Do positive symptom and negative symptom subtypes of schizophrenia show qualitative differences in language production?

Abstract

The present study examined a prominent symptom subtype conception of the psychopathology of schizophrenia. It analysed the presumed dichotomy between hallucinations, delusions and formal thought disorder as positive symptoms and flattening of affect and poverty of speech as negative symptoms, and tested predictions concerning the nature of the mediating processes of positive and negative symptoms. Four different analyses were applied to the transcripts of speech produced by 9 normals, 10 chronic schizophrenics with only positive symptoms of whom 7 had incoherence of speech, and 9 chronic schizophrenics with only negative symptoms of whom 4 had poverty of speech. The conception of the nature of the mediating processes of positive and negative symptoms was not supported by the results. Further, a clear dichotomy between positive and negative symptom groups was not shown to exist, because positive speech disorder and negative speech disorder did not follow the presupposed dichotomy. Thus, contrary to existing conceptions of speech disorder in schizophrenia, both positive and negative speech disorder are marked by poverty of thought, as measured by the production of fewer and shorter ideas and lower speech variability.