Separating the effects of improvements and deteriorations in mechanisms on outcome using the asymmetric effects model

The aim of this article was to introduce the Asymmetric Fixed Effects (AFE) model to psychotherapy mechanisms of change researchers as a novel way of studying the effects of improvements and deteriorations in the candidate mechanism(s) separately. Alliance-outcome research was used to illustrate the possibility of estimating separate effects of improvements and deteriorations in the alliance.

Two archival data sets were used. One was from community-based primary care services in Sweden using the Clinical Outcomes in Routine Evaluation-Outcome Measure (CORE-OM) and the Working Alliance Inventory-Short form (WAI-S, therapist form) each session with 1,096 patients. The other data set was from a university counseling center in China using the Session Rating Scale (SRS) and the Outcome Rating Scale (ORS) each session with 292 patients. Data were analyzed using the AFE model.

The findings indicated that with raw scores, improvements in alliance from one session to the next were followed by lower symptoms/distress scores by the next session, but alliance deteriorations had no effect on next-session symptoms/distress. With alliance deteriorations and improvements defined relative to the sample's average linear change over time, improvements, and deteriorations had equal but opposite effects on next session symptom level.

Findings confirm the utility of the Asymmetric Fixed Effect model across two cross-national samples in showing that alliance deteriorations and improvements can predict next session symptoms separately at the within-person level. Findings raise new questions regarding the use of detrending in within-patient mechanism of change studies. (PsycInfo Database Record (c) 2021 APA, all rights reserved).