Handedness in ADHD: Meta-Analyses

Abstract

Meta-analyses have shown that several neurodevelopmental and psychiatric disorders, such as autism spectrum disorder and schizophrenia, are associated with a higher prevalence of left- and/or mixed-handedness. One neurodevelopmental disorder for which this association is unclear is attention deficit hyperactivity disorder (ADHD). Here, some empirical studies have found evidence for a higher prevalence of left- and/or mixed-handedness in individuals with ADHD compared to neurotypical individuals. However, other studies failed to establish such an association. Therefore, meta-analytic integration is critical to estimate whether or not there is an association between handedness and ADHD. We report the results of three meta-analyses comparing handedness in individuals with ADHD to controls (typically developing individuals). The results show no evidence of differences in left-handedness and non-right-handedness between individuals with ADHD and controls. It was, however, found that individuals with ADHD showed a higher prevalence of mixed-handedness than controls. These findings are discussed in the context of the hypothesis that ADHD is a disorder in which mostly right-hemispheric brain networks are affected. Since right-handedness represents a dominance of the left motor cortex for fine motor behavior, such as writing, as well as a left-hemispheric dominance for language functions, and about 90% of individuals are right-handers, this hypothesis might explain why left-handedness is mostly unaffected in ADHD. We suggest that only in conditions where language is affected one should expect to find elevated levels of left-handedness.

Phenotyping in clinical laterality research: a comparison of commonly used methods to determine mixed-handedness and ambidexterity

“…This is specifically problematic as mixedhandedness has repeatedly been associated with neurodevelopmental and mental disorders. More precisely, meta-analyses confirmed increased rates of mixedhandedness in autism spectrum disorder (Markou et al, 2017), attentiondeficit/hyperactivity disorder (Nastou et al, 2022), dyslexia (Packheiser et al, 2023), posttraumatic stress disorder (Borawski et al, 2022;Goetz et al, 2016) and schizophrenia (Mallet et al, 2022;Sommer et al, 2001). For example, one large cohort study found an increased prevalence of 34.1% for mixed-handedness in subjects diagnosed with schizophrenia (best estimate of the prevalence of mixed-handedness in the general population based on meta-analysis: 9.33%, Papadatou-Pastou et al (2020)) that was further associated with increased positive symptoms and a current depressive episode (Mallet et al, 2022).…”

Handedness in Twins: Meta-Analyses

“…Moreover, they can investigate possible small study bias in the literature and importantly allow for moderator analyses to investigate variables that could moderate the prevalence of handedness categories among twins (Maxwell, Lau, & Howard, 2015). Indeed, the vast field of handedness has recently seen an upsurge of meta-analyses that aim to summarize the literature and provide estimates of atypical handedness in various populations (e.g., individuals with autism (Markou, Ahtam, & Papadatou-Pastou, 2017), deaf individuals (Papadatou-Pastou & Sáfár, 2016), intellectually disabled and intellectually gifted individuals (Papadatou-Pastou & Tomprou, 2015), individuals with ADHD (Nastou, Ocklenburg, & Papadatou-Pastou, 2020)). Sicotte et al (1999) do report a meta-analysis of the handedness literature in twins.…”