Psychological integration: Transtheoretical versus Merging/blending Theories The underlying principle behind psychotherapy integration is that unitary theoretical models are often inadequate in addressing patients’ unique needs. However, it is essential to acknowledge that integrating different theories is a complicated process as several factors (i.e., complications, contradictions, reverberations, and implications) need to be considered (Beutler et al., 2016). These dynamics and other client’s factors would, at times, cause a therapist to go beyond established theoretical faiths. Usually, psychotherapists apply integrative approaches based on experience, skills, and knowledge. They are traditionally prescriptive in merging available theories whereby the “best fit” approaches are used. Furthermore, general literature and studies indicate notable efficacy in integrative approaches (both in merging and blending theoretical models). When it