Specificity of Handwriting Impairments in Children with Autism Spectrum Disorder

Background: Handwriting impairments have long been recognized as being common in autism.  Numerous studies have revealed difficulties with motor function in children with autism spectrum disorder (ASD) (e.g., Manjiviona et al., 1995; Ghaziuddin et al., 1998; Noterdaeme et al., 2002; Jansiewicz et al., 2006; Mostofsky et al., 2006); however, none included a detailed analysis of handwriting until very recently when we reported that, compared to typically developing (TD) children, children with ASD showed significant difficulty with handwriting (Fuentes et al., 2009). Our findings revealed that children with ASD had particular difficulty with letter formation, but not in their ability to correctly size, align, or space their letters.  Whether this pattern of findings is specific to ASD remains unclear.  In separate studies, handwriting impairments have been observed in children with Attention Deficit Hyperactivity Disorder (ADHD); these children show particular difficulty with writing legibly and with correctly aligning and spacing letters (Tucha & Lange, 2001).  There have been no studies, however, directly comparing handwriting in children with ASD and ADHD.

Objectives: To examine the specificity of handwriting impairments in children with ASD by comparing their performance to children with ADHD as well as TD children.

Methods: Nine children with ASD (mean age 10.35; 3 females), 7 children with ADHD (mean age 10.00; 3 females), and 10 TD children (mean age 10.89; 4 females) completed the Minnesota Handwriting Assessment (MHA) (Reisman et al., 1999); the groups were matched on age, gender, handedness and IQ.  Subjects were instructed to use their best handwriting to copy the following words exactly on the provided test sheet:  “The brown jumped lazy fox quick dogs over”.  Each letter was scored individually according to the Minnesota Handwriting Assessment scoring protocol on five categories:  Legibility, Form, Alignment, Size and Spacing.

Results: A 3-way MANOVA revealed a significant effect of diagnosis for form (p=0.02), alignment (p=0.05) and total (p=0.03) scores.  Further 2-way analyses revealed that children with ASD demonstrated significantly worse form (F=7.36, p=0.02) and total score (F=7.98, p=0.01) than TD children.  In comparison, children with ADHD demonstrated significant handwriting impairments in legibility (F=6.47, p=0.02), form (F=7.81, p=0.01) and alignment (F=10.01, p=0.01).  Comparisons of ASD and ADHD children revealed no significant differences on legibility, form, alignment, size or spacing.

Conclusions: Children with ASD demonstrated an overall impairment in handwriting, specifically seen in the quality of letter formation.  In contrast, children with ADHD showed a broader range of impairments, which included difficulties with legibility, form and alignment.  The findings suggest that for children with ASD, difficulty with handwriting may be associated with abnormalities in the internal representation of how the letters are formed and/or how those representations are executed.  In contrast, handwriting difficulty in children with ADHD appears to be associated with a broader range of difficulties, in particular problems with motor control necessary for proper alignment and legibility.