Despite the variety of psychotherapeutic models and the differences between the different approaches used in psychotherapy, it turns out that the basis of successful psychotherapy is the strength of the relationship between client and therapist.

A number of scientific studies have concluded that the outcome of psychotherapy depends much more on the therapeutic relationship between the therapist and the client, than on the particular type of psychotherapy.

In 2014, a specially formed Task force at the APA conducted a study, according to which

"The therapeutic relationship makes substantial and consistent contributions to psychotherapy outcome independent of the specific type of treatment. The therapy relationship accounts for why clients improve (or fail to improve) at least as much as the particular treatment method.”

The elements that have been established as proven effective for successful psychotherapy are the therapeutic alliance (relationship) in individual psychiotherapy, empathy and collecting client feedback.

Elements thought to contribute to treatment outcomes are consensus on treatment goals, collaboration, and positive regard, while congruence/genuineness, reparing alliance ruptures, and managing countertransference are promising but insufficiently studied.