Randomized, Controlled Trial of the Effectiveness of Short-Term Dynamic Psychotherapy and Cognitive Therapy for Cluster C Personality Disorders

During the 5-year recruitment period, a total of 127 patients referred by two large psychiatric outpatient clinics, family doctors, and psychiatrists and psychologists in private practice were screened by an intake evaluator who was an experienced clinician and researcher. Patients were included if they were between ages 18 and 65 years and if they met the criteria for one or more DSM-III-R cluster C personality disorders or self-defeating personality disorder (which was included among the proposed diagnostic categories needing further study that were described in Appendix A of DSM-III-R). All diagnostic evaluations were audio- or videotaped and were performed by the intake evaluator with the Structured Clinical Interview for DSM-III-R (SCID-II) (11). A second diagnostician, an experienced clinical psychologist, reviewed a random sample of 20 SCID-II interviews. The combined agreement on the presence of one or more cluster C diagnoses and on the absence of any other axis II disorder was 0.77 (Cohen’s kappa). The patients who met the inclusion criteria and who did not meet the criteria for any cluster A or cluster B personality disorder returned within a week for a second diagnostic interview with the intake evaluator, who used the SCID-I interview to obtain DSM-III-R axis I diagnoses (12). Additional exclusion criteria were current or past psychotic disorder, current substance dependence or abuse, current eating disorder, organic brain disorder and other serious physical illness, active suicidal behavior, refusal to have the therapy sessions videotaped, and refusal to discontinue other active treatment. A total of 51 patients were included. After completing a number of self-report questionnaires and undergoing a psychodynamically oriented evaluation interview by a second evaluator, patients were presented with a full description of the study’s procedures, gave their written consent to participate, and were subsequently randomly assigned to receive 40 weekly sessions of either dynamic or cognitive therapy. Except for one patient who, in agreement with the therapist, terminated after childbirth midtherapy, all patients completed treatment in accord with the preplanned schedule of 40 sessions.

The demographic and clinical characteristics of the patients are shown in Table 1.

In both treatments, sessions were 50 minutes long, videotaped, and held once weekly. All therapists treated at least one patient as a training exercise before treating the patients who were enrolled in the study.

Systematic checks on the integrity and differentiability of the two treatments were performed by two independent raters (with 2 and 4 years of clinical experience, respectively) using the Inventory of Therapeutic Strategies (13). The Inventory of Therapeutic Strategies rates therapists’ interventions in terms of categories of intention (exploratory, supportive, or work enhancing), content, and object focus (e.g., therapist, others, self). Raters reviewed an entire early session (typically the sixth) and subsequently rated the frequency of Inventory of Therapeutic Strategies categories plus agenda setting and homework assignment. In analyses of data for categories that were rated reliably (r>0.65; range=0.65–0.83, mean=0.73), two-tailed t tests showed that short-term dynamic psychotherapy and cognitive therapy differed in their emphasis on supportive strategies (t=2.2, df=48, p<0.02; cognitive therapy had the stronger emphasis), work with defenses (t=4.0, df=48, p<0.001; short-term dynamic psychotherapy had the stronger emphasis), transference work (i.e., therapist as focus) (t=3.33, df=48, p=0.002; short-term dynamic psychotherapy had the stronger emphasis), agenda setting (t=9.9, df=48, p<0.0001; cognitive therapy had the stronger emphasis), and homework assignment (t=5.6, df=48, p<0.0001; cognitive therapy had the stronger emphasis). As for work enhancing strategies, the emphases were equally strong in the two treatments (t=0.03, df=48, p=0.50).

A measure of symptom distress was provided by the Global Severity Index of the SCL-90-R (14).

The total mean score of the full version (127 items) of the Inventory of Interpersonal Problems (15) was used to assess patients’ problems with assertiveness, intimacy, sociability, submissiveness, control, and responsibility for others.

