
Department of Psychological Medicine, Christchurch School of Medicine and Health Sciences, Christchurch, New Zealand
Correspondence: Professor Sue Luty, Department of Psychological Medicine, Christchurch School of Medicine & Health Sciences, PO Box 4345, Christchurch, New Zealand. Tel: +64 3 3720 400; fax: +64 3 3720 407; email: sue.luty{at}chmeds.ac.nz
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Aims To compare the efficacy of interpersonal psychotherapy and CBT in people receiving out-patient treatment for depression and to explore response in severe depression (MontgomeryÅsberg Depression Rating Scale (MADRS) score above 30), and in melancholic depression.
Method Randomised clinical trial of 177 patients with a principal Axis I diagnosis of major depressive disorder receiving 16 weeks of therapy comprising 819 sessions. Primary outcome was improvement in MADRS score from baseline to end of treatment.
Results There was no difference between the two psychotherapies in the sample as a whole, but CBT was more effective than interpersonal psychotherapy in severe depression, and the response was comparable withthatfor mild and moder-ate depression. Melancholia did not predictpoor response to either psychotherapy.
Conclusions Both therapies are equally effective for depression but CBT may be preferred in severe depression.
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In the Christchurch Psychotherapy of Depression Study we compared IPT and CBT for depression. We predicted that both therapies would be equally effective in reducing depressive symptoms. We also predicted that both therapies would be less effective in severe or melancholic depression.
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Assessment
After being referred, patients were screened over the telephone by a
research nurse who confirmed depressive symptoms and checked inclusion and
exclusion criteria. Those who appeared suitable for inclusion were seen by a
psychiatrist, senior psychiatric registrar or clinical psychologist for an
initial assessment. After giving consent, the patient then attended for a
detailed clinical assessment. During this assessment participants were
administered the Structured Clinical Interview for DSMIIIR
(SCID; Spitzer et al,
1992), with an expansion of DSMIIIR and DSMIV
criteria for melancholic and atypical depression. Other clinician ratings were
the MontgomeryÅsberg Depression Rating Scale (MADRS;
Montgomery & Åsberg,
1979), the Hamilton Rating Scale for Depression (HRSD;
Hamilton, 1967) and the Mental
State Examination (MSE; Parker et
al, 1994). An independent research nurse completed the HRSD,
the MADRS and the MSE. This nurse also completed outcome assessments and was
therefore masked to the treatment allocation. Participants also completed a
series of self-report questionnaires which included the second edition of the
Beck Depression Inventory (BDIII;
Beck et al, 1987), the
Hopkins Symptom Checklist (SCL90;
Derogatis et al,
1973), the Structured Clinical Interview for Personality Disorders
Questionnaire (SCIDPQ; First et
al, 1997), and the Temperament and Character Inventory (TCI)
(Cloninger et al,
1994).
A neurobiological assessment was also included and blood was drawn for analysis of routine electrolytes, renal and hepatic function, blood glucose, blood count, thyroid function tests, a neuroendocrine assessment and DNA extraction. After this assessment, patients and therapists were advised as to whether the treatment would be either IPT or CBT. Patients were randomised to the two therapeutic interventions in a 1:1 ratio based on a computerised randomisation sequence of permutated blocks of size 20. Allocation of patients was performed by a person independent of the study.
Intervention
Following randomisation participants were booked to see their therapist on
an approximately weekly basis, for 50 min sessions for a period of up to 16
weeks. The minimum number of sessions allowed to fulfil the definition of
sufficient therapy exposure was 8 and the maximum was 19. The mean interval
between baseline and follow-up assessments was 13.75 weeks. The protocol
allowed for flexibility in the scheduling of appointments, including
twice-weekly sessions for patients who were initially severely depressed
and/or who had significant suicidal ideation, or less than weekly to allow for
marked improvement in depression or patient and/or therapist availability
(e.g. sickness, holidays). Following these weekly sessions, patients then
received 38 approximately monthly maintenance sessions over a further
period of 6 months. (The data presented here concern the outcome of therapy at
the end of the 16-week treatment phase.).
