Tallies were made of outcomes of all reasonably controlled comparisons of psychotherapies with each other and with other treatments. For comparisons of psychotherapy with each other, most studies found insignificant differences in proportions of patients who improved (though most patients benefited). This "tie score effect" did not apply to psychotherapies vs psychopharmacotherapies compared singly—psychopharmacotherapies did better. Combined treatments often did better than single treatments. Among the comparisons, only two specially beneficial matches between type of patient and type of treatment were found.
Our explanations for the usual tie score effect emphasize the common components among psychotherapies, especially the helping relationship with a therapist. However, we believe the research does not justify the conclusion that we should randomly assign patients to treatments—research results are usually based on amount of improvement; "amount" may not disclose differences in quality of improvement from each treatment.
Luborsky L, Singer B, Luborsky L. Comparative Studies of PsychotherapiesIs It True That "Everyone Has Won and All Must Have Prizes"?. Arch Gen Psychiatry. 1975;32(8):995-1008. doi:10.1001/archpsyc.1975.01760260059004