Writing Development in Higher-Functioning Children with Autism Spectrum Disorder with and without ADHD Comorbidity

Background: Higher-functioning children with ASD (HFASD) often experience difficulty with writing. However, this problem also occurs for children with ADHD. Few studies have examined the effect of the co-occurrence of symptoms of ASD and ADHD on writing, and few studies have addressed the question of how well children with HFASD develop writing abilities across time in longitudinal research.

Objectives: To address these gaps in the literature, this longitudinal study examined writing ability in 8–16 year-old school-age children with HFASD compared to children with ADHD and typical development (TD). This study also examined the hypothesis that children with HFASD with comorbid elevations of ADHD would display poorer writing development than children with HFASD without comorbid ADHD.

Methods: The participants were 17 children with HFASD without ADHD symptoms (HFASD-L), 39 with HFASD and ADHD symptoms (HFASD-H), 24 children with only ADHD symptoms, and 25 children with TD. ASD symptoms were confirmed with the ADOS–2. ADHD symptoms (T-scores > 70) were confirmed with parent reports on the Conners-3. All groups were age matched at the first visit (T1) and re-assessed 15 months later (T2). IQ was assessed with the WASI-II, and FIQ was included as a covariate in all analyses due to group differences (Table 1). Writing was assessed with the Wechsler Individual Achievement Test–3 (WIAT-III). At T1, all children handwrote their responses; at T2, children were given the choice (their preference) to handwrite or type their responses.

Results: A mixed-design MANCOVA yielded a significant effect for time point on overall writing scores for all groups, F(1,100)=7.0, p=.009, eta²=.07. Significant time point effects across groups were also observed on the WIAT-III word count and thematic content scores (p=.027 and .009, respectively; see Figure 1). Main effects for diagnostic group were observed for overall writing score, F(3,100)=3.14, p=.03, and word count, F(3,100)=3.38, p=.03, both eta²=.09 (see Figure 1), but not for thematic content, p=.15. Children with HFASD-H performed poorest of all groups for overall writing score and word count (see Figure 1) but planned comparison revealed this difference was significant only versus the children with TD. Children with HFASD-H also performed poorly on thematic content at T1, but this effect was not apparent at T2 (see Figure 1).

Conclusions: This study provided evidence that many children with HFASD may be at risk for poor academic writing development, especially children with HFASD and comorbid ADHD symptoms. It was not clear if the writing risk of children with HFASD-H was appreciably greater than children with HFASD-L or ADHD; sample sizes may have limited the power of these comparisons. Alternatively, the results also provided evidence of improvement in writing across groups, suggesting that specific writing instruction may be a useful modality for communication intervention among children with HFASD or ADHD. Future research on measurement issues, such as handwriting versus typing and comparing the WIAT-III versus other writing assessments, will sharpen our understanding of writing development in children with HFASD and ADHD.