Longitudinal Impact of the ACT-Based Positive Psychology Intervention to Improve Happiness, Mental Health, and Well-Being

Abstract This study aims to examine the effectiveness of ACT-based positive psychology intervention on young people's mental health and well-being. Existing literature offers limited insights into the impacts of ACT-based PPIs, particularly concerning young people. The study explores the potential of this intervention to enhance positive psychological outcomes such as subjective well-being, self-compassion, and optimism, while reducing negative psychological outcomes like pessimism, anxiety, depressive symptoms, and somatic symptoms, and improving resilience. Conducted at a state university, the study involved 42 participants between the ages of 19 and 23 who were assigned to experimental ( n = 20) and control ( n = 22) group. The experimental group participated in an 8-week ACT-based PPI program. Employing a longitudinal experimental design, the study included a pre-test, post-test, and a follow-up test approximately two years later. Results indicated that the experimental group experienced significant improvements in positive psychological outcomes and reductions in negative outcomes, with the effects sustained during the follow-up period. Notably, long-term enhancements in resilience and self-compassion were observed. Overall, this study provides important evidence of the effectiveness of ACT-based PPI in promoting young people's long-term outcomes, with implications for developing intervention programs to support their mental health and well-being.