Stability and course of neuropsychological deficits in schizophrenia

Background: Neuropsychological deficits in schizophrenia appear to predate clinical symptoms of the disease and become more pronounced at illness onse t, but controversy exists about whether and when further neuropsychological progression may occur. Objective: To identify and characterize any subset of patients who evidence d progressive neuropsychological impairment, we compared the longitudinal s tability of neuropsychological functioning in schizophrenic outpatients and normal comparison subjects. Methods: One hundred forty-two schizophrenic outpatients and 206 normal com parison subjects were given annually scheduled comprehensive neuropsycholog ical evaluations during an average of 3 years (range, 6 months to 10 years) . Clinically and demographically defined subgroups were compared, and test- retest norms were used to identify individual patients who showed unusual w orsening over time. Results: The schizophrenic group was neuropsychologically more impaired tha n the normal comparison subjects but showed comparable test-retest reliabil ity and comparable neuropsychological stability over both short (mean, 1.6 years) and long (mean, 5 years) follow-up periods. No significant differenc es in neuropsychological change were found between schizophrenic subgroups defined by current age, age at onset of illness, baseline level of neuropsy chological impairment, improvement or worsening of clinical symptoms, and o ccurrence of incident tardive dyskinesia. Norms for change also failed to s how neuropsychological progression in individuals with schizophrenia. Conclusions: Neuropsychological impairment in ambulatory persons with schiz ophrenia appears to remain stable, regardless of baseline characteristics a nd changes in clinical state. Our results may not be generalizable to the m inority of institutionalized poor-outcome patients.