Comparing Short- and Long-Term Group Therapy: Seven-Year Follow-Up of a Randomized Clinical Trial
Authors: Steinar Lorentzen, Anette Fjeldstad, Torleif Ruud, Per A. Høglend
Journal: Psychotherapy and Psychosomatics (2015)

Many mental disorders have a recurrent course [1], and information about the long-term effects of treatment are highly desirable [1,2]. Maintenance of gains is reported from a number of controlled studies [3], but systematic information about true delayed effects (after treatment termination) is sparse [1,2]. In this clinical trial, 167 outpatients with mixed diagnoses were randomized to 20 or 80 weekly 90-min sessions of short- (STG) or long-term (LTG) group analytic therapy. The patients had experienced recurrent problems for 11 years (median), had 3.3 (±2.0) DSM-IV axis I diagnoses, and 68% had been in therapy at least once before. We previously reported that patients in both treatments had equal changes in symptoms and interpersonal problems over a 3-year period [4]. Here, we report the 7-year (from baseline) follow-up and hypothesize that LTG patients will improve significantly more during the last 4 years than STG patients. This study was registered at ClinicalTrials.gov as NCT00521417, August 24, 2007.Inclusion criteria were one or more DSM-IV axis I or II diagnoses and interest in working on dysfunctional relationships in a group setting. Exclusion criteria were psychosis, alcohol/drug addiction and organicity [4]. The patients' mean age was 38.4 (±9.4) years, 63% were women, and 45% were single. The mean duration of education was 13.7 (±3.2) years and there was high comorbidity with affective (83%), anxiety (60%), and personality disorders (48%), mostly cluster C. Eighteen groups (9 STG and 9 LTG), each including 7-8 patients and 1 therapist, were established. The therapies were manualized and built on psychodynamic understanding, entailing a developmental perspective on personality, the existence of internal representations of interpersonal relationships, psychological causation, and that unconscious individual and group processes strongly influence overt behaviour [5]. Nine experienced therapists each conducted 1 STG and 1 LTG. The two much used and well-validated self-report outcome measures were Symptom Checklist-90-Revised (SCL-90-R) and the Inventory of Interpersonal Problems-Circumplex (IIP-C), with 90 and 64 items, respectively. The Global Severity Index (GSI; mean of SCL-90-R) measured symptomatic distress and the mean IIP-C measured interpersonal problems [4]. The evaluation included a full psychiatric record and diagnostic interviews. The SCL-90-R and IIP-C were administered 7 times (every 6 months from baseline to 24 months, then at 36 and 84 months), and it was also completed by most non-starters and premature withdrawals. Selected sessions from both therapies were audio-recorded.We used linear mixed models to analyse longitudinal data, which can handle incompleteness due to missing data and allow non-independence of repeated and nested data [6]. A 2-piece linear model with the knot at 36 months fitted the data better than a 1-piece linear model. The relevant parameter is the treatment effect, time × group length, which is the difference in slopes between LTG and STG during the last 4 years of the study period. Effect sizes (ES; converted to Cohen's d), derived from the F test for mixed effects model, were calculated aswhere F is the F test statistic for the effect of interest in the repeated model and d.f. the degrees of freedom.Treatment adherence was confirmed by 2 independent raters blindly rating 39 sessions (of a pool of 54), including both STG and LTG, on therapist activity level, degree of focus, group work in the here-and-now and therapist competence. Intraclass correlation coefficients on therapy process ranged from 0.70 to 0.94. There were significantly more frequent mentioning of 'a circumscribed focus' and occurrence of episodes of 'work in the here-and-now' in STG than in LTG, as suggested in the treatment manuals. Therapist activity (the time a therapist spoke in the sessions), however, was equal in the two formats. The therapists' mean competence was moderate to high, and similar in both therapies. Withdrawals after randomization (19 patients) were similar in LTG and STG, but there were more premature terminations (within the first two thirds of the therapies) in LTG. Evenly distributed terminations in LTG and STG indicated that the higher number of withdrawals in LTG (33 vs. 9%) was due to the longer duration of LTG. Seventy-nine LTG patients (88%) and 71 STG patients (92%) completed the 3-year follow-up interview. At 7 years, 72% of the LTG patients and 74% of the STG patients participated.The dependency in the data within groups and therapists on the GSI and IIP-C was negligible (all intraclass correlation coefficients were <0.01). From year 3 to the 7-year follow-up, there was a non-significant difference in GSI change in favour of the LTG: B = -0.002, F(1, 118) = 2.2, p = 0.14, ES = 0.3. Because of skewness in the data, we used bootstrapping (n = 1,000) for estimates of fixed effects, which yielded p = 0.03. For the IIP during the same period, there was a significant difference in change in favour of the LTG: B = -0.003, F(1, 120) = 5.3, p = 0.02, ES = 0.4. We did a comparison with a completer case analysis (participants with data at follow-up), and the patterns of change were similar. We also included completer status × time × group length in the statistical model, B = 0.0003, F(1, 116) = 0.02, p = 0.90. This suggests that the parameter estimates generated by the original model are valid and not biased by missing data. The differences in group changes are shown in figure 1.At the 7-year follow-up, 32% of patients in the STG and 41% in the LTG achieved a clinically significant change (recovery) for GSI. The corresponding numbers for the IIP were 35 and 49% [7]. We have previously reported no significant differences in the use of additional therapy (admissions, general practitioner, psychiatric nurse, physiotherapist, psychiatrist/psychologist, medication) during the first 3 years [4]. This may be expected since both treatments worked equally well during this study period. At the 7-year follow-up by mail, we feared that a detailed questionnaire might give a lower response rate, and did not include questions on additional therapy during the last 4 years.Our hypothesis concerning a delayed change in symptoms and interpersonal problems in the LTG compared with the STG was confirmed. A difference in therapy effect was most convincing for IIP, but also present for GSI, as there was a small ES (0.3) in favour of LTG.Psychodynamic theories outlined in the treatment manual suggest that change may be brought about by an increased understanding of the internal world of self and others (insight) [5]. Prominent theoreticians have maintained that change takes place more readily in longer-term therapy, since it offers considerably more opportunities for corrective emotional experiences, for working through old dysfunctional patterns and trying out new, more constructive interpersonal behaviours [8]. However, we believe this is the first study that shows this empirically, by comparing psychodynamic groups of different lengths directly within the same study. We have previously found that punitive and harsh self-introjects change more in LTG than STG [9]. Recent studies comparing psychodynamic therapies of different length and intensity indicated that long-term therapy was more favourable than short-term therapy with regard to depression and interpersonal functioning [2,3,8,10].Strengths of the study were design, long-term follow-up, high participation rates and control of therapy adherence and therapist competence. A limitation is lack of information about additional treatment during the last 4 years. Intuitively, it seems plausible that STG patients would more often receive additional treatment. Therefore our results do probably not overestimate the treatment effects.The study was partly funded by a grant from the Regional Health Authority South-East, partly from Oslo University Hospital and the University of Oslo.There are no conflicts of interest.