The relationship between case conceptualization and homework in cognitive behavioural therapy (CBT) for depression : a thesis in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Psychology at Massey University, Albany, New Zealand
Comprehensive case conceptualization is central to Cognitive Behavioural Therapy
(CBT; A. T. Beck, Rush, Shaw, & Emery, 1979). Despite the importance attributed to case
conceptualization there is limited empirical support for the utility of case conceptualization in
CBT. In particular, there is limited research on the relationship between therapist competence
in case conceptualization, in-session and between session treatment planning (i.e.,
homework), and outcomes. Furthermore, little is known about the evolution of case
conceptualization over a course of CBT. In order to facilitate the empirical investigation of
case conceptualization in CBT the primary aim of the current thesis was to develop a new
method for evaluating case conceptualization, the Conceptualization Rating Scale (CRS;
Easden & Kazantzis, 2008; 2009).
Study 1 investigated how patients’ (n =10) written case conceptualizations change
over a course of CBT for depression using 53 J. Beck Case Conceptualization Diagrams (J.
Beck, 1995). Therapist’s resultant case conceptualizations became more complete over the
course of therapy with an average of 33% more information being recorded in case
conceptualizations from intake to session 10. Consistent with cognitive-behavioural theory,
therapists tended to conceptualize core beliefs about the ‘self’ with relatively minimal
reporting of beliefs about the ‘world / others’ and the ‘future’.
Study 2 provided the training, development and preliminary psychometrics of the
CRS. Independent observers (N = 4) rated 225 DVD recorded therapy sessions. The CRS was
demonstrated to possess adequate internal consistency (α = .61) and excellent total scale
interrater reliability for each of the four domains integration (k = .83), importance (k = .65),
competence (ICC = .93), and fit / match (ICC = .86). Results revealed that independent observers were able to agree on different aspects of CBT therapist’s utilization of case
conceptualizations during therapy sessions.
In Study 3, using the total sample of 28 patients, therapist’s (N = 7) levels of
competence were assessed by independent observers (N = 4) using the CRS based on 225
DVD recorded therapy sessions. A multilevel modelling (MLM) analysis revealed that after
controlling for time, taken together, therapist competence in homework use and therapist
competence in case conceptualization explained 40% of within patient variance and 19% of
between patient variance associated with positive change on the BDI-II after controlling for
patient beliefs about homework, symptom severity and personality beliefs.
The results from each study contribute towards an understanding of the relationship
between different domains of therapist competence and outcomes in psychotherapy. More
specifically, empirical support is provided for the utility and systematic integration of case
conceptualization in CBT for depression. Implications are discussed for supervision, training
and clinical practice in CBT to ensure positive patient outcomes and evidenced-based
interventions in CBT.