While we assume that the skills we teach to clients are an important part of the effectiveness of CT, relatively few studies have tested to see if this is indeed the case. In a recent study Strunk, et al. (2007) examined whether clients' competence in using CT skills and their independent use of the skills is related to the risk of relapse. They studies 35 moderately- to severely-depressed individuals who responded to CT. Both competence in CT skills and in-session evidence of independent use of CT skills predicted lower relapse rate. This effect was not accounted for by symptom severity, degree of symptom change over the course of treatment, or post-treatment self-esteem.

Strunk, D. R., DeRubeis, R. J., Chiu, A. W., & Alvarez, J. (2007). Patients' competence in and performance of cognitive therapy skills: Relation to the reduction of relapse risk following treatment for depression. Journal of Consulting and Clinical Psychology, 75, 523-530.