If at any stage of therapy there was deterioration in depressive or suicidal symptoms which interfered with the process of psychotherapy, or there was a sustained lack of improvement of severe symptoms for more than 46 weeks, patients could be seen for clinical review by a study psychiatrist. The decision to review was made during group discussions at supervision and was a joint decision based on Global Clinical Impression. At this stage patients would be offered adjunctive treatment with antidepressant medication if this was deemed necessary. If antidepressant medication was used or the patient was lost to follow-up, the last medication-free depression severity rating was used as the measure of efficacy for the intention-to-treat analysis (last observation carried forward). All therapy sessions were audiotaped for the purposes of treatment integrity ratings, and would also be used in supervision.
Cognitivebehavioural therapy
Cognitivebehavioural therapy was based on the manuals of Aaron and
Judith Beck (Beck et al,
1979,
1987). In this therapy the
therapist uses techniques related to the cognitive model of depression which
help the patient identify negative thoughts, views, assumptions and beliefs
about themselves, the world and the future that are related to their
depressive symptoms and functioning. The manual suggests session-by-session
guidelines, but, the therapy is tailored to meet each patients specific
needs in terms of pace and content. During early sessions the patient is
educated about depression and the cognitive model, and behavioural methods are
used to increase activity and facilitate cognitive change. In later sessions
the therapist helps the patient identify negative cognitions which they then
evaluate and substitute. In final sessions there is a focus on relapse
prevention. Techniques used within sessions include the Socratic method of
questioning, testing beliefs and assumptions, cognitive restructuring and use
of homework.
Interpersonal psychotherapy
Interpersonal psychotherapy was based on the manual by Klerman et
al (1984). This therapy
helps the patient identify and explore the social and interpersonal issues
that relate to and maintain their depressive symptoms. The patient and
therapist work together collaboratively and therapy is tailored to meet the
needs of each patient. As a general guide, in early sessions the therapist
develops an interpersonal inventory which details current and past important
relationships and asks questions to identify any of the four key problem areas
(grief, disputes, transitions and deficits) related to the depressive
symptoms. Once a focus is agreed upon from one of these problem areas, the
later sessions are used to help the patient develop strategies to deal with
the problem area. In final sessions there is a focus on terminating weekly
therapy. Techniques used to explore and change functioning include
communication analysis, problem-solving, affective exploration and
role-play.
Therapists
The five therapists in the study were psychiatrists, senior registrars or
clinical psychologists. Therapists had to have at least 2 years
experience of working with people with depression as out-patients and had to
treat at least two patients with both therapies, under supervision, to a
satisfactory level of competence before they were deemed eligible to treat
study patients.
Treatment integrity
Treatment integrity was monitored during the therapist training phase and
the study itself. Adherence and competence were the two main constructs
measured to ensure treatment integrity
(Waltz et al, 1993).
These measures ensured that the therapies were performed according to the
treatment manuals, and that the therapies were distinctly different from each
other, particularly since each therapist was conducting both forms of
treatment. Adherence has four components which refer to the extent to which
the therapist follows the psychotherapy protocol. These are the extent to
which the techniques used are:
The Collaborative Study Psychotherapy Rating Scale (CSPRS; Hollon et al, personal communication, 1984), which was developed specifically for use in the NIMH TDCRP to measure adherence, was used. The psychometric properties of the original 96-item version, which is able to distinguish between IPT, CBT and clinical management, have been described elsewhere (Hollon et al, personal communication, 1988). In our study the 96-item version was modified to distinguish distinguish between the two intervention therapies by omitting the 20 items pertinent to clinical management, reducing the scale to 76 items. Two postgraduate clinical psychology students were trained to use the CSPRS according to TDCRP recommendations (Hill et al, 1992). Analysis of CSPRS scores revealed that the therapists adhered to treatment protocols. Sessions were classified correctly 100% of the time and over 90% of these had strict adherence to protocol.
