The cognitive dysfunction regularly seen in schizophrenia patients may be associated with negative symptoms and medication-induced extrapyramidal symptoms, show study findings.
The findings published in Psychiatry and Clinical Neurosciences suggest that minimizing the incidence of these symptoms may be an important strategy to improve cognitive dysfunction, according to Tsunehiko Tanaka (Shiga University of Medical Science, Otsu, Japan) and colleagues.
"Based on reports that cognitive dysfunction is associated with lowered social function and quality of life, treatment for improving cognitive dysfunction will be a fundamental requirement," say the researchers.
Tanaka et al evaluated cognitive function in 61 stabilized schizophrenia outpatients with mild psychotic symptoms using the Brief Assessment of Cognition in Schizophrenia (BACS). This revealed Z-scores of -1.23 for working memory, -1.81 for motor speed, -1.66 for attention and speed of information processing, -0.82 for verbal fluency, and -1.20 for executive function.
The researchers say the identified Z-score range suggests that "even symptomatically stabilized outpatients who are able to live in the community have prominent cognitive dysfunction."
Analysis of correlations between the BACS and clinical symptom scales revealed that the Total Positive and Negative Syndrome Scale (PANSS) score significantly correlated with verbal memory, attention and speed of information processing, as well as composite score.
Furthermore, PANSS Negative syndrome score significantly correlated with verbal memory, working memory, attention and speed of information processing, verbal fluency, and composite score. According to Tanaka and team, this moderate correlation shows that cognitive dysfunction is more strongly related to negative symptoms than previous studies have reported.
A significant negative correlation was seen for the Drug-Induced Extrapyramidal Symptoms Scale (DIEPSS) score in relation to the PANSS attention and speed of information processing and composite score, despite the DIEPSS score being very low, at 1.6. The researchers say this finding suggests that even relatively mild extrapyramidal symptoms associated with antipsychotics can lead to poor cognitive performance.
"Efforts should be made to minimize drug-induced extrapyramidal symptoms in daily practice in order to improve cognitive dysfunction of schizophrenia patients," say the authors.
Cognitive dysfunction was shown to be independent of age, illness duration, medication, positive symptoms, general psychopathology, and depressive symptoms.
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