The Millon Clinical Multiaxial Inventory (16), a 175-item questionnaire, was used to assess personality pathology as reflected by the cluster C personality disorder scales of avoidant, dependent-submissive, compulsive-conforming, and passive-aggressive, which have proved diagnostically efficient and congruent with DSM-III personality disorder diagnoses. Two Millon Clinical Multiaxial Inventory indices were computed: the total mean raw score on the four cluster C scales and the proportion of patients with a base rate score above 74, which represents the cutoff for “a prominent clinical syndrome” (16).

These measures were administered repeatedly during treatment and follow-up. See Table 2 for details regarding the timing of data collection.

Given our data collection design and our desire to include all available time-series data in our analyses, data from the SCL-90-R and Inventory of Interpersonal Problems were analyzed by using hierarchical linear models in order to utilize more fully the information inherent in the data (17). The hierarchical linear models that we used consisted of a within-patient and a between-patient model. The former (level 1) captured change over time for each patient plus termination status on the measures. The between-patient model (level 2) estimated the effect of treatment type on rates of change and status. At level 1, a two-piece linear model enabled us to capture rates of change during treatment and follow-up plus termination status for each patient. A two-piece model was chosen to allow for the analysis of the nonlinear change pattern exhibited by the plots of the patients’ time-series. In addition, we wanted to assess change and the effect of the two treatments in each of the two key phases. The analyses were conducted by using the HLM 5 computer program (18).

The Millon Clinical Multiaxial Inventory scores were analyzed by using paired t tests to assess change over time and by using independent t tests to compare the treatment effects at termination and 2-year follow-up. Since a hierarchical linear model normally requires at least three observations per patient, hierarchical linear model analysis was not considered an option for the Millon Clinical Multiaxial Inventory data. The Millon Clinical Multiaxial Inventory was not administered midtherapy because we reasoned that personality pathology would be less sensitive to change over the brief interval of 20 sessions.

On the basis of a two-tailed t test, an alpha of 0.05, and 25 patients in each group, power to detect a medium-sized effect (d=0.50) was 0.41 (19) for the comparison of short-term dynamic psychotherapy and cognitive therapy. Power to detect a large effect (d=0.80) was 0.79.

Means and standard deviations for the outcome measures are shown in Table 2 along with baseline equivalence results.

Essentially, clinically significant change has to do with the return to normal functioning (20). As defined in this study, clinically significant change occurs when 1) a patient moves from a dysfunctional population to a functional or normal population during treatment and 2) the magnitude of a patient’s change is statistically reliable. If a patient’s change meets both of these criteria, he or she is classified as recovered (20), i.e., as having returned to normal functioning.

On the basis of these criteria, patients are routinely categorized as 1) recovered (meeting both criteria), 2) as improved but not recovered, 3) as deteriorated, in the case of negative change (meeting the second criterion only), or 4) as unchanged (meeting neither criterion) (20). In this study, patient termination and 24-month follow-up scores were compared to scores for two functional or normal populations—a general community sample (21, 22) and a community sample of subjects who had been screened and found to be asymptomatic (23).

The percentages of patients in each of the four categories described in the previous paragraph are shown in Table 5. It appears that the percentages of patients who were unchanged or deteriorated at termination ranged from 60% to 71% (mean=62.5%) at termination of treatment and from 37% to 51% (mean=44.6%) at 2-year follow-up. Difference between the two means was significant (p<0.0001, z test). Among patients who recovered symptomatically (as measured by the SCL-90-R), it appears that at 2-year follow-up one of two short-term dynamic psychotherapy patients and two of five cognitive therapy patients were part of the general community population, while about two of five short-term dynamic psychotherapy patients and one of six cognitive therapy patients had joined the asymptomatic community population. As measured by the Inventory of Interpersonal Problems and the Millon Clinical Multiaxial Inventory, differences between groups in recovery rates were very small. As expected, relatively more patients returned to functional status (the general community population) than to asymptomatic status, and relatively more patients had recovered by 2-year follow-up than by treatment termination. As measured by the Millon Clinical Multiaxial Inventory, this latter difference was statistically significant for the short-term dynamic psychotherapy patients (p=0.002, z test; d=1.01) and approached significance for the cognitive therapy patients (p=0.053, z test; d=0.58).