Trained in Schema Therapy and Gestalt Therapy, he created the Transformational Chairwork approach and is currently teaching this method of psychotherapeutic dialogue to practitioners in both the United States and abroad. ! In his writings, he has looked at such topics as addiction treatment, identity theory, trauma and violence, contingency management, harm reduction, and assessment. Dr. Kellogg has also written on Schema Therapy, borderline personality disorder, and the integration of Gestalt techniques in cognitive-behavioral treatment.