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 measures of reward and loss sensitivity during a well-established reward paradigm (the Doors task). Event-related potential and time-frequency measures were analyzed using both univariate and a multivariate method based on generalized eigendecomposition to isolate delta- and theta-band activity in response to feedback. Linear-mixed models tested the unique and interacting effects of irritability and anhedonia on EEG measures of reward sensitivity (FRN/N2, theta, and delta power). Participants with above-average irritability and anhedonia displayed larger (more negative) FRN/N2 amplitudes across feedback valence, and reduced theta power following reward feedback, whereas no associations were observed at lower symptom levels. These findings suggest that individuals with co-occurring irritability and anhedonia may perceive feedback overall (reward and loss) as more salient, while interpreting rewards as less motivationally relevant. These effects remained significant when controlling for broader depressive symptoms, gender, and income. These results provide preliminary evidence that co-occurring irritability and anhedonia jointly influence neural sensitivity to feedback, in individuals without clinical levels of symptoms. Awaiting validation in clinical samples, our results highlight the importance of considering symptom interactions to better understand reward-related mechanisms in depression.