Initially, Sigmund Freud developed a talking cure called psychoanalysis; then he wrote about his therapy and popularized psychoanalysis. After Freud, many different disciplines splintered off. Some of the more common therapies include: psychodynamic psychotherapy, transactional analysis, cognitive behavioral therapy, gestalt therapy, body psychotherapy, family systems therapy, person-centered psychotherapy, and existential therapy. Hundreds of different theories of psychotherapy are practiced (Norcross, 2005, p. 5).A new therapy is born in several stages. After being trained in an existing school of psychotherapy, the therapist begins to practice. Then, after follow up training in other schools, the therapist may combine the different theories as a basis of a new practice. Then, some practitioners write about their new approach and label this approach with a new name.A pragmatic or a theoretical approach can be taken when fusing schools of psychotherapy. Pragmatic practitioners blend a few strands of theory from a few schools as well as various techniques; such practitioners are sometimes called eclectic psychotherapists and are primarily concerned with what works. Alternatively, other therapists consider themselves to be more theoretically grounded as they blend their theories; they are called integrative psychotherapists and are not only concerned with what works, but why it works (Norcross, 2005.For example, an eclectic therapist might experience a change in their client after administering a particular technique and be satisfied with a positive result. In contrast, an integrative therapist is curious about the "why and how" of the change as well. A theoretical emphasis is important: for example, the client may only have been trying to please the therapist and was adapting to the therapist rather than becoming more fully empowered in themselves.
Assimilative integration is the fourth route and acknowledges that most psychotherapists select a theoretical orientation that serves as their foundation but, with experience, incorporate ideas and strategies from other sources into their practice. "This mode of integration favors a firm grounding in any one system of psychotherapy, but with a willingness to incorporate or assimilate, in a considered fashion, perspectives or practices from other schools" (Messer, 1992, p. 151). Some counselors may prefer the security of one foundational theory as they begin the process of integrative exploration. Formal models of assimilative integration have been described based on a psychodynamic foundation (Frank, 1999; Stricker & Gold, 2005) and based on cognitive behavioral therapy (Castonguay, Newman, Borkovec, Holtforth, & Maramba, 2005).
Govrin (2015) pointed out a form of integration, which he called "integration by conversion", whereby theorists import into their own system of psychotherapy a foreign and quite alien concept, but they give the concept a new meaning that allows them to claim that the newly imported concept was really an integral part of their original system of psychotherapy, even if the imported concept significantly changes the original system. Govrin gave as two examples Heinz Kohut's novel emphasis on empathy in psychoanalysis in the 1970s and the novel emphasis on mindfulness and acceptance in "third-wave" cognitive behavioral therapy in the 1990s to 2000s.
An approach called integral psychotherapy (Forman, 2010; Ingersoll & Zeitler, 2010) is grounded in the work of theoretical psychologist and philosopher Ken Wilber (2000), who integrates insights from contemplative and meditative traditions. Integral theory is a meta-theory that recognizes that reality can be organized from four major perspectives: subjective, intersubjective, objective, and interobjective. Various psychotherapies typically ground themselves in one these four foundational perspectives, often minimizing the others. Integral psychotherapy includes all four. For example, psychotherapeutic integration using this model would include subjective approaches (cognitive, existential), intersubjective approaches (interpersonal, object relations, multicultural), objective approaches (behavioral, pharmacological), and interobjective approaches (systems science). By understanding that each of these four basic perspectives all simultaneously co-occur, each can be seen as essential to a comprehensive view of the life of the client. Integral theory also includes a stage model that suggests that various psychotherapies seek to address issues arising from different stages of psychological development.