Primary negative symptoms adversely affect social, vocational and recreational functioning in patients with schizophrenia, even when the potential influence of secondary negative symptoms has been accounted for, Canadian researchers report.
Although the negative symptoms of schizophrenia have consistently been linked to poor functional outcome, distinguishing between primary idiopathic and secondary non-idiopathic negative symptoms is “an important clinical issue,” say Gagan Fervaha and colleagues from the University of Toronto, in Ontario. This is because “the underlying pathophysiology and therefore potential treatments differ for each of these”, they explain.
In their study of 1427 individuals with schizophrenia (mean age 40.6 years, 74% men), the researchers found that negative symptoms – assessed with the Positive and Negative Syndrome Scale, the Calgary Depression Scale for Schizophrenia and the Simpson-Angus scale for extrapyramidal side effects – were significantly associated with functional status, as assessed by the Heinrichs-Carpenter Quality of Life Scale.
Indeed, as negative symptom burden increased, function within the domains interpersonal relations (social), instrumental role (vocational) and use of common objects and activities (recreational) significantly decreased.
When the researchers looked at secondary influences on negative symptom burden, they found that negative symptom severity increased significantly with increasing severity of psychosis, depression, anxiety and extrapyramidal symptoms.
However, accounting for these secondary symptoms in statistical analyses did not attenuate the relationship between primary negative symptoms and functional outcome, nor did excluding patients with moderate-severe psychosis, depression, anxiety and/or extrapyramidal symptoms.
The relationship between primary negative symptoms and each functional outcome domain also remained significant when the researchers only included patients with mild secondary symptoms who reported being antipsychotic free for at least 2 weeks prior to entering the study (n=56).
Writing in European Psychiatry, Fervaha and co-authors highlight that negative symptoms explained a large degree of variance in functional status, particularly for social and recreational functioning where the variance accounted for by negative symptoms alone was greater than that for psychosis, depression, anxiety and extrapyramidal symptoms together.
“As the negative symptoms of schizophrenia are increasingly being embraced as multidimensional, with certain facets (e.g., amotivation/apathy) demonstrating greater impact on functional outcomes, it will be an important area of research to discern potential secondary sources of negative symptoms that differentially affect one domain of negative symptoms over another”, says the team.
“Furthermore, it will also be important to examine whether specific primary negative symptoms (e.g., blunted affect) influence functional outcomes after other possible variables have been controlled for.”
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