In this article, we provide an overview of Bowlby's theory of attachment, its revisions, and related constructs, and describe how attachment may underlie many of the processes of psychotherapy. Modern psychotherapy research, plagued by the omnipresent "dodo bird" that has consistently determined that most psychotherapy modalities appear to have similar levels of effectiveness, has moved toward attempting to understanding mechanisms of change underlying treatment outcomes. Delineating the ways in which attachment theory may form the foundation for psychotherapy processes may help answer the call for change mechanisms and common therapeutic factors. In this article, we outline attachment theory as it applies to both children and adults, focusing specifically on its relevance for psychotherapy, followed by a review of the current empirical findings regarding the connection between attachment and psychotherapy. Finally, we highlight a series of existing psychotherapeutic modalities and techniques that are relevant for understanding the relationship between these domains and extend these examples to other forms of psychotherapy and psychotherapy process more broadly. Attachment provides a comprehensive yet parsimonious foundation for psychotherapy research and practice, with implications for enhancing treatments, personalizing care, and explaining the process of psychotherapeutic change.
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