Motivational negative symptoms of schizophrenia (SZ) are predictors of poor functional outcome and are notoriously difficult to treat. These symptoms also occur in bipolar disorder with psychotic features (BPP), although it is unclear how they are developed and maintained both within and across diagnoses (SZ or BPP). Pupillometry can be used as a tool to clarify said mechanisms. Blunted dilation as a function of cognitive demands has been interpreted as a metric of diminished effort while blunted constriction to light has been interpreted as a metric of blunted autonomic balance and both have been found to be reduced in individuals with schizophrenia and related to increased motivational negative symptom severity. However, associations between these two sets of findings in the same individuals have not yet been investigated. Blunted cognitive-related dilation has also been observed in individuals with BPP compared to healthy controls, but relationships with motivational negative symptoms have not been examined. To investigate these two lines of research, I first computed correlations between blunted constriction and blunted dilation in individuals with schizophrenia (n = 55) and then used multi-level modeling (MLM) to determine whether motivational negative symptoms in BPP (n = 30) and SZ (n = 55) are significant predictors of blunted dilation. Results indicate a significant positive correlation between both pupil metrics not explained by motivational negative symptoms. Blunted dilation was replicated in SZ relative to HC but was not found in BPP relative to HC nor SZ. Motivational negative symptoms did not predict blunted dilation. These findings provide, for the first time, evidence for a shared mechanism linking blunted pupil response to light and cognitive demands in SZ. Individuals with schizophrenia may show reduced attentional resource allocation to internal versus external goals. No conclusion can be made as to pupil/symptom relationships in SZ nor transdiagnostically in BPP.
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