BPRS symptom factors and sleep variables in schizophrenia.

To examine the relationship of clinical symptoms to sleep architecture, polysomnography and clinical ratings were carried out in 20 male psychiatric in-patients who met Research Diagnostic Criteria for schizophrenia. Clinical symptoms were assessed by the Brief Psychiatric Rating Scale (BPRS). Four BPRS sub-factors, i.e., 'Thinking Disturbance', 'Withdrawal/Retardation', 'Hostility/Suspiciousness', and 'Anxiety/Depression' were correlated with five components of sleep architecture, namely, sleep onset latency, total sleep time, total slow wave sleep minutes (the summation of visually scored stages 3 and 4), total REM minutes, and REM latency. Partial correlations were computed to control for the effects of age. Of the 20 correlation coefficients computed, only one was statistically significant after Bonferroni correction, namely, sleep onset latency was positively correlated with the 'Thinking Disturbance' factor. This finding is consistent with studies showing that psychotic exacerbation is associated with reduced sleep efficiency. In contrast to this cross-sectional design, longitudinal studies are more likely to clarify the relationship of sleep architecture to changes in clinical state.