Cognitive Impairment and Substance Abuse History as Predictors of the Temporal Stability of Negative Symptoms in Schizophrenia

Research has not consistently indicated that negative symptoms in schizophrenia are temporally stable. One possible explanation for this is that stable negative symptoms are a characteristic of only some individuals with schizophrenia. The current study explored whether cognitive impairment and stimulant abuse history were associated with amount of change in negative symptom level over a 1-year period. Results indicated that among 72 subjects with schizophrenia, performance on the Wisconsin Card Sorting Test and history of stimulant abuse significantly accounted for 18% of the variance in symptom variability after age, intelligence quotient, and initial symptom severity were controlled. As hypothesized, poorer performance on the Wisconsin Carding Sorting Test was associated with less symptom variability, whereas a more extensive stimulant abuse history was associated with greater variability. A discriminant function analysis was able to correctly classify 96% of subjects as having stable symptoms but only 30% as having unstable symptoms indicating a sensitive, but not specific, classification. This finding suggests that cognitive deficits may be a necessary but insufficient condition for temporal stability of negative symptoms and that negative symptoms in schizophrenia are a complex phenomenon best understood in the context of other features of illness and psychosocial variables.