title: Constrained, confounded and confused: why we really know so little about therapists in treatment outcome research.
authors.forename: K M
authors.initials: KM
authors.lastname: Carroll
mesh_terms: D001521:Behavior Therapy / Q000193:education* / Q000592:standards; D002983:Clinical Competence; D006801:Humans; D019966:Substance-Related Disorders / Q000628:therapy*; D016896:Treatment Outcome