Competence refers to the extent to which the therapist responds appropriately to the patients problems with strategies relevant to the form of psychotherapy, and the quality of these strategies. To assess competence, two scales were used. The Therapist Strategy Rating Form (OMalley et al, 1988) was used to rate competence in IPT and the Cognitive Therapy Scale (Dobson et al, 1985) was used to rate competence in CBT. During training the supervisors each scored the competence scales according to the red line concept, which is an average acceptable score achieved for each therapist during training (Shaw, 1984). This was subsequently used quantitatively to ensure competence was maintained during the study phase.
Supervision
Supervisors were highly experienced in both therapies. Group supervision
was conducted throughout the training period and course of the study. During
these sessions the therapists and supervisors of each treatment met
fortnightly for 1.52 h. Supervision sessions followed similar formats
for each therapy with an emphasis on treatment integrity. Specific
difficulties encountered during therapy were addressed and general techniques
practised. Each new case was formulated according to the type of therapy. In
addition to the group supervision, individual supervision was conducted as
required.
To ensure interrater reliability, the supervisors also rated randomly selected audiotapes from each therapist during the study on a monthly basis. All ratings had acceptable supervisor agreement of 1 point on either competency scale, and all were above the therapists own predetermined red line.
Outcome variables
Outcome variables were defined a priori. The primary outcome
variable was percentage improvement in MADRS score, which is a robust measure
of change and allowed us to compare our findings with those of medication
studies (Mulder et al,
2003). The secondary outcome variable was response, defined as a
60% or greater change in MADRS score, and the five tertiary variables were
percentage improvement in HRSD score; percentage improvement in BDIII
score; percentage improvement in SCL90 score; and numbers of patients
achieving scores of 6 or below on HRSD, and/or 9 or below on the
BDIII.
Statistical methods
All analyses were performed on the intention-to-treat sample and the
statisticians were unaware of therapy allocation. Pre-intervention demographic
and clinical variables were compared between groups using independent
t-tests,
2 tests and (when frequencies were low)
Fishers exact test. The outcome change variables were compared between
groups using independent t-tests and
2 tests as
appropriate. A multiple linear regression, using dummy variables for
psychotherapy group, was used to test the hypothesis that pre-intervention
severity and melancholia influenced the relative efficacy of the two
interventions. This model included terms for the main effects of therapy,
baseline severity and melancholia and the two interaction terms
severityxtherapy and melancholiaxtherapy. The study was powered to
show a 15% difference in improvement on the MADRS, as this level was
considered a minimum clinically significant effect. A sample size of at least
85 in each therapy group provided more than 90% power to detect this
difference as statistically significant (two-tailed
=0.05) assuming a
within-group standard deviation of 30%.
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At the end of these weekly sessions 9 patients who received IPT and 5 who received CBT commenced taking antidepressant medication owing to lack of improvement. This resulted in 74 medication-free patients commencing monthly maintenance IPT and 71 such patients commencing monthly maintenance CBT (Fig. 1). The mean number of weekly sessions was 13, ranging from 8 to 19. Of the five therapists, two psychiatrists treated 39 patients each (one 21 IPT and 18 CBT, the other 26 IPT and 13 CBT), two clinical psychologists treated 45 patients each (one 22 IPT and 23 CBT, the other 18 IPT and 27 CBT), and one clinical psychologist joined the study late and treated 9 patients (4 IPT and 5 CBT).
![]() View larger version (23K): [in a new window] [as a PowerPoint slide] |
Fig. 1 Study profile.
