A joint occurrence of atypical behavioral lateralization and schizophrenia: coincidental or causative?

The association between atypical lateralization of hand preferences (still a stigmatized behavioral trait in some cultures) with schizophrenia has been studied over the four last decades, repeatedly showing an increased incidence of atypical lateralization of hand dominance in this population. However, no final verdict on the causal direction between these two phenomena has been given. Atypical hand preferences, at the phenotypic level, have been subject to diverse classifications – commonly as left-handedness, but increasingly often as ‘non-right-handedness’, a ‘pooled handedness’ category made of two more homogeneous classes, and finally ‘left- and mixed-handedness’. Research has identified many associations of atypical lateralization of hand preferences with structural and functional brain asymmetries, cognitive performance, and clinical features in the population of schizophrenia patients. In this article, we critically appraise this work and suggest that both complex phenotypes, atypical lateralization of hand dominance and schizophrenia, most likely have common neurodevelopmental and genetic origin