Abstract. Acceptance and commitment therapy (ACT) is recognized as a transdiagnostic and one of the effective therapeutic intervention approaches for depression in young adults and university students with a proven extended significant benefit. ACT’s core goals are to be psychologically flexible and less prone to depression. However, although numerous studies demonstrated ACT’s effectiveness, it is necessary to address the gap in determining whether the efficacy is consistent with previous research that mostly applied randomized controlled trials (RCTs). This study utilized a rare approach in navigating its efficiency among an underrepresented sample of Filipino students in a local university. This research applied a longitudinal-naturalistic single-group design within a two-month interval between baseline and post-intervention data among 124 participants. Relevant data were gathered using the Quick Inventory for Depressive Symptomatology – Self-Rated Version (QIDS-SR) in evaluating depressive levels and symptomatology and the Multidimensional Psychological Flexibility Inventory (MPFI) for identifying psychological flexibility and inflexibility. The results demonstrated significant changes with a p-value of 0.000 and an effect size d of .85. More so, it can be surmised that the value of F (2, 121) = 33.80 with a p-value less than 0.05 significantly impacted depression. Hence, ACT psychoeducation group intervention through a synchronous online platform alleviated the depression symptoms among students in a local university. Also, data proved that psychological flexibility and inflexibility have a significant impact on depression. Thus, the potential utilization and inclusion of psychoeducation based on ACT in the course and counseling program among college students is highly suggested.

Keywords: Acceptance and commitment therapy; Depression; Psychological flexibility and inflexibility; Longitudinal-naturalistic study; Filipino.