Depressive symptoms moderate diurnal variation in response-inhibition-related neural activity among patients with...

Impaired response inhibition represents a core cognitive deficit in depression, yet its potential diurnal fluctuations remain unexplored. While healthy populations exhibit synchrony effects (chronotype dependent time-of-day variations) in inhibitory control, whether such circadian modulation persists in depressive disorders is unknown.

73 patients with depressive episode (DEs) and 70 healthy controls (HCs) performed a visual Go/NoGo task during morning (08:30-10:00) and evening (18:30-20:00) electroencephalography (EEG) sessions. EEG data were analyzed using event-related potentials and event-related spectral perturbation. The Generalized Estimating Equation was used to test the Group × Time interaction and moderation effect between Time and chronotype, sleep quality, as well as severity of depressive symptoms. Bayesian factors (BF) were calculated to quantify evidence for null effects.

After controlling age, sex, education and medication, there was a significant Group × Time interaction effect (Wald χ²(1) = 5.346, p = 0.021). Post-hoc tests indicated that P3 amplitude was significantly lower in the DEs during the morning session compared to during the evening session (p = 0.042, Bonferroni correction). No significant effects were observed for Alpha and Beta oscillations (all p > 0.05, BF < 0.394). The diurnal variation of P3 amplitude was moderated by severity of depressive symptom (Wald χ²(1) = 5.945, p = 0.015), but not chronotype and sleep quality.

Depressive patients show a specific diurnal pattern of response-inhibition-related neural activity, moderated by severity of depressive symptoms. Future research assessing inhibitory control in depression must systematically account for the time of measurement.