Am J Psychiatry 1997; 154:39-46
Copyright © 1997 by American Psychiatric Association
Cognitive deficit measures in schizophrenia: factor structure and clinical correlates
F Lieh-Mak and PW Lee
Department of Psychiatry, University of Hong Kong, Pokfulam, Hong Kong.
OBJECTIVE: The authors aimed to delineate the "common denominators" across
a representative number of cognitive measures by administering such
measures to a large number of schizophrenic subjects. The authors also
aimed to study the consistency of the subjects' performance over a 1-year
period and to look into the relationship between cognitive task performance
and clinical status. METHOD: One hundred fifty-seven schizophrenic subjects
with a DSM-III-R diagnosis of schizophrenia were assessed under
standardized testing conditions on the dichotic listening and shadowing
task, the span of apprehension task, the simple reaction time tasks, the
critical stimulus duration, and the interstimulus interval in which they
would become free from the masking effect. The clinical status of the
subjects was assessed during index assessment, and 97 subjects were
reassessed at the end of 1 year. Forty- seven subjects were randomly
selected for reassessment on the cognitive tasks administered 1 year
earlier. The subjects' performance was compared to that of 56
nonschizophrenic patients with nasopharyngeal carcinoma who had undergone
radiation therapy. RESULTS: The cognitive task scores were factor analyzed,
giving five distinct factors made up of the span of apprehension accuracy
scores, simple reaction time scores, shadowing accuracy scores, span of
apprehension error scores, and susceptibility to interference scores. At
index assessment, the subjects' shadowing accuracy and reaction time were
significantly related to their quality of life, social adjustment, and
positive symptoms. The subjects' span of apprehension scores were related
to their negative symptoms, measured in terms of work and daily life
functions. The initial relationship between the subjects' cognitive test
scores and their outcome status remained consistent at follow-up.
CONCLUSIONS: The documented cognitive deficits in schizophrenic patients
probably reflect a more enduring trait-like status with correlations with
outcome status. These results also indicate that the cognitive measures may
be simplified in complexity without a corresponding reduction in their
clinical significance.