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2=5.24, P=0.022). Although the finding is not
statistically significant, 16% of those randomised to IPT, compared with 24%
of those randomised to CBT, were classified as severely depressed, based upon
a previously defined cut-off score of 30 or more on the MADRS
(Muller et al,
2003). |
View this table: [in a new window] | Table 1 Baseline characteristics of the two therapy groups. |
Table 2 presents the primary and secondary outcomes for each therapy. A total of 159 patients (90%) completed at least eight sessions of weekly therapy, and 145 (82%) remained medication-free and commenced monthly maintenance therapy. On the primary outcome measure of percentage improvement on the MADRS there was no statistically significant difference between the two therapies (P=0.059). Overall improvement in depressive symptoms was about 55%. The difference between the two therapies was further examined using analysis of covariance to control for baseline severity; this was also not statistically significant (P=0.055). With a 9.5% mean difference in outcomes between therapies, the 95% confidence interval is -3.8% to 19.2%. If a 15% difference in outcomes between therapies is considered clinically significant, then with sample sizes of greater than 85 per group we had a 90% power to detect such a difference.
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View this table: [in a new window] | Table 2 Primary and secondary outcomes by therapy in the intention-to-treat sample |
On the secondary outcome measure, a categorical outcome of a 60% or greater improvement in MADRS score, there was again no statistically significant difference between therapies, with 92 (52%) being defined as responders. The 95% confidence interval on the 14% difference in response rate is 3.2% to 28.8%. Analysis of outcome was also performed using the five tertiary measures. Outcome was significantly better (P=0.046) in the group receiving CBT using percentage improvement in HRSD scores. However, HRSD categorical response was not significant. Neither dimensional nor categorical outcomes measured by BDIII were significant and there was no difference using the dimensional change in SCL90 scores (Table 3).
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View this table: [in a new window] | Table 3 Tertiary outcomes by therapy using intention-to-treat sample |
Table 4 shows the mean percentage improvement on the MADRS predicted by psychotherapy, severity and melancholia. Table 5 presents a multiple linear regression analysis of variables contributing to outcome. When percentage improvement is predicted from these variables severity x psychotherapy is a significant predictor (F=4.28, P=0.040) i.e. IPT is less effective in severe depression. Notably, neither melancholia nor melancholiaxpsychotherapy predicted poor response to treatment.
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View this table: [in a new window] | Table 4 Impact of baseline depression severity and melancholia on final MontgomeryÅsberg Depression Rating Scale scores, by psychotherapy |
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View this table: [in a new window] | Table 5 Multiple linear regression predicting percentage improvement using psychotherapy, baseline severity and melancholia |
Table 6 presents a
comparison between our findings and the NIMH TDCRP findings. Since the TDCRP
required higher HRSD scores for inclusion (
14), we included only those
patients who reached this cut-off point in our analysis. The TDCRP did not use
MADRS scores thus comparisons are presented for our tertiary measures only. It
is of note that we had slightly more patients than the TDCRP (128 v.
120) and a greater number of completers (116 v. 84), i.e. fewer
withdrawals from the study, although the TDCRP required patients to attend
more sessions to be deemed a completer (13 v. 8). Categorised by
therapy, we had fewer withdrawals from our CBT group (n=6; 9%) than
the TDCRP (n= 22; 37%). If we compare HRSD scores between studies, at
baseline we had slightly lower mean scores but similar end-of-therapy scores
were similar, although our patients who received CBT achieved much lower final
scores (i.e. were the less depressed group at outcome). We were unable to
compare our percentage of improvement in HRSD score, since the TDCRP used
adjusted treatment scores. If we compare scores by the TDCRP definition of
recovery (HRSD score of 6 or below), more of our CBT patients and fewer of our
IPT patients achieved this. We cannot make direct comparisons between the BDI
scores in each study since the TDCRP used the original version of this
measure, which differs in scoring from the BDIII, but scores are
presented for interest.
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View this table: [in a new window] | Table 6 Comparison with outcomes of the National Institute of Mental Health Treatment of Depression Collaborative Research Program |
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Psychotherapy for severe depression
Our hypothesis was that neither of the two psychotherapies would be
particularly effective in participants with severe depression. Using a
baseline MADRS score of 30 or more to categorise severe depression
(Muller et al, 2003),
which is more stringent than cut-off points of 20 on the HRSD or 30 on the
BDIII, we have reported that CBT is significantly superior to IPT in
this subgroup. Although the level of severity we chose may be on the lower end
of a clinicians experience of depression, we were unable to explore
outcome for those with higher MADRS scores since numbers were too small.
