Comparative efficacy of cognitive behavior therapy and interpersonal therapy in the treatment of depression: A randomized controlled study

Abstract

Background:

Depressive disorders are one of the most common psychiatric disorders that occur in people of all ages.

Aim:

To assess the efficacy of cognitive behavior therapy (CBT) and interpersonal therapy (IPT) in cases of depression.

Materials and Methods:

The sample for the study comprised 52 diagnosed cases of major depressive disorder (MDD) based on the 10^th revision of the International Classification of Diseases (ICD-10) criteria in the age range of 21 to 50 years. They were randomized with the help of the app and assigned to CBT and IPT groups. Two patients had dropped out of the CBT group. Hence, finally, 50 cases were taken for study. A total of 12 therapy sessions were given. All patients were given standard treatment as prescribed.

Results:

Findings of paired samples t-test to assess the within-group differences in both the groups (CBT and IPT) as well as gains score statistics or difference score statistics (pre-test minus post-test) were applied to compare group differences. Results of paired samples ‘t’ test suggest that there was a statistically significant difference in the scores of both the groups from pre-test to post-test. IPT group had shown significantly better outcomes as quantified by the percentage of patients scoring less on the outcome variable of the Beck Depression Inventory (BDI), Montgomery–Asberg Depression Rating Scale (MADRS), Hopelessness Scale, and General Health Questionnaire (GHQ).

Conclusion:

Both CBT and IPT are efficacious in the treatment of MDD. IPT yielded better results on MADRS as compared to CBT on parameters of outcome in the present study. The findings indicate that interventions were effective in reducing the symptoms of depression.

Depressive disorders are one of the most common psychiatric disorders that occur in people of all ages across all world regions. Depression as a disorder has always been the focus of attention of researchers in India. Over the past 50–60 years, a large number of studies have been published from India addressing various aspects of this commonly prevalent disorder.[1] Depression is a significant contributor to the global burden of disease and affects people in all communities across the world. Globally, the burden of depression has been rising, and major depressive disorder (MDD) was the third leading cause of disability in 2015.[2] The onset of depressive disorders starts early by affecting functioning at a young age. Hence, depression is considered to be the leading cause of disability worldwide in terms of total years lost due to disability. It is important to emphasize the management of depression and create awareness regarding depression. Published data on the global prevalence of depressive episodes varies from 3.2 to 4.7%.[3] World mental health survey ranged from 0.8 to 9.6% across countries.[4] In fact, by 2030, unipolar depression is predicted to be the second leading contributor to the global burden of disease.[5] MDDs accounted for around 8.2% of global years lived with disability (YLD), and it was the second leading cause of the YLDs. In addition, they also contribute to the burden of several other disorders indirectly, such as suicide and ischemic heart disease.[6] Studies conducted in high-income countries reported a significantly increased risk of depression/mood disorder in urban when compared with rural areas.[7] The prevalence rate of mood disorder was estimated to vary from 0.5 to 78 per 1,000 population.[8] Previous epidemiological studies on depression in India have been conducted using differing methodologies, sample sizes, sampling techniques, study instruments, case definitions, and different study populations at different periods.[9] The available data is variable in terms of estimates of depression prevalence in the country. The importance of evidence-based interventions and cost-effective treatment options are available to reduce the burden of depression.[10] The major depressive episodes are treatable in 70–80% of patients. The treatment of depressive disorders includes pharmacotherapy with psychotherapeutic interventions.[11] The effectiveness of intervention in cases of depression in primary care settings has also indicated that patients in the intervention group had better outcomes at 6 months than patients in the control group. It also concurred that psychological interventions play an important role in the recovery of patients from depression.[12]

Cognitive behavior therapy (CBT) has emerged as a leading evidence-based psychological therapy for depression. A meta-analysis of 115 studies has also yielded results showing that CBT is an effective treatment strategy for depression and combined treatment with pharmacotherapy is significantly more effective than pharmacotherapy alone.[13] Among other psychotherapeutic interventions, IPT has also been effective in reducing the severity of depression. Studies have reinforced the efficacy of IPT for major depression.[14] IPT is a time-limited, interpersonally focused, psycho-dynamically informed psychotherapy that has the goals of symptom relief and improving interpersonal functioning. IPT is concerned with the “interpersonal context,” and the relational factors that predispose, precipitate, and perpetuate the patient’s distress.[15] The evidence of the same is lacking in the Indian scenario, especially the evidence of the outcome of intervention of these two approaches. In this background, a randomized control study was undertaken to assess the efficacy of CBT in comparison with IPT in cases of depression.

