The integration of psychotherapies can take several forms. They are complementary and have common elements. They have a slightly different focus and starting point. Each has its own strengths, challenges and pitfalls.

 

1. Theoretical integration aims to create a meta-model of therapy. It aims to create a theory of theories, using all the theoretical information available in all therapeutic approaches and trying to reconcile the so-called contradictions between them. These meta-models mostly focus on what is common to different psychotherapeutic theories and use this as a basis for integration. 
   Although processing all the information present in the different therapeutic orientations is a huge task and no meta-model has yet managed to do an exhaustive job, these initiatives are of great help to practicing psychologists/psychotherapists. 
   It may be utopian to expect a single meta-model that encompasses all the information related to psychotherapy. Yet, these initiatives, if they do not claim to be exclusive, can make a significant contribution to the integration of psychotherapies.

2. Technical eclecticism approaches integration from the practical side.
   Guided by "what can help here and now for this client's particular problem".
   It does not seek to create a theoretical model that can be used to interpret the therapeutic process and determine the technique to be used, but rather seeks to find the most effective method for the problem at hand, based on experience. 
   The danger is that it slips towards the extreme of: it doesn't matter that we don't understand how it works, it just hat it works. 
   This kind of pragmatism risks applying to a client techniques that come from different psychotherapeutic orientations, that explain the psychotherapeutic process with a set of concepts that at first sight seem contradictory, and that, if not clarified, may confuse the client. Failure to resolve this confusion may reduce the effectiveness of the therapeutic methods and hinder the therapeutic process. Furthermore, to be able to identify, without any theoretical reflection on the part of the therapist, which method is the most appropriate to use with a given client for a given problem requires a great deal of practice and a highly developed intuitive sense, which is not at all expected of professionals, especially those at the beginning of their careers.
   It is necessary that technical eclecticism is increasingly complemented by a theoretical reflection.

3. The common factors approach is based on the assumption that different psychotherapeutic approaches, with their specific conceptual framework, actually describe the same reality of recovery in therapy, and that their methods mobilise the same general factors. The proponents of this approach advocate the development of a common psychotherapeutic language based on common factors, which would make it easier for therapists trained in different approaches to understand each other. Such a common language would also make it possible to promote psychotherapeutic knowledge more clearly and comprehensibly to the general public.
   If such a language were to be developed, it is important to ensure that the specific terminology of each therapeutic modality is not forgotten, as diversity enriches. Describing the same reality in a variety of concepts and images can help each client to find the most convenient way to receive the information necessary for his or her recovery.

4. In integrative assimilation, a therapist trained in a particular therapeutic modality uses techniques from other therapeutic modalities, integrating them into his or her own therapeutic practice. In this case, the therapist remains within the conceptual framework of his or her own therapeutic orientation. This integration is necessary when the therapist encounters a gap in his or her own conceptual framework. The therapist adopts theoretical elements from the therapeutic modality whose techniques he is using, but incorporates them into his own modality in such a way that it retains its identity.
   This requires in-depth knowledge of the conceptual framework of the therapist's own therapeutic modality, otherwise the therapist risks either stepping outside the framework of his or her own therapeutic modality or creating a contradiction between his or her own original theoretical system and the theoretical elements adopted. In the first case, he can no longer call himself a representative of the school of thought in which he was trained, he will no longer remain loyal to his own school of thought, and in the second case, the contradiction will reduce the effectiveness of the therapeutic process.

5. Complementarity is the way in which two or more therapeutic approaches are combined to create a new approach. This new trend carries the strengths of the trends from which it is derived, so that it can be more effective than those trends. In this way, cognitive-behavioural therapy has emerged from a combination of cognitive and behavioural therapies, and dialectical behavioural therapy from a combination of cognitive-behavioural therapies and Zen principles. Here too, it is important to have a thorough knowledge of the initial orientations, so that their integration can result in a coherent new system capable of providing a framework for the therapeutic process.

6. The results of neuropsychological research can provide a basis for integration efforts. These studies have shown that the relationship between infant and mother contributes to the development of neural pathways in the infant's brain that are responsible for emotion regulation and metacognitive processes. 
   Regardless of the therapeutic approach, the therapeutic relationship involves similar neurological processes to those between the infant and its mother. The study of these processes at the level of the nervous system can provide a basis for the formulation of integrative psychotherapeutic models.
   Research at the level of the nervous system is still far from being able to provide a unified model of the neurological underpinnings of psychological processes. There are different models that have yet to be scientifically validated. However, information is already available that offers hope for integration efforts.