The primary purpose of the present study is to examine the relationship between handedness and schizophrenia. I will approach the question by using meta-analytical techniques; testing the hypothesis that mixed-handedness is more frequent among schizophrenic patients then healthy subjects (controls). Firstly, background information within the frames of schizophrenia and handedness will be reported. Secondly, the restrictions of the current study will be described in the subsections of study selection, search strategy, data extraction and data analyses in the methods section. Thereafter, in the results section the meta-analytical findings will be revealed. Lastly, in the discussion section, the results will be interpreted and analysed.
The current definition of schizophrenia according to the American Psychiatric Association (2000), DSM-IV-TR, is that it is a chronic incapacitating sickness characterized by the bizarre changes in cognition, behaviour and affect. Some common typical symptoms are bizarre delusions and behaviours, hallucinations (generally auditory) and disorganised speech. Based on the symptoms present, schizophrenic patients may be labelled into one of many subtypes, which is the paranoid, catatonic, hebephrenic (“disorganized”) and simple subtypes. If the patient does not fit into any subtype, then the patient will be characterized as having “undifferentiated” schizophrenia.
An important focus in the study of schizophrenia has been the abnormal lateralization; since, cerebral asymmetries reflect normal developmental processes (Crow, T.J., Colter, N., Frith, CD., Johnstone, E.C. & Owens, D.G.C., 1989) there have been lesser anatomical and functional asymmetries in patients with schizophrenic symptoms than in the general population (Crow, T.J., 1997). It has been suggested that the relationship between
References: American Psychiatric Association. (2000). Diagnostic and statistical manual of mental disorders (4th ed., text revision). Washington, DC: American Psychiatric Association. American Psychiatric Association. (1987). Diagnostic and statistical manual of mental disorders (3rd ed., revision). Washington, DC: American Psychiatric Association. American Psychiatric Association. (1980). Diagnostic and statistical manual of mental disorders (3rd ed.). Washington, DC: American Psychiatric Association. Cannon, M. Byrne, M., Cassidy, B., Larkin, C., Horgan, R., Sheppard, N.P. & O’Callaghan, E. (1995). Prevalence and correlates of mixed-handedness in schizophrenia. Psychiatry Research, 59, 119-125. Crow, T.J. (1997). Schizophrenia as failure of hemispheric dominance for language. Trends Neuroscience. 20(8): 339-43. Crow, T.J., Colter, N., Frith, CD., Johnstone, E.C Malesu, R.R., Cannon, M., Jones, P.B., McKenzie, K., Gilvarry, K., Rifkin, L., Toone, B.K. & Murray, R.M. (1996). Mixed-Handedness in Patients with Functional Psychosis. British Journal of Psychiatry, 168, 234-236. Orr, K.G.D., Cannon, M., Gilvarry, C.M., Jones P.B. & Murray, R.M. (1999). Schizophrenic patients and their first-degree relatives show an excess of mixed-handedness. Schizophrenia Research, 39, 167–176. Sommer, I., Ramsey, N., Kahn, R., Aleman, A. & Bouma, A. (2001). Handedness, language lateralisation and anatomical asymmetry in schizophrenia: meta-analysis. Brithish Journal of Psychiatry, 178, 344-51.