Neurobiology of schizophrenia: search for the elusive correlation with symptoms

Abstract

In the last half-century, human neuroscience methods provided a way to study schizophrenia in vivo, and established that it is associated with subtle abnormalities in brain structure and function. However, efforts to understand the neurobiological bases of the clinical symptoms that the diagnosis is based on have been largely unsuccessful. In this paper, we provide an overview of the conceptual and methodological obstacles that undermine efforts to link the severity of specific symptoms to specific neurobiological measures. These obstacles include small samples, questionable reliability and validity of measurements, medication confounds, failure to distinguish state and trait effects, correlation-causation ambiguity, and the absence of compelling animal models of specific symptoms to test mechanistic hypotheses derived from brain-symptom correlations. We conclude with recommendations to promote progress in establishing brain-symptom relationships.

Keywords: correlation; negative symptoms; neurobiology; positive symptoms; rating scales; reliability; schizophrenia; validity.

Figure 1

This figure shows the 95% confidence intervals for two Pearson product-moment correlation coefficient values, r = 0.25 and r = 0.75, as a function of sample size. Note the wide confidence intervals when correlations are based on small sample sizes, particularly when n < 50 subjects.