The Causal Relationships Among Neurocognition, Social Cognition and Functional Outcome in Schizophrenia: Implications for Heterogeneity and Assessment

Background and Purpose. Longitudinal data on critical variables in schizophrenia can shed light on different aspects of heterogeneity as well on as the causal relationships among variables presumed to underlay multi-dimensional outcome. Accurate assessment is essential to individualized treatment planning, and meaningful assessment is based on accurate causal models. Understanding the causal relationships among therapeutic predictors and treatment outcomes leads us to better ways of integrating individual strengths into effective treatment plans. Neurocognition and social cognition are increasingly being recognized as variables that predict functional outcome and responsiveness to rehabilitation in schizophrenia. Up to now there have been no investigations of how these variables are causally related. Statistical methods such as cross-lagged panel analyses in the context of longitudinal designs have been advocated as ways to test causal assumptions about the relationships among variables. In the present study, we aimed to examine the possible causal relationships among neurocognition, social cognition, and functional outcome over a 12 month period.

Methods. Data were gathered on 130 individuals diagnosed with schizophrenia recruited upon admission to community-based psychosocial rehabilitation who were followed over a 12 month period. Psychosocial functioning data were gathered at baseline, 6 and 12 months on the Role Functioning Scale measuring work, social, and independent living functioning. Tests of neurocognition and social cognition were administered at baseline and 12 months by testers blind to the psychosocial data. Neurocognition was measured with five indicators reflecting verbal fluency, working memory, episodic memory, sustained attention, and mental flexibility. Social cognition was the sum of three scales measuring visual and auditory perception of six basic emotions (happy, angry, afraid, sad, surprised and ashamed). Data were analyzed using latent difference score models in structural equation modeling. Latent difference score models are a form of cross-lagged panel analysis using latent change constructs.

Results. The results of latent difference score models testing the possible causal relationships among neurocognition, social cognition and functional outcome showed the following. Baseline neurocognition was strongly related to change in social cognition over 12 months, while baseline social cognition was not related to change in neurocognition over 12 months. Baseline neurocognition was strongly related to change in functional outcome over 12 months, while baseline functional outcome was not related to change in neurocognition over 12 months. Baseline social cognition was related to change in functional outcome over 12 months, while baseline functional outcome was not related to change in social cognition over 12 months.

Conclusion and Implications. Findings support the following causal model: neurocognition is causally prior to social cognition, and both neurocognition and social cognition are causally prior to functional outcome. This causal understanding is critical to accurate assessment of functional aspects of schizophrenia, and has implications for treatment and for specifying underlying models of heterogeneity in schizophrenia. These are the first findings to empirically establish the causal ordering of these variables in a longitudinal context. Based on our findings, we suggest that clinicians pay attention to emotional and cognitive capacities in adults with schizophrenia in assessing clients' potential for community functioning improvements.