Purpose: This study aimed to evaluate the association of positive and negative symptoms, as well as of neurocognition to functional status in patients with schizophrenia. Participants were 309 veterans with DSM-IV-diagnosed schizophrenia or schizoaffective disorder who were enrolled in a 12-month double-blind clinical trial and randomized to receive either 5 to 20 mg/d of oral olanzapine or haloperidol. Patients were assessed at study entry and at 3, 6 and 12-months on the PANSS and measures of verbal memory, verbal fluency, fine motor coordination, visual sequencing/set shifting, and conceptual reasoning. Functional status was evaluated by the Heinrichs-Carpenter Quality of Life Scale (QLS) and by days of employment in the past 30. Hierarchical regression models examined the association of functional status with symptomatology and three neurocognitive factors (motor skills, memory and card sorting), controlling for demographics and visit number. A mixed effects model was used to adjust for repeated observations from the same subjects.
Results: The PANSS explained 16% additional variance in QLS total score after accounting for demographics and visit number (p<.001), while the neurocognitive factors explained only 4% additional variance beyond the effect of symptoms. When neurocognition was entered before symptoms, it explained an additional 8% of the variance on the QLS total score, while the PANSS explained an additional 12% over and above neurocognition.
Conclusions: These findings suggest that symptoms may pose an equal or greater impediment to functional capacity independent of neurocognition, at least in younger non-institutionalized people with schizophrenia.