What factors in the patient make him susceptible to the influence of the psychotherapist (influencer, healer, physician, etc), and what factors at the disposal of the psychotherapist enable him to exert an effect on the patient's suggestibility, persuasibility, or amenability to social influence? A person's susceptibility to psychological influence is rooted in early experiences which are crucial in determining his responsiveness to psychotherapy in later life. Defense mechanisms regulate this susceptibility. A significant amount of psychotherapeutic change is attributable to so-called nonspecific factors which operate on loci of influenceability. Concomitantly, the therapist in all forms of psychotherapy judiciously deploys interpersonal power in the direction of undermining defenses against basic trust. Thus, he intervenes in a field of forces producing rearrangements which are usually referred to as "therapeutic changes."
Strupp HH. On the Technology of Psychotherapy. Arch Gen Psychiatry. 1972;26(3):270-278. doi:10.1001/archpsyc.1972.01750210078015