How the psychotherapy research community must work toward measurement validity and why.

The clinical and the scientific value of the whole psychotherapy research enterprise depends upon the construct validity of its Mental Health Status (MHS) measurements. This is essentially a matter of conceptual validity, that is, what we agree that MHS reasonably means. Any theory of psychotherapy can be true only insofar as it involves independent variables that have demonstrated causal relevance to such conceptually valid measurements of MHS, which is also what makes the measurements of these independent variables predictively valid. Every published efficacy, effectiveness, and case study that tests or explores for explanations of MHS ought to involve the same conceptually valid MHS measures, but the necessary validity is still undemonstrated. It cannot be demonstrated unless the research community reaches a conceptual consensus on MHS, a consensus that decisive psychotherapy research must await. 2004 Wiley Periodicals, Inc.