MATERIALS AND METHODS

This study was carried out in the psychiatry department of a tertiary care center attached to a medical college. A sanction from the Institutional Ethical Committee was obtained before starting the study. Written informed consent was obtained from all the participants.

Study Design: It was an experimental study design, and therapy was considered to be an independent variable. Improvement in scores on the Beck Depression Inventory (BDI) was taken as the dependent variable. A score of <9 on BDI was a predictor variable.

Sampling Frame: Diagnosed cases of major depression meeting inclusion and exclusion criteria were part of the study. They were diagnosed by two independent clinicians based on the 10^th revision of the International Classification of Diseases (ICD-10) criteria.

Sampling Technique: Simple randomization was used. Equal numbers of patients were allocated to the CBT group and IPT group. The randomization method used was based on odd and even numbers generated through the app. Even numbers were assigned to CBT, and odd numbers generated were assigned to IPT. The random number generator app is a tool available for research and scientific endeavors. It employs advanced algorithms to ensure the utmost precision in randomness. The use of robust algorithms guarantees the elimination of biases, making it ideal for creating random assignments in experiments, clinical trials, and statistical analysis.

Sample Size Calculation: It is assumed that 57% of cases in the CBT group and 20% of cases in the IPT group will benefit through the intervention. Sample Size was calculated for comparing two treatment groups with the following specifications: α = 0.05; (1− β) = 0.80; π1 = 57%; π2 = 20%; n = 26.

Sample

The sample for the present study comprised 52 diagnosed cases F32.1: MDD, single episode, moderate. based on ICD-10 criteria. The duration of the study was 2 years. The selection criteria for the study population are given below.

Inclusion Criteria: Diagnosed cases of MDD based on ICD-10 criteria in the age group of 21–50 years

Exclusion Criteria: Patients with severe depression with psychotic features, head injury, and any other psychiatric co-morbidity were excluded.

Procedure

The sample comprised 52 diagnosed cases of depression hospitalized at a tertiary care center and patients reporting to the outpatient department (OPD). Psychological therapy in a structured format was given based on the principles of CBT and IPT to the study groups for 6–8 weeks. A total of 12 sessions were given to the participants in both groups. The cases were randomized with equal allocation in each group. They received CBT and also standard treatment as given routinely. The effect of the CBT was compared with the IPT. They were assessed before starting the intervention and after the intervention on clinical scales. A score of <9 on BDI, a score of <2 on GHQ, and a score of <6 on MADRS were taken as criteria for improvement. The following tools were administered:

• Demographic and clinical data sheet

• Beck’s Depression Rating Scale[16]

• Montgomery–A sberg Depression Rating Scale (MADRS)[17]

• General Health Questionnaire (GHQ)[18]

Interventions

Interpersonal Psychotherapy: There are five distinct phases in the IPT approach. The first one is the assessment phase, catering to the initial sessions, followed by middle sessions, termination sessions or the conclusion of acute treatment, and maintenance sessions. The IPT protocol followed the guidelines of Klerman and colleagues.[19]

Cognitive Behavior Therapy: Cognitive theory conceptualizes that people are not influenced by the events but rather by the view they take of the events. It essentially means that individual differences in the maladaptive thinking process and negative appraisal of life events lead to the development of dysfunctional cognitive reactions. This cognitive dysfunction is, in turn, responsible for the rest of the symptoms in the affective and behavioral domains. The CBT protocol was based on the manual by Beck and colleagues.[20]

Statistical Analysis

Quantitative data was analyzed with the Statistical Package for the Social Sciences 21 (SPSS 21; IBM, Amrock, USA). Descriptive analysis along with the paired samples t-test was used to assess the within-group differences in both the groups (CBT and IPT), as well as gain score statistics or difference score statistics (pre-test minus post-test) was used to compare group differences.

RESULTS

In the present study sample comprised of a total of 50 subjects. Initially, 52 cases were enrolled in the study; however, 2 cases from CBT dropped out of the study. The mean age of the sample was 33 and 36 years, respectively, in the CBT and IPT groups. 69% of the cases are married in the CBT group, and 58% of cases are in the IPT group [Table 1]. In the IPT group, a higher percentage of noncordial relationships was noted to be present. The study groups were assessed before starting the intervention and after the intervention on clinical scales. Treatment consisted of 16 to 20 individual 45-minute sessions.

Table 1.

