Transpersonal psychology is a sub-field or "school" of psychology that integrates the spiritual and transcendent aspects of the human experience with the framework of modern psychology. It is also possible to define it as a "spiritual psychology". The transpersonal is defined as "experiences in which the sense of identity or self extends beyond (trans) the individual or personal to encompass wider aspects of humankind, life, psyche or cosmos". It has also been defined as "development beyond conventional, personal or individual levels".
Issues considered in transpersonal psychology include spiritual self-development, self beyond the ego, peak experiences, mystical experiences, systemic trance, spiritual crises, spiritual evolution, religious conversion, altered states of consciousness, spiritual practices, and other sublime and/or unusually expanded experiences of living. The discipline attempts to describe and integrate spiritual experience within modern psychological theory and to formulate new theory to encompass such experience.
Transpersonal psychology has made several contributions to the academic field, and the studies of human development, consciousness and spirituality. Transpersonal psychology has also made contributions to the fields of psychotherapy and psychiatry.
Lajoie and Shapiro reviewed forty definitions of transpersonal psychology that had appeared in academic literature over the period from 1968 to 1991. They found that five key themes in particular featured prominently in these definitions: states of consciousness; higher or ultimate potential; beyond the ego or personal self; transcendence; and the spiritual. Based upon this study the authors proposed the following definition of transpersonal psychology: Transpersonal Psychology is concerned with the study of humanity's highest potential, and with the recognition, understanding, and realization of unitive, spiritual, and transcendent states of consciousness.
In a review of previous definitions Walsh and Vaughan suggested that transpersonal psychology is an area of psychology that focuses on the study of transpersonal experiences and related phenomena. These phenomena include the causes, effects and correlates of transpersonal experiences and development, as well as the disciplines and practices inspired by them. They have also criticised many definitions of transpersonal psychology for carrying implicit assumptions, or presuppositions, that may not necessarily define the field as a whole.