co-occurring intellectual disability (ID) or examines IQ-DLS discrepancies at the level of DLS subdomains (i.e., Personal, Domestic, and Community skills). This study examined trajectories of IQ-DLS discrepancies from ages 2–25 in autistic individuals with ID.
Methods
A total of 127 individuals from a well-characterized longitudinal cohort with verbal IQ < 70 at age 9 were included. IQ-DLS discrepancy scores were calculated by subtracting DLS AEs from nonverbal mental age (NVMA) estimates. Group-based trajectory modeling identified IQ-DLS discrepancy trajectory groups for the DLS domain and Personal, Domestic, and Community subdomains. One-way ANOVA and chi-square analyses were used to compare trajectory groups on demographic and phenotypic characteristics.
Results
Two DLS domain discrepancy trajectory groups emerged: IQ > DLS (cognitive abilities exceeded DLS) and IQ < DLS (DLS exceeded cognitive abilities); most participants (78%) were in the IQ > DLS group. An additional group, IQ = DLS (cognitive abilities and DLS were commensurate), emerged in each of the DLS subdomains, for a total of three trajectory groups. Within DLS subdomains, approximately 80% of participants were in either the IQ = DLS or the IQ < DLS trajectory group. In other words, examining scores at the DLS domain-level indicated most participants had cognitive abilities that exceeded DLS, but subdomain scores indicated most participants had DLS that equaled or exceeded cognitive abilities.
Conclusions
These results challenge the notion that autism is usually associated with weaknesses in DLS compared to IQ. At the subdomain level, 80% of participants had DLS commensurate with or stronger than their cognitive abilities, indicating domain-level scores may obscure important variability in daily functioning. This work highlights the importance of including autistic individuals with ID in research; patterns observed in samples without ID may not be generalizable.