Handedness and schizotypy in non-psychotic relatives of patients with schizophrenia

Abstract

Existing studies have found the relationship between handedness and schizotypy to be inconsistent, and had limited generalisability since only highly homogeneous groups have been investigated. This study aimed to examine the relation between handedness and the four schizotypal factors identified from a previous confirmatory factor analysis in a population of high familial loading for schizophrenia. Study participants consisted of non-psychotic first-degree relatives (850 parents and 334 siblings) of sib-pairs who were co-affected with schizophrenia. All participants were interviewed with the Diagnostic Interview for Genetic Studies, which contains a section of the modified Structured Interview for Schizotypy, and the Annett handedness questionnaire. Both categorical and continuous indicators for handedness were examined. Non-right-handed siblings of schizophrenia patients displayed more positive schizotypal features than their right-handed counterparts when the two-way Annett's handedness classification was adopted. No association was found when handedness was treated as continuous. The relationship between handedness and schizotypy was insignificant for parents probably due to the strong social pressure against left-handedness. We concluded that categorical non-right-handedness was associated with positive schizotypy in non-psychotic siblings of schizophrenia patients. The results indicate that an atypical cerebral lateralisation underlying non-right-handedness may be also a contributing factor to positive schizotypy.

Keywords:

• Positive schizotypy
• Handedness
• Familial loading
• Schizophrenia

Acknowledgements

Funding for this study was provided by grants from the National Health Research Institutes, Taiwan (DOH 88-HR-825; NHRI-GT-EX89P825P; NHRI- EX90-8825PP; NHRI- EX91, 92, 93-9113PP; NHRI-EX95, 96, 97, 98-9511PP) and National Science Council, Taiwan (NSC 96-2628-B-002-066-MY2 and NSC98-2314-B-002-125-MY3), US National Institute of Mental Health grant 1R01-MH-59624-01, and NTU grant 97HP0023 and 97HP0071.

The authors thank the administrative authority of the Taiwan Schizophrenia Linkage Study (TSLS) group for their support, including National Taoyuan, Chaotun, Yu-Li Psychiatric Center, National Cheng-Kung University Hospital, Kaohsiung Kai-Suan Psychiatric Hospital, Yu-Li Veteran Hospital, and Taipei City Psychiatric Center, and the participating psychiatrists of the TSLS group for helping with the ascertainment of the study participants. The authors also thank the participating psychiatrists of the Multidimensional Psychopathology Group Research Projects who helped in the recruitment and evaluation of schizophrenic patients.