Reward processing and eveningness in adolescents: A case-control study with EEG investigation

Fiona Yujing Jin, Xibo Zuo, Forrest Tin Wai Cheung, Owen Ho Hin Chu, Yue Pan, You Li, Dandan Liao, Hao Fong Sit, Joey Wing Yan Chan, Ngan Yin Chan, Jihui Zhang, Caroline Ka-sin Shea, Yun Kwok Wing, Xiaoqing Hu, Shriely Xin Li

Abstract

Introduction: Adolescence is often associated with increased evening tendency and the risk of developing mental health problems. Previous research has suggested a close interplay between evening chronotype, which is characterized by an inclination for later bedtime and wake time, and depression, but there has been limited research to investigate the potential mechanism underlying their association. Given that altered reward processing is a key feature of depression, this case-control study examined whether adolescents with an evening preference also exhibit deficits in reward processing.

Materials and methods: Thirty adolescents aged 12–20 (63.33% female) with an evening chronotype (Morningness-Eveningness Questionnaire (MEQ) ≤41) and 30 non-eveningness healthy controls (MEQ ≥42) with matched age and sex were recruited. Participants with a current clinical diagnosis of sleep or psychiatric disorders (except for delayed sleep phase disorder in the eveningness group) or a medical condition that could significantly affect sleep quality were excluded. All participants underwent a clinical interview, followed by completing a battery of self-report questionnaires including Insomnia Severity Index (ISI) for insomnia severity, Beck Depression Inventory-II (BDI-II) for self-reported depressive symptoms, and the subscale of reward responsiveness in Behavioral Inhibition System/Behavioral Activation System (BIS/BAS) scales for the measure of reward responsiveness. The Children’s Depression Rating Scale-Revised (CDRS) was used for measuring clinician-rated depressive symptoms. Participants wore an actigraphy for eight consecutive days and completed a Door Guessing Task as a measure of reward sensitivity using an electroencephalogram.

Results: The eveningness group had higher self-reported and clinician-rated depressive symptoms (both Ps < 0.05) but comparable insomnia severity. In terms of sleep measures, the eveningness group showed significantly longer sleep onset latency, later bedtime, rise time, and sleep midpoint as measured by sleep diary. Actigraphy results showed significantly later sleep onset, sleep offset, and sleep midpoint, as well as shorter total sleep time in the eveningness group compared to healthy controls (all Ps < 0.05). Compared to healthy controls, the eveningness group showed significantly lower signal on reward positivity (RewP) overall without significant difference between conditions (F (1, 51) = 4.35, P = .042), indicating blunted reward processing. On the behavioral level, the eveningness group also showed stronger alterations (switched choices more often) in the trial-by-trial behavioral adjustment analyses (t (7105.0) = 2.57, p = .010). However, there was no significant interaction between group, cue, and choice adjustments. Healthy participants showed significantly different reaction times (gain > neutral, t (7065.2) = –2.21, P = .027), this effect was not found in eveningness participants. Reward responsiveness, as measured by BIS/BAS, was not significantly different between groups.

Conclusions: RewP may reflect the neural deficits in reward processing and has been suggested as a potential early biomarker for depression. The findings on blunted response to reward in adolescents with evening preference may be indicative of the risk for depression in eveningness. Longitudinal studies are necessary to establish causality and explore potential interventions targeting circadian factors in the prevention of youth depression.

Acknowledgments: This work was supported by Health and Medical Research Grants from Food and Health Bureau, Hong Kong SAR (Ref. 21222951, awarded to SXL).

Recommended citation: Jin, F. Y., Zuo, X., Cheung, F. T. W., Chu, O. H. H., Pan, Y., Li, Y., Liao, D., Sit, H. F., Chan, J. W. Y., Chan, N. Y., Zhang, J., Shea, C. K.-s., Wing, Y. K., Hu, X., & Li, S. X. (2026). Reward processing and eveningness in adolescents: A case-control study with EEG investigation. Sleep Medicine, 138, 107149. https://doi.org/10.1016/j.sleep.2025.107149