Structural and Functional Neurobiological Correlates of Functional Outcome in Schizophrenia: A Systematic Review

Background: Individuals with schizophrenia are burdened with impairments in functional outcome that have only been marginally rehabilitated with pharmacological and psychosocial interventions. This is most likely related to the significant gap between brain imaging and functional outcomes studies, which are rarely considered together. The biopsychosocial lens of social work provides an opportunity to improve the lives of clients by bridging the gap between neuroscience and social work research on functional outcomes. Therefore, through the integration of neuroscience and social work, an original systematic review was conducted of all the existing peer-reviewed studies examining the neural correlates of functional outcome in individuals with schizophrenia. This research is critical to the development of social work interventions that aim to improve social and community functioning in individuals with this condition.

Method: A total of 27 (17 structural and 10 functional) brain imaging studies examining the structural and functional neurobiological underpinnings of functional outcomes in individuals with schizophrenia were extracted from literature searches in relevant databases occurring between 1968 and 2014. Extracted data included study characteristics [e.g., sample size (N), type of sample (first-episode or chronic schizophrenia), average age, the percent of males, mean illness duration, the design of the study (cross-sectional or longitudinal), the domain of functional outcome assessed, the measure used to assess functional outcome, and the task used during scanning for functional studies] and relevant relationship statistics. All correlations were normalized such that higher scores on functional outcome measures reflected improved functioning.  

Results: Frontal-limbic regional themes were observed in both the structural and functional studies, which were partially predictive of functional outcome. Smaller lateral ventricles (all r < -.58, all p < .05) and greater brain volumes (all r < .63, all p < .05) in the superior frontal cortex, dorsolateral prefrontal cortex (DLPFC) and hippocampal regions were indicative of better functional outcomes in schizophrenia. Greater activation (all r < .59, all p < .05) in the medial prefrontal cortex (MPFC), DLPFC, and amygdala, as well as lower activation in the occipital cortex (r = -.40, p <.05) during cognitive loading were also related to better functional outcomes in this condition. Relationships ranged from small to medium in size, indicating clear biomarkers that contribute to, but do not solely determine functional outcomes.

Conclusions: The structure and function of frontal and limbic brain regions may be important neurobiological links to functional outcomes in individuals with schizophrenia and may serve as treatment biomarkers. With the biopsychosocial perspective of social work, evidence for brain-functional outcome relationships in individuals with schizophrenia has important implications for the development of interventions targeted at facilitating a more optimal functional recovery in people living with this condition.