Patterns of symptomatology over time and their relation to outcome

The purpose of this study was to examine the association between characteristics of the symptomatology change curve (i.e., initial symptomatology, rate of change, and curvature) and final treatment outcome using a multilevel approach to account for therapist effects. The sample consisted of community clients (N = 492) seen by 204 student therapists at a training clinic. Linear, quadratic, and cubic trajectories of anxiety and depression symptomatology, as assessed by the Shorter Psychotherapy and Counselling Evaluation (sPaCE; Halstead, Leach, & Rust, 2007) were estimated. The multilevel quadratic trajectory best fit the data and depicted a descending curve (partial U-shaped). The quadratic growth parameters (intercept, slope, quadratic) were used as predictors of final treatment outcome as assessed by the Outcome Questionnaire-45.2 (OQ-45.2; Lambert et al., 1996). Patterns for two different successful outcomes, as conceptualised by (a) change in general symptomatology and (b) reliable improvement, were identified. For symptom change, successful outcomes followed a pattern of low initial levels of depression and anxiety, high initial rates of change, and high (flattening after initial drop) curvature, and the pattern applied to both within- and between-therapist levels. For reliable improvement at withintherapist level, successful outcomes followed a pattern of high initial rate of change and high curvature. For reliable improvement at between-therapist level, successful outcomes were associated with a pattern of low initial levels of depression and anxiety. Implications for clinical practice are discussed.