Optimism bias is both a cross-sectional and a longitudinal predictor of positive mood

Healthy people tend to rate positive events as being more likely to happen to them than negative events. Here, we call this ‘optimism bias’. Other operationalisations of optimism are associated with mood, affect, and mental well-being; however, we do not yet have a clear picture of the relationship between optimism bias and mood. We examined these relationships by re-analysing three of our existing datasets, collected from students in Istanbul. In Study 1, optimism bias showed a substantial cross-sectional correlation with positive mood, but not with negative mood; its correlation with positive mood was distinct from its correlation with depressive symptom severity. In Studies 2 and 3, optimism bias longitudinally predicted positive mood, 1 and 4 weeks later. This longitudinal relationship was specific: optimism bias did not predict later negative mood, or depressive or anxious symptoms; none of these other variables reliably predicted later positive mood. Furthermore, the longitudinal relationship was unidirectional, in that positive mood did not predict later optimism bias. Future research should investigate whether this longitudinal relationship operates within- or between-persons, and whether optimism bias might be a potential target for mood interventions.