Trajectories of change in weekly and biweekly therapy.

Higher therapy session frequency has been found to result in faster recovery, but few studies have considered that clients follow diverse trajectories of change in psychotherapy. It is unknown how session frequency may affect the sizes and shapes of change trajectories. The present study examined clients' change trajectories in weekly and biweekly therapy in a naturalistic setting, as well as predictors of these trajectories. Using a sample of 5,102 clients receiving 3-10 therapy sessions at a university counseling center, we identified 886 clients attending approximately weekly therapy and 1,753 clients attending approximately biweekly therapy. We examined the change trajectories of the weekly and biweekly samples using latent growth mixture modeling (LGMM). Three trajectories were identified in weekly therapy: slow change (78.33%), early improvement (17.61%), and worse before better (4.06%), and in biweekly therapy: slow change (80.38%), early improvement (13.52%), and worse before better (6.1%). The worse before better subgroup in weekly therapy experienced greater deterioration than those in biweekly therapy. The slow change and early improvement subgroups in weekly therapy showed treatment outcome comparable to those of their respective counterparts in biweekly therapy. Clients' intake symptoms, including eating concerns, frustration/anger, depression, and academic concerns, significantly predicted change trajectories. Compared to biweekly therapy, weekly therapy leads to higher chances of early improvement and shortens the duration of suffering but results in greater deterioration for individuals who deteriorate in therapy. The impact of session frequency on treatment outcome varies across clients, and session frequency should be adjusted individually. (PsycInfo Database Record (c) 2023 APA, all rights reserved).