Over a 10-year period, patients with schizophrenia and other psychoses had a cognitive decline in memory, verbal learning, and vocabulary according to a study published in the American Journal of Psychiatry.
Researchers assessed baseline cognitive function using data obtained from the Aetiology and Ethnicity in Schizophrenia and Other Psychoses study of first-episode psychosis. Follow-up neuropsychological assessments were performed on 106 of these patients with a diagnosis of schizophrenia (n=65) or other psychoses (n=41). The average follow-up duration was 109.3 months (SD 29.5) for patients and 102.9 months (SD 34.1) for controls. Cognitive decline was assessed by subtracting follow-up from baseline assessments. Data were analyzed using analysis of covariance models with planned orthogonal comparisons.
Patients with schizophrenia had cognitive impairment at both initial and follow-up diagnoses. A small, but significantly larger decline in intelligence quotient was measured in schizophrenic patients after approximately 10-year follow-up (effect=-0.28; 95% CI, -0.47 to -0.09; P =.003). Other psychoses did not show significant decline in intelligence quotient (effect=-0.09; 95% CI, -0.30 to 0.11; P =.37).
In terms of cognitive function, memory declined to a greater extent in schizophrenic patients when compared with the comparison group. Specific functions, including verbal learning (P =.001), immediate recall, delayed recall, and vocabulary (P =.003) were reduced. Verbal learning was found to decline with other psychoses as well. There was no decline in processing speed, executive function, working memory, or visual-spatial ability over time when compared with comparison participants in both schizophrenic and other psychoses groups.
Treatment with first-generation vs both first- and second-generation antipsychotics did not affect intelligence quotient decline, nor did treatment duration. No association was found between initial symptom severity and change in cognitive function.
This study had several limitations, including the sample size, which made subanalysis of psychoses not possible. Additionally, the fixed follow-up time point did not allow for a detailed study of the time-course for cognitive decline. Potential confounding contributors to cognitive decline, such as smoking, drug use, victimization, physical health problems, and education after initial follow-up were not controlled for.
In conclusion, after an approximately 10-year period, the researchers found a small but significant decline in the intelligence quotient of patients with schizophrenia. Interestingly, cognitive decline was not global, but found to target verbal knowledge and memory. Other psychoses demonstrated cognitive decline but were more limited in scope. This study helps clarify the effects of schizophrenia on long-term cognitive function.
Multiple authors declared associations with the pharmaceutical industry. Please see original reference for a full list of authors’ disclosures.
Zanelli J, Mollon J, Sandin S, et al. Cognitive change in schizophrenia and other psychoses in the decade following the first episode [published online July 1, 2019]. Am J Psychiatry. doi: 10.1176/appi.ajp.2019.18091088