Sudden Gains and Losses in Personality Change Interventions: Predictors, Outcomes, and Implications for Individualized Personality Change

Recent research suggests that volitional personality change is possible through structured interventions, yet little is known about its temporal dynamics. In psychotherapy research, sudden gains—abrupt, substantial improvements between sessions—robustly predict treatment outcomes. Based on 448 Swiss participants who completed a 12-week personality intervention, we examined whether similar sudden shifts occur during volitional personality change and whether they explain differences in trait, life satisfaction, and self-esteem changes. We compared four measures for detecting shifts, of which weekly measures of personality states performed best. Sudden gains in weekly states occurred in only 7.6% of participants—roughly twice the rate expected from measurement fluctuation alone, but far below rates found in psychotherapy. For this small subgroup, however, intervention effects were 2.7 to 3.4 times stronger than for participants without sudden gains. Sudden gains were more likely to occur in weeks in which participants were more motivated to change, and were followed by increased general change factors (i.e., insight, behavioral practice, and strengths activation). Sudden losses in weekly states were less frequent and showed no meaningful negative effects. These findings underscore the value of capturing dynamic, within-person fluctuations. Monitoring and leveraging such shifts may help personalize interventions and optimize their impact.