Clinical and cognitive factors associated with verbal memory task performance in patients with schizophrenia

Objective: The authors have previously shown the role of depression, slowin g of processing speed, and selective attention deficit in verbal memory tas k performance in schizophrenia. They wished to determine the specific contr ibution of each of these factors to various types of memory impairment. Method: The negative symptom score from the Positive and Negative Syndrome Scale, the Hamilton Depression Rating Scale score, a measure of processing speed, and a measure of selective attention were entered as predictors in r egression analyses. Furthermore, analyses of covariance were conducted on t he memory measures to test the significance of the differences between schi zophrenic patients and healthy comparison subjects after control for proces sing speed and selective attention. Results: Depression was associated only with deep encoding reflected by sem antic clustering. Selective attention was associated only with superficial encoding reflected by serial recall. Slowing of processing speed was associ ated with both deep and superficial encoding. Negative symptoms were not as sociated with memory impairment except for the avolition item from the Scal e for the Assessment of Negative Symptoms. Processing speed accounted for a ll the group differences on the memory measures that reflected superficial encoding. In addition, a subgroup of patients with no or minor depression w as not significantly impaired on deep encoding relative to the healthy comp arison group. Conclusions: The authors suggest that verbal memory impairment in schizo ph renia is a consequence of depression and slowness, rather than a primary fe ature of the disease.