Academic journal article Journal of Psychology and Christianity

Longitudinal Research on Psychotherapy Outcome: Recent Developments in Theories and Methodologies

Academic journal article Journal of Psychology and Christianity

Longitudinal Research on Psychotherapy Outcome: Recent Developments in Theories and Methodologies

Article excerpt

Howard, Kopta, Krause, and Orlinsky (1986) introduced a dose-effect model of psychotherapy outcome in which they attempted to specify the relationship between length of treatment (i.e., dos?) and patient benefit (i.e., effect). For the dose-effect model, the psychotherapy session is a natural quantitative unit of treatment with active ingredients, such as interpretation, homework assignments, and empathie reflection. It is assumed that the more sessions an individual has, the more active ingredients that individual has been exposed to (Kopta, Howard, Lowry, & Beutler, 1994). Howard et al. 's (1986) analysis, based on a meta-analysis of 2,431 patients from published psychotherapy outcome research spanning 30 years, found a positive association between dose and effect by a negatively accelerating curve with relatively diminishing returns later in treatment than early in treatment; that is the more psychotherapy, the larger the chance of improvement (Howard, et al., 1986; Lambert & Ogles, 2004).

Figure 1 demonstrates important features of the dose-effect model. The figure is from a study (Cornish & Wade, 2010) in which session-by-session outcome data of 1,353 college counseling center clients were analyzed using hierarchical linear modeling (HLM: Raudenbush & Bryk, 2002; Singer & Willett, 2003). Data for this study were collected by the Research Consortium of Counseling and Psychological Services in Higher Education during the academic semesters from 1997-1998. Before each individual counseling session, the client completed the Outcome Questionnaire (OQ-45: Lambert et al., 1996). The total score of the OQ-45 ranges from 0 to 180, with higher scores representing more frequent and more severe psychological distress, interpersonal problems, less adaptive social functioning, and less frequent positive emotional states. Cutoff scores of 63 and 64 were suggested to differentiate a non-clinical or functional population from a clinical or dysfunctional population (Hannan et al., 2005). The results indicate a strong negative overall growth trajectory with relatively diminishing returns in later treatment sessions than in early treatment sessions. The mean OQ-45 score at intake was estimated to be 70.93 and was highly significant, indicating on average the individuals in the sample have clinically significant issues. The average linear growth rate was negative (3.67) and highly significant, indicating in each session, clients on average improved by about 3.7 points on the OQ-45. The average quadratic growth rate (i.e., average rate of acceleration) was positive (0.1 6) and highly significant. These growth model coefficients show that, on average, clients were getting better each session, but at a decreasing rate over sessions. In the current sample, clients improved on average approximately 20 points from intake to session 10. More details of the study can be obtained from the author of this article.

Following Howard et al. (1986)'s seminal finding, a number of studies expanded the dose-effect model in psychotherapy. These studies compared treatment response rates for different psychological symptoms (Kopta, et al., 1994); tracked outpatients every week to determine the number of sessions required for a clinically significant change (Anderson & Lambert, 2001); or applied the model in the training clinic-setting (Callahan & Hynan, 2005).

In contrast, another line of research found no or at most, weak evidence of general dose-effect relationship. For example, Smith, Glass, and Miller, 1980, through their extensive meta-analysis, found only a weak curvilinear relationship between treatment outcomes and the duration of therapy. Talley (1992), observing 95 clients seen by 12 therapists at a university clinic, reported no relationship between treatment duration and clinical outcome. Salzer, Bickman, and Lambert (1999), analyzing 576 outpatient children, addressed the dose-effect relationship in child psychotherapy and found no evidence of a general dose-effect relationship. …

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