LAUSR

Abstract Objective Social interactions are vital for our well‐being, particularly during times of stress. However, previous studies linking social interactions to psychological outcomes during the COVID‐19 pandemic have largely been retrospective and/or cross‐sectional. Thus, we tested four preregistered hypotheses (H1–H4) concerning the real‐time effect of social interactions on momentary changes in stress and mood during two COVID‐19 lockdowns. Design We used an ecological momentary assessment approach in 732 participants in spring 2020 (burst 1) and in a subsample of these participants (n = 281) during a further lockdown in autumn/winter 2020 (burst 2). Methods Participants reported their stress and mood in a smartphone app five times per day for 7 days and indicated the nature and frequency of their recent social interactions. Results Social interactions (H1) and their frequency (H2) improved momentary affect (e.g., social interactions increased mood valence: estimate = 2.605, p < .001 for burst 1). This was particularly the case for face‐to‐face interactions which, compared with other types of interactions, reduced momentary stress (e.g., estimate = −2.285, p < .001 for burst 1) and boosted mood (e.g., estimate = 1.759, p < .001 for burst 1) across both lockdowns, even when controlling for the pleasantness of the interaction and the closeness of the interaction partner (H3). We also show that individual differences in people's responsiveness to different social rewards modulated the impact of social interactions on momentary mood (H4). Conclusions This study extends findings from cross‐sectional and retrospective studies by highlighting the real‐time affective benefits of social interactions during COVID‐19 lockdown. The results have important implications for the (self‐) management of stress and mood during psychologically demanding periods.