title: Dynamic models of individual change in psychotherapy process research.
abstract: OBJECTIVE
  There is a need for rigorous methods to study the mechanisms that lead to individual-level change (i.e., process-outcome research). We argue that panel data (i.e., longitudinal study of a number of individuals) methods have 3 major advantages for psychotherapy researchers: (1) enabling microanalytic study of psychotherapeutic processes in a clinically intuitive way, (2) modeling lagged associations over time to ensure direction of causality, and (3) isolating within-patient changes over time from between-patient differences, thereby protecting against confounding influences because of the effects of unobserved stable attributes of individuals. However, dynamic panel data methods present a complex set of analytical challenges. We focus on 2 particular issues: (1) how long-term trajectories in the variables of interest over the study period should be handled, and (2) how the use of a lagged dependent variable as a predictor in regression-based dynamic panel models induces endogeneity (i.e., violation of independence between predictor and model error term) that must be taken into account in order to appropriately isolate within- and between-person effects.
  
  
  METHODS
  An example from a study of working alliance in psychotherapy in primary care in Sweden is used to illustrate some of these analytic decisions and their impact on parameter estimates.
  
  
  RESULTS
  Estimates were strongly influenced by the way linear trajectories were handled; that is, whether variables were "detrended" or not.
  
  
  CONCLUSIONS
  The issue of when detrending should be done is discussed, and recommendations for research are provided. (PsycINFO Database Record
authors.affiliation: Centre for Psychotherapy Research and Education, Karolinska Institutet.
authors.forename: Fredrik
authors.identifier: 0000-0002-2486-6859
authors.initials: F
authors.lastname: Falkenström
authors.affiliation: Department of Political Science, University of Pittsburgh.
authors.forename: Steven
authors.initials: S
authors.lastname: Finkel
authors.affiliation: Department of Psychology, Lund University.
authors.forename: Rolf
authors.initials: R
authors.lastname: Sandell
authors.affiliation: Department of Psychology, University of Trier.
authors.forename: Julian A
authors.identifier: 0000-0002-9625-6611
authors.initials: JA
authors.lastname: Rubel
authors.affiliation: Department of Behavioral Sciences and Learning, Linköping University.
authors.forename: Rolf
authors.initials: R
authors.lastname: Holmqvist
mesh_terms: D006801:Humans; D007206:Individuality; D008137:Longitudinal Studies; D008960:Models, Psychological; D011369:Professional-Patient Relations; D013811:Psychotherapeutic Processes; D011613:Psychotherapy / Q000379:methods*; D012106:Research; D013548:Sweden