Demographic details for the intervention group (CBT and IPT)

	CBT group (n=26)	IPT group (n=26)
Age
Mean	32.58	36.25
Gender
Male	50%	54%
Female	50%	46%
Marital status (%)
Married	69	58
Unmarried	31	42
Relationship status
Cordial	84	71
Noncordial	16	29
Education
Primary	23	45
12th	53	12
Graduation	11	37
Postgraduation	11	6

CBT=Cognitive behavior therapy, IPT=Interpersonal therapy

The following section describes the results of quantitative analysis done to assess the hypotheses regarding the effectiveness of CBT versus IPT interventions on general health, depressive symptoms, and hopelessness. Both groups were assessed on the pre-test level (before the intervention). After the pre-test, groups participated either in the CBT intervention or IPT. After the intervention, groups were re-assessed at the follow-up. Table 2 depicts the descriptive statistics for both groups.

Table 2.

Descriptive statistics of outcome variables of CBT and IPT groups across time levels

Outcome Variables	CBT Group (n=24) Mean±SD		IPT Group (n=26) Mean±SD
	Pre	Post	Pre	Post
GHQ BDI MADRS Hopelessness	5.58±1.65	0.92±0.74	4.64±1.65	1.13±0.85
	19.88±5.90	8.12±2.56	22.63±6.30	7.13±2.52
	19.38±5.07	7.46±2.32	32.46±5.34	6.96±4.21
	9.42±2.89	10±2.24	2.88±1.03	2.21±0.83

BDI=Beck Depression Inventory, CBT=Cognitive behavior therapy, GHQ=General Health Questionnaire, IPT=Interpersonal therapy, MADRS=Montgomery–Asberg Depression Rating Scale, SD=Standard deviation

To assess the normality distribution of the variables across the groups, the Shapiro–Wilk test was carried out. Results of the normality tests (Shapiro–Wilk) indicated that both the groups were normally distributed across variables (GHQ, BDI, MADRS, and Hopelessness). Thus, to assess the effectiveness of the intervention, parametric tests (paired sample ‘t-test’ and gain score ‘t-test’) were used. To assess the effectiveness of interventions in improving the symptoms, from pre-test to post-test, paired samples t-test was calculated [Table 3]. To compare the effectiveness of both groups, gain score analysis on the differential scores was used [Table 4]. Figures 1 to 4 depict the graphical representation of the gain score analysis on each outcome variable.

Table 3.

Within-group analysis

Variables	Mean	Standard deviation	t	Sig. (2-tailed)
GHQ	4.060	1.596	17.987	0.000**
BDI	13.560	5.859	16.364	0.000**
MADRS	18.440	8.716	14.960	0.000**
Hopelessness	7.140	2.232	22.624	0.000**

BDI=Beck Depression Inventory, GHQ=General Health Questionnaire, MADRS=Montgomery–Asberg Depression Rating Scale. **Significant at 0.005 level

Table 4.

Gain score analysis

Variables	Groups	n	Mean	t	Sig. (2-tailed)
GHQ	CBT	26	4.65	2.945	005**
	IPT	24	3.42
BDI	CBT	26	11.77	-2.35	0.02*
	IPT	24	3.42
MADRS	CBT	26	11.92	-0.8.81	000**
	IPT	24	25.50
Hopelessness Scale	CBT	26	6.5385	-2.04	0.46*
	IPT	24	7.7917

BDI=Beck Depression Inventory, CBT=Cognitive behavior therapy, GHQ=General Health Questionnaire, IPT=Interpersonal therapy, MADRS=Montgomery–Asberg Depression Rating Scale. *Significant at 0.05 level, **Significant at 0.005 level

Figure 1.

Mean difference in variable GHQ across CBT and IPT. CBT = cognitive behavior therapy, GHQ = General Health Questionnaire, IPT = interpersonal therapy

Figure 4.

Mean difference in variable Hopelessness across both the groups

Within-group Analysis

Results of the paired sample ‘t’ test suggest that there was a statistically significant difference in the scores of both the groups from pre-test to post-test. This indicates that the scores on all the variables showed significant improvement from the pre-test to the post-test, suggesting that the interventions were effective in reducing the symptoms of depression and hopelessness. It also indicates that there was overall improvement in general psychological health (as measured by GHQ), after the intervention. To compare the effectiveness of the intervention and understand which intervention was more effective, a gain score ‘t-test was employed. The results are discussed below.

Gain Score Analysis

Results indicate that both groups significantly differed in the gain scores obtained across all the variables. Figures 1 to 4 show the comparison of both groups based on the mean difference obtained by subtracting post-test scores from the pre-test scores. Inspection of the mean difference suggests that IPT was more effective as compared to CBT in improving the scores on measures of BDI, MADRS, and hopelessness. All three variables mainly assess the symptoms related to depression. Whereas, CBT was comparatively more effective in improving the scores of general well-being. Figure 1 indicates that the mean difference score on GHQ was higher for the CBT group as compared to the IPT group. Figure 2 indicates that the mean difference score on BDI was higher for the IPT group as compared to the CBT group. Figure 3 indicates that the mean difference score on MADRS was higher for the IPT group as compared to the CBT group. Figure 4 indicates that the mean difference score on hopelessness was higher for the IPT group as compared to the CBT group.

