Abstract
Emotion dysfunction has long been considered a cardinal feature across psychotic disorders, including schizophrenia and affective psychosis. However, few studies have used objective markers of emotional function to compare psychotic disorders to one another, and fewer studies have examined such markers within a longitudinal framework. Here, we examine one objective marker of emotional responsivity, the late positive potential (LPP), which is a centro-parietal event-related potential (ERP) that tracks the dynamic allocation of attention to emotional vs. neutral stimuli. We used the LPP to characterize abnormal emotional responsivity by relating it to negative, depressive, and psychotic symptoms among two clinical groups: individuals diagnosed with affective psychosis and individuals with schizophrenia. We also used a long-term longitudinal framework, examining concurrent associations between LPP amplitude and symptom severity, as well as prospective associations with symptoms 4 years later. Participants were 74 individuals with psychotic illness: 37 with schizophrenia spectrum disorders and 37 with a primary affective disorder (psychotic bipolar disorder, psychotic depression). There were no mean-level differences in LPP amplitude between the schizophrenia spectrum and primary affective psychosis group. In the primary affective psychosis group, reduced LPP amplitude was associated with greater depressive, negative, and psychotic symptom severity, both concurrently and at follow-up; associations between LPP and symptoms were not observed within the schizophrenia spectrum group. This pattern of results suggests that the neural correlates of emotion dysfunction may differ across psychotic disorders. One possibility is that schizophrenia is characterized by a decoupling of symptom severity and emotional processing. Such findings underscore the importance of analyzing transdiagnostic samples to determine common or specific symptom relationships across various patient populations.
Highlights
IntroductionEmotion dysfunction is present in various forms across psychotic disorders, manifesting as negative (e.g., flattened affect), and depressive symptoms (e.g., anhedonia), and even potentially contributing to psychotic symptoms (e.g., paranoia)
Emotion dysfunction is present in various forms across psychotic disorders, manifesting as negative, and depressive symptoms, and even potentially contributing to psychotic symptoms
We found modest evidence for negative associations between depressive and psychotic symptom severity and Late Positive Potential (LPP) amplitude
Summary
Emotion dysfunction is present in various forms across psychotic disorders, manifesting as negative (e.g., flattened affect), and depressive symptoms (e.g., anhedonia), and even potentially contributing to psychotic symptoms (e.g., paranoia) It is currently unclear whether abnormal emotional processes differ across psychotic disorders, and whether emotional processes show differential relationships to symptoms, potentially yielding clinically distinct phenotypes. In order to answer such questions, one recent push in clinical science has been the identification of objective neural markers which demonstrate relationships with symptoms [1, 2] Such markers have the potential to objectively index symptom severity, assist in differential diagnosis, and aid in further understanding the mechanisms that underlie emotional disturbances across psychotic disorders [1,2,3]. Some evidence suggests those at-risk for developing depression demonstrate reduced LPP amplitude to pleasant, unpleasant, and neutral stimuli when compared to lower-risk samples [14, 16]. Consistent evidence suggests lower LPP compared to controls in those with primary affective disorders while evidence for lower LPP in schizophrenia spectrum disorders is less consistent
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