The study analyzes the treatment by copsychotherapy of 56 individual patients carried out by a male-female therapist pair. The therapeutic contributions of the female cotherapist are scored (from evidence in the process notes) in terms of thirteen factors, and are listed in order of importance. Her contributions are greatest in the treatment of borderline psychotic personality disorders.

Publications regarding the joint psychotherapy of individual patients or couples describe a variety of therapist-pairings, many styles of treatment approach, and an increasing interest, in the last two decades, in a treatment tool which impresses workers as having particular therapeutic effect with both research and training potential. The pairings of therapists show many permutations by profession, previous experience, and relatedness. In this ongoing study the partners are a male psychoanalytically trained psychiatrist and a female social psychology graduate. The style used has been referred to as multiple therapy although the term co-psychotherapy is less ambiguous and more specific. Patients seen in private practice readily accepted the joint participation of the junior partner, no matter whether they were already underway in psychotherapy or were newly referred. Co-psychotherapy appears to be more effective than single-handed psychotherapy, especially in the treatment of psychotic and borderline patients. When one member of a therapeutic pair is a trainee, co-psychotherapy offers an apprenticeship in psychotherapy by direct and intense immersion. Its value as part of psychotherapy training would seem to warrant more extensive deployment.