Despite the severe subgroup being only 20% (n=36) of
our sample, those receiving CBT had a better outcome than those receiving IPT
on both our primary dimensional outcome variable of percentage improvement and
our secondary categorical outcome variable of response. Only 20% of patients
with severe depression responded to IPT, whereas 57% of patients with severe
depression responded to CBT. Furthermore, this response rate of 57% to CBT in
severe depression compares favourably with the response to either type of
therapy in mild or moderate depression. Our study therefore adds important
data to the use of psychotherapy in severe depression. Our results contradict
the findings of Elkin et al
(1989), but are consistent
with reviews by McLean & Taylor
(1992), Shapiro et al
(1994) and DeRubeis et
al (1999), and do not
support the use of IPT for severe depression. We speculate that in severe
depression the early behavioural activation in CBT favours symptom resolution,
whereas the early exploratory approach of IPT hinders such resolution.
Psychotherapy for melancholic depression
Although we predicted that patients with melancholic depression would
respond poorly to psychotherapy, this subtype of depression was not associated
with poor outcome. This result challenges the notion that such patients should
be treated cautiously with psychological treatments and will only respond to
medication (Thase & Friedman,
1999). It should be noted that our participants with melancholia
were out-patients; in-patients might have had a different outcome. Our
findings certainly raise the possibility that patients with melancholia can
benefit from CBT and IPT.
Strengths and weaknesses of the study
This was an out-patient study, so to continue receiving psychotherapy
patients had to be willing and motivated, which might bias our findings for
patients with melancholia and severe depression. It is possible that our
therapists were particularly experienced, and the supervisory process allowed
for support and encouragement in managing difficult aspects of therapy which
contributed to the positive outcome in these patients.
This is the largest trial ever conducted comparing these two psychotherapies for depression. The trial was conducted within a university-based out-patient clinical research unit, and patients were not sought by advertising. Despite the relatively young age of the sample, over two-thirds had chronic (i.e. more than 2 years of depression in the past 5 years) and/or recurrent depression. Our clinical research unit has previously undertaken trials of antidepressant medication (Joyce et al, 1994, 2002), but during this psychotherapy trial we were not simultaneously involved in any antidepressant studies so that there was no inclination to exclude severely depressed patients from this study and enter them into an antidepressant trial. During the trial only seven patients were prescribed antidepressants, which indicates a willingness, but seldom a need, to use these as alternative therapy. Conversely, we did not require a minimum score on the MADRS or HRSD for entry into the study, just that patients met DSMIV criteria for a major depressive episode. Thus, we have included milder cases of depression, which were typically excluded from earlier studies such as the TDCRP. We therefore have the full range of out-patient depression severity within our sample.
During this study just five therapists in a single setting undertook all the therapy. Two were psychiatrists and three were clinical psychologists. The two psychiatrists commenced with prior training in and thus possible allegiance to IPT, and required training in CBT; the three clinical psychologists began with prior training in and thus possible allegiance to CBT and required training in IPT. When outcomes were examined according to therapist, there was no significant outcome effect due to therapist, professional training or prior experience of each therapy. The fact that the therapists were required to deliver both therapies, and had supervision to ensure that they were adhering to the specific therapy, argues against therapist effects having influenced our results.
In conclusion, IPT and CBT were comparable short-term out-patient psychotherapies for major depression, despite each having different models and techniques. Cognitivebehavioural therapy was superior in patients with severe depression, and this is further evidence that this therapy (but not IPT) might be a reasonable first-line treatment option for severe depression. It is noteworthy that patients with melancholia responded equally well to both psychotherapies. This suggests that patients with melancholia who want psychotherapy should not be denied it, as it is a potentially effective treatment option.
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