Gratitude, flourishing and prosocial behaviors following experimental sleep restriction and sleep extension

People who are grateful, resilient and flourishing in life show better health, including better sleep. This correlational finding is typically attributed to personality factors or to positive outlooks causing better sleep. We investigated the reverse causal interpretation: do sleep losses and sleep gains experimentally affect feelings and expressions of gratitude, resilience and flourishing? Young adults (N = 90) were randomly assigned to sleep restriction, sleep extension or to sleep normally while wearing wristband actigraphy between Monday and Friday study sessions. State-level measures of flourishing, resilience and gratitude improved across the week with sleep extension and worsened with sleep restriction (ηp2 = .13 to .17). Trait-level measures showed modest or no changes. Sleep-extended participants wrote twice as many details on their gratitude list as the other two conditions (ηp2 = .11). Most effects persisted when accounting for mood. Therefore, subtle changes in nighttime sleep causally influence the components that underlie mental well-being.