Academic journal article Hong Kong Journal of Psychiatry

Language Disorganisation in Schizophrenia: Validation and Assessment with a New Clinical Rating Instrument

Academic journal article Hong Kong Journal of Psychiatry

Language Disorganisation in Schizophrenia: Validation and Assessment with a New Clinical Rating Instrument

Article excerpt

SUMMARY

Existing rating scales for formal thought disorder do not fully take into consideration levels of language organisation as suggested by modem linguistics science. A new scale, the Clinical Language Disorder Rating Scale (CLANG), is proposed using a framework based upon linguistically meaningful levels of organisation. The scale was validated in an extensive sample of 204 Hong Kong Chinese schizophrenic patients. Good interrater and internal reliabilities were obtained. Factor analysis revealed three major domains of language disorder captured by the scale: the semantic level, the syntactic level, and the production level. Satisfactory convergent and criterion validity were established by comparing CLANG subscale scores with ratings based on other standard instruments. We conclude that CLANG is a reliable, valid and informative instrument for clinical assessment of language disorder in schizophrenia.

Keywords: formal thought disorder, language, schizophrenia, rating instrument, validation.

INTRODUCTION

Formal thought disorder (language disorganisation) is an important sign in schizophrenia, Compared to other psychotic symptoms (such as hallucination and delusions), language disorganization could be directly observed and is not dependent upon subjective report of abnormal experiences on the part of the patient. Consequently language disorganization can be regarded as one of the more informative clinical marker of brain dysfunction in psychosis (Taylor et al 1994). Another impetus for the study of language disorganisation has been the delineation of a disorganization syndrome in schizophrenia (in which language dysfunction is a major component) which is independent of positive and negative symptoms (Sell et al 1994; Bassett et al 1994; Thompson & Meltzer, 1993; Malta et al 1993; Peralta et al 1992). Recent neuroimaging studies have provided preliminary evidence for specific neurobiological correlates of the disorganisation syndrome (Liddle et al 1992; Rossi et al 1994; Shenton et al 1992).

Evaluation of language disorder in psychiatry has not been a trivial task. Many approaches have evolved in the past decades. They could be divided into two board categories: firstly, detailed post hoc analysis of language output (e.g. complexity of sentence structure, relative frequencies of adjectives and qualifying clauses etc.) (Manschreck et al 1991; King et al 1990; Morice, 1986; Fraser et al, 1986; Morice & McNicol, 1985 & 1986; Morice & Igram, 1983); and secondly, real-time ratings based on clinician judgment (Simpson & Davis, 1985). The former is time consuming and objective rating is mostly confined to the level of syntax (grammar) analysis. Clinician-rated scales have the additional advantage of full access to all levels of contextual information.

However, existing clinician-rated scales for formal thought disorder suffer from a variety of shortcomings. For example, the Thought, Language and Communication disorder rating scale (TLC) (Andreasen & Grove, 1986; Andreasen, 1979a & 1979b) adopted and re-defined some relatively dated psychopathological terms and does not take into full consideration recent advances in the understanding of language organization. There is consequently need for a new and relatively simple rating instrument which is based on a modem psycholinguistic framework.

Studies in psycholinguistics over the last few decades have suggested several different levels of language organization. At each level basic units interact with one another and operate within a distinct set of rules unique to the level. For example, words are constructed from phonemes (basic units of speech sound) based on particular rules (not all permutations of letters and phonemes are legal). At the level of syntax, sentences are constructed from words and clauses according to grammatical rules. Semantics addresses how meanings are conveyed by words or clauses. …

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