Figure 2.

Mean difference in variable BDI across both the groups. BDI = Beck Depression Inventory

Figure 3.

Mean difference in variable MADRS across both the groups. MADRS = Montgomery–Asberg Depression Rating Scale

Qualitative Analysis

To assess the overall effectiveness of each intervention (CBT and IPT), the percentages of the sample population having scores <2 (for GHQ), <9 (for BDI), and <6 (for MADRS) at post-test assessment were calculated. Results indicate that in both groups, 100% of participants scored <2 on the GHQ measure. In the case of BDI, 79% of the participants from the IPT group and 76% from the CBT group scored <9, indicating that the number of participants meeting the criteria of improvement was more in the IPT group than in the CBT group. Similar findings were found in MADRS. In the IPT group, 54.16% of participants met the improvement criteria, as compared to 42% of participants meeting the criteria in the CBT group. The study was aimed at assessing and comparing the effectiveness of CBT versus IPT on improving overall mental health (measured by GHQ), depressive symptoms (measured by BDI, MADRS), and hopelessness in a sample of 50 participants. The study groups were assessed before starting the intervention and after the intervention on clinical scales. A score of <9 on BDI, a score of <2 on GHQ, and a score of <6 on MADRS were taken as criteria for improvement [Figure 5].

Within-group analysis showed that both groups showed significant improvement in all four measures from the pre-test to the post-test [Table 3].

To compare the effectiveness of both interventions, an independent-sample t-test was run on the gain score (pre-test and post-test) to determine if there was a mean difference in the scores of GHQ, BDI, MADRS, and Hopelessness. The results indicate that both the groups differed significantly on all the variables.

There was a statistically significant increase in the scores of the IPT group on the following variables: BDI, MADRS, and Hopelessness. IPT group showed more improvement on these measures, suggesting that IPT intervention was efficacious [Table 4]. CBT was more effective in improving the scores of GHQ.

The sample with <2 scores on GHQ, <9 on BDI, and <6 on MADRS were taken as the outcome variables. The post-therapy intervention GHQ scores in both IPT and CBT groups were noted to be <2. The mean score on BDI is noted to be <9, and the score on MADRS is around 6 in the IPT group. From the results of the study, it can be concluded that GHQ scores were reduced significantly in the CBT group. Whereas scores in the IPT group had reduced significantly on BDI, MADRS, and Hopelessness, which primarily reflect improvement in depressive symptoms. As far as the comparison of the outcome variable is concerned, it is noted to be significantly better in the IPT group; that is, the outcome is noted to be in 79% of cases and improvement in BDI in the IPT group and 76% in CBT group respectively (scores <9 on BDI). Whereas on MADRS, 54.16% reported improvement in the IPT group, and 42% of cases reported improvement in the CBT group. If we take a cut-off of two on GHQ as the criteria, the majority have shown improvement.

The lowest figure is 42%, and the highest is 79% of cases as far as outcome defined as per criteria is related to outcome variable [Table 5]. The parameter of depression as an outcome variable is comparable in both groups, and there seems to be significant improvement in the group receiving either CBT or IPT.

Table 5.

Percentages of participants having scores <2 (for GHQ), <9 (for BDI), and <6 (for MADRS) at post-test assessment across the treatments

Scales	Groups
	CBT	IPT
GHQ	100%	100%
BDI	76%	79%
MADRS	42%	54.16%

BDI=Beck Depression Inventory, CBT=Cognitive behavior therapy, GHQ=General Health Questionnaire, IPT=Interpersonal therapy, MADRS=Montgomery–Asberg Depression Rating Scale

