Interaction effects of Irritability and Anhedonia on ERP and Time-Frequency Measures of Reward Sensitivity

Irritability and anhedonia are two prevalent, co-occurring, and impairing symptoms of major depression that are proposed to result from dysfunctions in reward processing. While irritability is associated with heightened sensitivity to reward receipt, anhedonia is linked to blunted sensitivity to reward receipt. Given these supposed paradoxical effects on reward sensitivity, it is noteworthy that no studies have examined how both symptoms interact to affect reward sensitivity. In a community sample of young adults (N=73, Mage=21.21±2.27, 56.16% females), we evaluated the interacting effects of dimensionally-assessed irritability and anhedonia symptoms on neural (i.e., event-related potentials and time-frequency) measures of reward and loss sensitivity during the Doors task, a well-known reward paradigm. We used univariate and multivariate (based on generalized eigendecomposition) approaches to isolate patterns of delta and theta activity in response to reward and loss. General linear models tested the unique and interacting effects of irritability and anhedonia on EEG measures of reward sensitivity (Feedback-Related Negativity [FRN], Reward Positivity [RewP], theta, and delta power). Results revealed a significant interaction effect of irritability and anhedonia on the FRN to loss (R2=.13, F(3, 69)=3.35, β=-.03, p<.01). Specifically, anhedonia was associated with larger (i.e., more negative) FRN to loss only in the presence of high irritability. At low levels of irritability, anhedonia was associated with smaller (i.e., more positive) FRN to loss. We also found that anhedonia was associated with reduced theta power to win (R2=.20, F(3, 69)= 5.89, β=-.01, p<.01) at mean and high irritability levels. These effects remained significant when controlling for broader depressive symptoms, gender, and income. These findings provide preliminary evidence of an interactive effect of anhedonia and irritability on neural sensitivity to both reward and loss in individuals without clinical levels of symptoms. Our results highlight the importance of considering symptom interactions to better understand reward-related mechanisms in depression.