Owen, J., Adelson, J., Budge, S., Wampold, B., Kopta, M., Minami, T., & Miller, S. (2015). Trajectories of change in psychotherapy. Journal of Clinical Psychology, 71(9), 817–827.
Knowing the rate, or the trajectory, or the shape of client change across sessions of therapy can inform our understanding of how patients change, our policies of how many sessions to provide clients, and our clinical decisions if clients are no longer improving. The most popular models of client change across sessions include the “dose-effect model” and the “good-enough level model”. The dose-effect suggests that the more therapy patients receive the more they improve but, at a certain point, more sessions result in diminishing returns. In the August, 2013 PPRNet blog, I reviewed a chapter suggesting that 17% to 50% partially improve after about 7 sessions, and 50% patients fully recover after receiving about 21 sessions of therapy. Dose effect models might encourage some agencies to provide only the average number of sessions so that most patients will improve. The good-enough level model, on the other hand suggests that patients stay in therapy for varying lengths of time, and the number of sessions is determined by the point at which they feel better. In this study by Owen and colleagues, the authors take a different approach by looking at the patterns or trajectories of change that represent how and at what rate patients improve over time. In this very large study, they gathered session-by-session outcome data for over 10,000 clients seen at 47 treatment centres by over 500 different therapists. Client presenting problems and therapy orientations varied. Owen and colleagues identified 3 classes of patient change trajectories by using advanced statistical modeling of general distress outcomes across 5 to 25 sessions of therapy (average = 9.4 sessions). The largest class, representing 75% of clients, typified those who rapidly improved to session 5 and whose improvement plateaued to session 11, after which they improved again. This was called the “early and late change” class. The second largest class of patients, representing almost 20% of the sample, showed consistent linear change across the sessions. This was called the “slow and steady change” class. The third class of clients, representing about 5% of the sample, showed an initial decline in functioning up to session 5, followed by a steady improvement up to session 9, and then a plateau in improvement after session 9. This was called the “got worse before they got better” class. This last group of clients had the most severe symptoms at the outset.
This study indicates that one size does not fit all when it comes to how rapidly and in what manner patients change. “Early and late change” patients improve early on and then show another round of improvement later on in therapy. “Slow and steady” change patients show mild but consistent improvement across sessions of therapy. And those whose symptoms are more severe at the outset may “get worse before they get better”. This means that it may not be feasible to set an average fixed number of sessions for all patients, but rather therapists and agencies must rely on indices of reliable or good-enough change to determine optimal therapy length for each client. For example, “early and late change” patients may be working on different issues at different stages of therapy. Whereas clients who “show slow and steady” change may need to be in therapy longer before they realize sufficient improvement. For those patients with more severe symptoms who “get worse before they get better”, the therapy initially may be difficult but may ultimately induce change in the long run. In this case, therapists may need to provide enough of the current therapeutic approach before considering a change in the course of therapy.
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