Dr Gerasimos Chatzidamianos Ph.D. (Cantab), MPhil. (Cantab), BSc (Hons)
Spectrum Centre for Mental Health Research
Division of Health Research, Faculty of Health and Medicine
Lancaster University, Lancaster, U.K.,
Schizophrenia is known to occur in prelingually profoundly Deaf individuals with probably the same frequency as in the hearing population. However, the impact of Deafness on the clinical features of schizophrenia is an under-researched area. The current thesis aims to provide the first comprehensive analysis of the ways schizophrenia manifests itself in Deaf adults, with particular reference to language disorders.
Two studies were performed. Study 1 empirically tested a clinical observation that motor dexterity for sign was preserved despite there being impairment in motor skill for purposes other than language in schizophrenia. 15 profoundly Deaf sign-using schizophrenic patients and 28 matched profoundly Deaf healthy volunteers were given specially devised measures for motor skill in linguistic and non-linguistic tasks. The study supported the hypothesis that there is a dissociation between relatively preserved motor skill for sign language and impaired motor skill for non-linguistic gestural tasks. This study also produced an incidental observation: the Deaf schizophrenic patients appeared to make frequent errors in handshape, which in the context of the study implied abnormality in production of a particular linguistic element of sign language, classifiers.
The aim in Study 2 was to further examine Study 1’s finding of abnormality in the production of handshapes in classifier construction, specifically to replicate it under controlled conditions and establish whether it is more pronounced than in other aspects of language. The performance of a second group of 14 profoundly Deaf signing schizophrenic patients and 35 Deaf healthy volunteers was recorded based on a battery of measures testing classifier and noun comprehension and production. This confirmed Study 1’s finding of errors in classifier production in Deaf schizophrenic patients and provided qualified support for the hypothesis that the impairment was more marked for production than comprehension, and more marked for classifiers than for nouns.
Taking the results of the analyses of both studies together, the present thesis suggests that motor abnormalities are present in Deaf schizophrenia in the face of relatively intact motor skill for language. Despite its motor intactness, however, certain aspects of sign language in Deaf schizophrenia seem to be disproportionately affected than others (e.g. nouns). This primarily applies to the production of handshape in classifier construction. Conversely, Deaf people with schizophrenia appear to produce lexicalised responses at a comparable rate with that of their Deaf healthy counterparts. These results suggest that schizophrenia affects language production in Deaf patients with schizophrenia in unique ways.
Clinical implications
Being an under-research area, understanding how differently schizophrenia manifests itself in the Deaf population is critical. Whilst the prevalence of schizophrenia in the Deaf is similar to that of the hearing population, Deaf people are over-represented in psychiatric services. The underlying reasons are complicated, but it becomes apparent that the varied expression of schizophrenia, coupled with the idiosyncratic language proficiency as found in Deaf people increases the level of difficulty in diagnosing the condition. This is particularly relevant in the case of Deaf people as most clinician are unfamiliar with Deafness, sign language and the implication of growing up in a hearing world without access to appropriate education, information or services.
The present results put forward the idea that clinicians should expect language production to be motorically fine. If severe motor symptoms present, clinicians should investigate possible extrapyramidal side effects from the medication or the potential comorbidity with other neurological disorders. Despite its motor intactness, however, sign language production appears disproportionately impaired when compared to sign comprehension. That means that Deaf people with schizophrenia are able to understand sign sufficiently, but fail to produce it to a relatively similar degree. This is not to say that their linguistic output is incomprehensible similar to dysphasia, for example. In effect, Deaf people with schizophrenia should have no problem understand their clinicians in sign language. The marked but subtle impairment in production (especially in classifier constructions), however, increases the challenges in identifying symptoms such as formal thought disorder (i.e. incoherence of speech/sign). Given that lexicalisation of sign appears intact, clinicians should be mindful of these challenges and adjust their signing accordingly.
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