A systematic review and meta-analysis of the good-enough level (GEL) literature.

The "good-enough level" (GEL) model proposes that people respond differentially to psychotherapy, and that the typical curvilinear "dose-response" shape of change may be an artifact of aggregation. We conducted a systematic review and meta-analysis of the GEL literature to examine (a) whether different subgroups of adults accessing psychotherapy respond to therapy at different rates and (b) whether the shape of change is linear or nonlinear. This review was preregistered on PROSPERO. Fifteen studies were synthesized (n = 114,123), with 10 included across two meta-analyses (n = 46,921; n = 41,515). Systematic searches took place using Medline, PsycINFO and Scopus databases. A key inclusion criterion was that cases must be stratified by treatment length to examine the GEL. In support of the GEL, there was no overall association between treatment duration and outcomes (r = -0.24, 95% confidence interval [CI: -0.70, 0.36], p = .27). Longer treatments were associated with higher baseline symptom scores (r = 0.15, 95% CI [0.08, 0.22], p < .001) and slower rates of change. Different shapes of change were also evidenced: Curvilinear responses were more often found in shorter treatments, while linear shapes were more often found in longer treatments. However, findings varied depending on methodological criteria used. Although rates of change varied in line with the GEL, most people nonetheless responded within defined boundaries as described in the dose-response literature. We therefore refer to the notion of "boundaried responsive regulation" to describe the relationship between treatment duration and outcomes. (PsycInfo Database Record (c) 2021 APA, all rights reserved).