Autism symptoms in children with attention-deficit/hyperactivity disorder: a community-based study

Background Attention-Deficit/Hyperactivity Disorder (ADHD) is the most common neurodevelopmental disorder in children (Polanczyk, Willcutt, Salum, Kieling, & Rohde, 2014) and is highly comorbid with Autism Spectrum Disorder (ASD) (Green et al., 2015; Kotte et al., 2013). Although it is well established that children with ADHD or ASD and their families experience poorer functioning including child and parent mental health problems, child peer problems, poorer family quality of life (FQoL) and parenting difficulties, it is unknown how comorbid ASD symptoms contribute to child and family functioning in children with ADHD. It is important to understand which comorbidities contribute to poorer child and family functioning to guide treatment planning. Aims This study aimed to examine the prevalence of ASD symptoms in children with ADHD and the association between ASD symptoms and child and family functioning across three connected studies. The specific aims of each study are outlined below. Study 1. To examine the prevalence and type of ASD symptoms (social interaction, communication and stereotyped behaviour) in children with ADHD and non-ADHD controls. Within the ADHD group only, we also examined the relationship between ADHD subtype, hyperactive/impulsive and inattentive symptoms, ADHD symptom severity and child gender and ASD symptom severity. Study 2. To examine the association between ASD symptoms and (a) social functioning; (b) mental health; (c) quality of life and (d) sleep, in children with and without ADHD. Study 3. To examine the association between ASD symptoms (measured dimensionally) in children with and without ADHD and a broad range of family functioning variables and to examine differences between ADHD+ASD, ADHD and control groups on family functioning variables. Methods Participants were 6-10 year old children (164 ADHD; 198 non-ADHD control) attending 43 schools in Melbourne, Australia, who were participating in the Children’s Attention Project. ADHD was assessed in two stages using the parent and teacher Conners’ 3 ADHD index and the Diagnostic Interview Schedule for Children IV (DISC-IV). ASD symptoms were identified using the Social Communication Questionnaire (SCQ). Child functioning measures were social functioning (Strengths and Difficulties Questionnaire (SDQ), mental health (DISC-IV, SDQ), quality of life (QoL: Pediatric Quality of Life Inventory 4.0) and sleep problem severity. Family functioning outcome variables were parent mental health, family quality of life (FQoL), and scales assessing couple conflict, couple support and parenting behaviours. Unadjusted and adjusted linear and logistic regression examined continuous and categorical outcomes, respectively. Results Study 1. Children with ADHD had more ASD symptoms than non-ADHD controls (adjusted mean difference = 4.0, 95% confidence interval (CI) 2.8; 5.3, p < 0.001, effect size = 0.7). Boys with ADHD had greater ASD symptom severity than girls with ADHD (adjusted mean difference = 2.9, 95% CI 0.8; 5.2, p = 0.01, effect size = 0.4). Greater ADHD symptom severity was associated with greater ASD symptom severity (regression co-efficient = 1.6, 95% CI 1.2; 2.0, p < 0.001). No differences were observed by ADHD subtype. Greater hyperactive/impulsive symptoms were associated with greater ASD symptoms (regression coefficient = 1.0; 95% CI 0.0; 2.0, p = 0.04) however, this finding attenuated in adjusted analyses, which accounted for parent educational attainment, socioeconomic status, child internalising and externalising comorbidities (p = 0.45). Study 2. Each standard deviation (SD) increase in SCQ scores was associated with a 6.7 unit reduction in QoL (p < 0.001) and greater parent and teacher-reported peer problems, emotional and conduct problems. For every SD increase in SCQ scores, internalising (OR = 1.8, 95% CI 1.3, 2.6, p = 0.001) and externalising disorders (OR = 1.5, 95% CI 1.1, 2.1, p = 0.02) increased, as did moderate/severe sleep problems (OR = 1.5, 95% CI 1.0, 2.2, p = 0.04). Most findings held in analyses adjusting for socio-demographic factors, ADHD symptom severity, and comorbidities (when not the outcome), with the exception of externalising disorders and sleep problems. Study 3. In unadjusted dimensional analyses, higher ASD symptoms were associated with more couple conflict (p = 0.04) and poorer FQoL for all subscales (p ≤ 0.001), with non-significant trends for less couple support (R2 = 0.10, p = 0.06), more hostile parenting (R2 = 0.02, p = 0.06) and poorer parent mental health (R2 = 0.02, p = 0.07). In adjusted dimensional analyses, higher ASD symptoms were only associated with poorer FQoL, across all subscales only (p ≤ 0.01). The trend association between ASD symptoms and parent mental health attenuated due to meaningful associations with comorbid internalising disorder (p = 0.003) and ADHD symptom severity (p = 0.05). The trend association between ASD symptoms and hostile parenting attenuated due to significant associations with comorbid externalising disorders (p = 0.002), lower parent education attainment (p = 0.03) and greater ADHD symptom severity (p = 0.04). Less couple support attenuated due to a significant association with socioeconomic status (p = 0.004). In unadjusted categorical analyses, parents of children with ADHD+ASD reported more couple conflict (p = 0.04), less couple support (p = 0.001), poorer FQoL (p <0.001) and a non-significant trend for greater mental health difficulties (p = 0.07), compared to the ADHD group. In adjusted categorical analyses, parents of children with ADHD+ASD had poorer parent self-efficacy (p = 0.02), poorer FQoL (p < 0.05) (p < 0.05) and a non-significant trend for less couple support (p = 0.06), compared to parents of children with ADHD. In unadjusted categorical analyses, family functioning was significantly poorer for the ADHD and ADHD+ASD groups, compared to controls for most outcomes (p