Shapiro D A
Br J Med Psychol. 1976 Dec;49(4):315-23. doi: 10.1111/j.2044-8341.1976.tb02383.x.
This paper surveys evidence relating the 'therapeutic conditions' of Accurate Empathy, Non-Possessive Warmth and Genuineness to psychotherapeutic outcome. The studies reviewed include comparisons of 'good' therapy with no-treatment control groups, and correlational studies relating levels of 'conditions' to outcome. Even leaving aside the question of the validity of the outcome measures used, it is concluded that present evidence suggests no more than a weak relationship between these 'conditions' and patient improvement. It is suggested that a methodologically adequate, experimental, demonstration of their effectiveness has yet to be attempted.