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Laterality phenotypes in patients with schizophrenia, their siblings and controls: associations with clinical and cognitive variables

Centre for Clinical Research in Neuropsychiatry and School of Psychiatry and Clinical Neurosciences, University of Western Australia, Claremont, Western Australia

Geoff Hammond, PhD

School of Psychology, University of Western Australia, Claremont, Western Australia

Johanna C. Badcock, PhD and Assen Jablensky, MD, DMSc, FRCPsych, FRANZCP

Centre for Clinical Research in Neuropsychiatry and School of Psychiatry and Clinical Neurosciences, University of Western Australia, Claremont, Western Australia

Correspondence: Dr Milan Dragovic, Centre for Clinical Research in Neuropsychiatry, Private Mail Bag No. 1, Claremont, WA 6910, Australia. E-mail: milan{at}ccrn.uwa.edu.au

Declaration of interest None.

Background Various behavioural indices of brain lateralisation significantly intercorrelate, but current research in this area still focuses on single behavioural asymmetries, such as handedness.

Aims To describe a novel approach, which simultaneously integrates various lateralityindices and delineates complex phenotypes.

Method Grade of membership analysis was used to describe latent, complex lateralisation phenotypes in patients with schizophrenia (n=157), theirsiblings (n=74) and controls (n=77). The indices used were asymmetries of eye, foot and hand; hand motor proficiency; and handedness of patient’s first-degree relatives.

Results Three distinct pure types of lateralisation (‘right’, ‘left’ and ‘mixed’) were evident in patients compared with two (‘right’ and ‘left’) in siblings and controls. The ‘mixed’ type in patients featured absence of eye and foot lateralisation and presence of familial sinistrality, despite a right-hand dominance for writing. Patients with schizophrenia expressing the ‘left’ phenotype had a more severe course of illness, significantly increased scores ontwo schizotypy factors and poorer neurocognitive performance. The pure types in the siblings were similar to those in healthy controls.

Conclusions The findings suggest that a leftward reversal, rather than a reduction in lateralisation, is associated with clinical severity and neurocognitive deficits in patients with schizophrenia.