(The following work has recently been published, and may be found here.)
Schizophrenia patients demonstrate substantial neurocognitive impairment, deficits that have consistently been shown to contribute to their poor functional outcome. However, subsequent research in schizophrenia proposes a more complicated relationship, such that neurocognition and functioning may be mediated by social cognition. Social cognition is a multi-dimensional construct which encompasses several mental processes underlying social behavior, such as emotion recognition, social perception, theory of mind, social knowledge, and causal attribution style. Furthermore, mediation is a theoretical model that attempts to explain the process of how or why a cause-effect relationship occurs, proposing that the independent variable influences a mediator variable, which in turn influences the dependent variable. Alternatively, neurocognition, which generally predicts functioning in schizophrenia, does so partially through underlying substrates related to social cognitive processes.
Bipolar disorder patients also present with neurocognitive dysfunction, which may also predict worse functional outcome, disability, and psychosocial functioning, though not always. While social cognition appears to partially mediate the relationship between neurocognition and community functioning in schizophrenia, it is unknown whether and in what manner social cognition impacts this same association in bipolar disorder. Therefore, we assessed whether social cognition modulates the influence of neurocognition on community functioning in bipolar disorder, as found in schizophrenia. Given commonalities (i.e. genetic, clinical, and neurobiological) between schizophrenia and bipolar disorder, we hypothesized that neurocognition would predict community functioning in our bipolar sample, and that social cognition would at least partially mediate this relationship.
200 bipolar patients and 49 healthy controls were administered and compared on a battery of tests assessing neurocognition, social cognition, and community functioning. We conducted a series of regression analyses to investigate potential mediation (or exploratory moderation) of social cognition on the relationship between neurocognition and community functioning. Results showed that bipolar patients performed worse on neurocognitive domains of processing speed, attention, verbal learning, and global neurocognition. Also, bipolar patients performed worse on theory of mind, a social cognition composite score, and community functioning. Neurocognition did not significantly predict functional outcome in our bipolar sample. However, we found a moderating effect of social cognition: among patients with poor social cognition, better neurocognition was associated with better community functioning, a relationship not seen in bipolar patients with good social cognition.
While no mediation was observed, an exploratory analysis discovered that social cognition moderated the neurocognition-functioning relationship. Moderation, better known as an interaction, explains when or for whom an independent variable most strongly (or weakly) influences a dependent variable. Specifically, deficits in neurocognition appear to contribute more prominently to community outcome in those with poor social cognition than it does for those with good social cognition. This may suggest that neurocognitive intervention may have a bigger impact upon community functioning in this particular subgroup of patients. Overall, these results suggest that the association between neurocognition and community functioning in bipolar disorder may be dependent on social cognition level, implying the presence of social cognitive heterogeneity, and may be relevant to choosing proper treatment strategies depending on the patient's social cognitive level.