Hand Preference in Stuttering: Meta-Analyses

Abstract

Reduced hemispheric asymmetries, as well as their behavioral manifestation in the form of atypical handedness (i.e., non-right, left-, or mixed-handedness), are linked to neurodevelopmental disorders, such as autism spectrum disorder, and several psychiatric disorders, such as schizophrenia. One neurodevelopmental disorder that is associated with reduced hemispheric asymmetries, but for which findings on behavioral laterality are conflicting, is stuttering. Here, we report a series of meta-analyses of studies that report handedness (assessed as hand preference) levels in individuals who stutter (otherwise healthy) compared to controls. For this purpose, articles were identified via a search in PubMed, Scopus, and PsycInfo (13 June 2023). On the basis of k = 52 identified studies totaling n = 2590 individuals who stutter and n = 17,148 controls, five random effects meta-analyses were conducted: four using the odds ratio [left-handers (forced choice); left-handers (extreme); mixed-handers; non-right-handers vs. total)] and one using the standardized difference in means as the effect size. We did not find evidence of a left (extreme)- or mixed-handedness difference or a difference in mean handedness scores, but evidence did emerge, when it came to left-handedness (forced-choice) and (inconclusively for) non-right-handedness. Risk-of-bias analysis was not deemed necessary in the context of these meta-analyses. Differences in hand skill or strength of handedness could not be assessed as no pertinent studies were located. Severity of stuttering could not be used s a moderator, as too few studies broke down their data according to severity. Our findings do not allow for firm conclusions to be drawn on whether stuttering is associated with reduced hemispheric asymmetries, at least when it comes to their behavioral manifestation.

Behavioral lateralization in bipolar disorders: a systematic review

“…Similar to depression, BD is a heterogenous disorder with one subgroup marked by neurodevelopmental aspects with earlier age at onset (Cross-Disorder Group of the Psychiatric Genomics Consortium 2019 ). Indeed, studies on handedness in neurodevelopmental disorders report higher rates of non-right-handedness in attention deficit hyperactivity disorder (Nastou et al 2022 ), autism spectrum disorders (Markou et al 2017 ), stuttering (Papadatou-Pastou et al 2023 ) and dyslexia (Packheiser et al 2023 ), reinforcing the role of neurodevelopmental aspects in non-right-handedness. Given the hypothesis of a chronological component, age of onset may be a relevant factor for detecting atypical asymmetries.…”