Simple Executive Function as an endophenotype of autism-ADHD, and differing associations between simple versus complex Executive Functions and autism/ADHD traits

Executive Functions (EFs) enable us to control attention and behaviour in pursuit of a goal. In this longitudinal study, 107 children with a family history of autism and/or ADHD (FH-autism/ADHD), and 24 children with no FH-autism/ADHD completed a battery of EF tasks (5 tasks at age 2 years, 7 tasks at age 3 years). Parents reported on their child’s autism- (Q-CHAT at age 2, SRS-2 at age 3), and ADHD-related traits (CBCL DSM-ADHD scale at both ages). The FH-autism/ADHD group showed lower scores on simple EFs (involving inhibiting a response, and holding in mind) at ages 2 and 3. Sub-group analyses indicated lower Executive Attention (top-down attentional control) scores for the FH-autism group aged 2, and lower Complex EF (involving selectively deploying responses, or updating information) scores for the FH-autism-and-ADHD group aged 3. Three-year-olds’ Simple EF factor scores were negatively associated with ADHD-related traits but not autism traits, whilst Complex EF factor scores were negatively associated with autism traits (before correcting for multiple comparisons). Toddlers with a family history of autism and/or ADHD may benefit from interventions to support simple EF development, whilst those already showing autistic traits may additionally benefit from support with more-complex EF skills.