DISCUSSION

The study was aimed at assessing and comparing the effectiveness of CBT versus IPT on improving overall mental health (measured by GHQ) and depressive symptoms (measured by BDI, MADRS, and Hopelessness) in a sample of 50 participants. Pre-test (before the intervention), all the patients were evaluated by the above tools, and then they were administered CBT and IPT along with their medications. After the intervention, groups were re-assessed at the follow-up level. Comparison in both the group’s pre and postintervention revealed improvement in GHQ scores below two in both groups. There was a statistically significant difference in the scores of both the groups from pre-test to post-test evaluation. This indicated the improvement in all the variables after therapy (CBT, IPT) was instituted. This suggested that the interventions were effective in reducing the symptoms of depression and hopelessness. Results indicate that IPT was more effective as compared to CBT in improving the scores on BDI, MADRS, and hopelessness. Whereas, CBT was comparatively more effective in the scores of GHQ. The comparison of intervention between CBT and IPT is not very conclusive. This concurs with the published literature. Meta-analysis comparing the CBT and IPT studies found that differences in treatment efficacy between CBT and IPT for MDD vary according to outcome measure. CBT shows an advantage over IPT for MDD according to BDI, although there is no significant difference according to HRSD. There seem to be variable differences in the findings. The study concluded that future research should be conducted with a low risk of bias, more kinds of outcome measures, more standard interventions, and longer follow-up.[21]

What is worth mentioning here is that the difference between the two approaches is primarily the way symptoms are addressed. CBT attempts to correct distorted views and maladaptive beliefs that can give rise to depression; it works on reducing depression. On the other hand, IPT focuses on helping patients improve the quality of their relationships associated with depressive symptoms. This approach helps in solving interpersonal problems. Improvement in the interpersonal domain leads to satisfaction in handling relationships, and distress is reduced. Hence, if we look at the outcome variable, there may be some differences between the two therapies, but the outcome is a reduction in distress aimed by both approaches.

There are findings on the contrary that the efficacy of either therapy is noted to be comparable.[20] CBT and IPT also share several common features: both are time-limited, symptom-targeted, and present-focused and encourage the patient to regain control of mood and functioning. Furthermore, both try to increase the patient’s activity level and pay special attention to the identification of expectations and assumptions using interventions such as exploration and clarification.[21] In addition, both therapies emphasize the importance of other (nonspecific) factors such as structure, motivation, and alliance. The difference was noted more on the BDI score as compared to the MADRS score. This could be because items are different.

This systematic review compared IPT and other standard methods of psychotherapy for the treatment of major depressive disorder (MDD) in adult outpatients.[22] Results unfolded interestingly that out of 1233 patients included in eight eligible studies, 854 completed treatments in outpatient facilities. IPT combined with pharmacotherapy improved depressive symptoms significantly better than pharmacotherapy alone. Depressive symptoms were reduced more in CBASP (cognitive behavioral analysis system of psychotherapy) patients in comparison with IPT patients, while IPT reduced symptoms better than usual care and waitlist condition. CBT and IPT are advised for the treatment of depressive disorders apart from regular drug treatment. IPT was originally developed for treating acute depression by improving interpersonal functioning with important others.[23] Several reviews have indicated IPT to be an effective treatment for depression.[24,25,26] Reviews and meta-analyses have highlighted the role of IPT to be effective in adults with MDD as a primary diagnosis.[27] The findings of the present studies are in concurrence with the available literature. Other authors have also quoted IPT and cognitive therapy (CT) to be empirically validated and commonly practiced psychological interventions for patients diagnosed as having MDD with initial response rates of up to 60%; IPT and CT are efficacious in the treatment of the disorder. A meta-analysis was conducted to evaluate IPT for depression.[28] Thirteen studies found significant and large effect sizes for IPT compared with placebo or no treatment, and superior effects of IPT compared with CBT.[29] The findings of the present study are in concurrence with the available literature. The present study also found IPT to be better than CBT.

In a large meta-analysis of studies comparing combination treatments with psychotherapy and pharmacotherapy and pharmacotherapy alone.[28] It was noted that combination treatments were significantly better than pharmacotherapy alone.[30] It is also recommended that maintenance sessions should be given for relapse prevention. Few studies have highlighted the effects of maintenance IPT along with pharmacotherapy. Maintenance IPT combined with pharmacotherapy reduced the rate of relapse as compared to IPT alone.[29]

IPT and CBT are both evidence-based treatments for MDD. IPT was noted to be as efficacious as CBT in a sample of depressed psychiatric patients in a community-based outpatient clinic. However, CBT had significantly more dropouts than IPT, indicating that CBT may be experienced as too demanding.[31] In the present study also, dropout was noted in CBT. It can be qualified by the demanding format of CBT. The present study was an attempt to evaluate the outcome of a randomized trial. The assimilation of findings suggested that IPT has emerged as an important therapy for depression with an evidence-based outcome.

Limitations

The study was conducted at a single center. The sample size was small. No follow-up assessment could be carried out.

CONCLUSION

Both CBT and IPT resulted in significant improvement in patients with depression. However, IPT has shown significantly better outcomes in comparison with CBT in the treatment of depression.

Financial support and sponsorship

AFMRC Project 4153/2017

Conflicts of interest

There are no conflicts of interest.