Harnessing the Transdiagnostic Power of ACT: A Case Study in Treating Prolonged Grief and Co-Occurring Symptoms

Prolonged Grief Disorder (PGD) is characterized by persistent, intense emotional distress following a loss and often results in significant functional impairment. While cognitive behavioral therapies (CBT), including third wave approaches such as Acceptance and Commitment Therapy (ACT), have demonstrated effectiveness in treating PGD, many individuals with PGD also experience co-occurring symptoms like depression, anxiety, and trauma. In such cases, traditional treatment models that target one set of symptoms may be insufficient. This case study examines the application of ACT with a 65-year-old Latina woman presenting with symptoms consistent with PGD, as well as co-occurring depression, anxiety, and trauma symptoms following the death of her son. ACT’s transdiagnostic, process-based approach was used to foster psychological flexibility and reduce experiential avoidance, supporting the client in living a meaningful life alongside her pain. Rather than assigning a DSM-5-TR diagnosis, the therapist and supervisors chose to use an ICD-11 Z-code to avoid pathologizing the client’s grief. Over the course of treatment, the client demonstrated significant cross-cutting symptom improvement. This case highlights the clinical utility of ACT for complex grief presentations and the value of intentional diagnostic decision-making within evidence-based interventions.