Single bout of exercise reduces self-reported and decoded rumination in favor of distraction in patients with major depression

One key feature of depressive disorders is rumination, which is associated with the onset, duration, and severity of the disorder. Moderate-intensity physical exercise (ME) has been established as treatment for depression. The "Distraction-Hypothesis" assumes that exercise ameliorates depression because it distracts individuals from ruminative thoughts. We investigated whether a single bout of ME reduces self-reported rumination, shifts individuals' mental state from rumination to distraction, and the temporal dynamics of these effects. Participants conducted single bouts of ME (105 % of the lactate threshold) compared to a sedentary control condition (SED), both lasting 30 min. The sample consisted of n = 24 moderately or severely depressed participants. To assess the temporal dynamics of rumination, the study continuously measured self-reported rumination via visual analogue scales (VAS) and decoded rumination versus distraction from individual EEG patterns as primary outcomes. The ME condition reduced self-reported VAS-rumination more strongly than the SED condition (F(6, 343.05) = 4.44, p < .001, η_p = 0.07), with significant differences between groups at minutes 10, 15, 20, 25 and 30 of the intervention. Over the whole time course of the exercise intervention, ME reduced the probability of decoded rumination in favor of decoded distraction (F(1, 117) = 9.46 p = .003, η_p = 0.07) in a subsample of n = 10 individuals, for whom prior decoding from EEG was successful. This study supports the Distraction-Hypothesis by showing that ME reduces self-reported and decoded rumination and increases the likelihood of distraction from rumination. OSF-registration: 10.17605/OSF.IO/APCX9.