The Efficacy and Durability of Mindfulness-Based Cognitive Therapy in the Treatment of Anxiety and Depressive Disorders: A Systematic Review and Meta-analysis

Abstract

Purpose of the Review:

There is a dearth of meta-analytical studies measuring the durability of mindfulness-based cognitive therapy (MBCT) in the treatment of anxiety and depressive disorders. Therefore, the present study was conducted to evaluate both the effectiveness and durability of MBCT in the treatment of depression and anxiety disorders.

Collection and Analysis of Data:

We systematically searched six databases from June 11, 2023 to September 16, 2023 for randomized control trials (RCTs) of adults diagnosed with anxiety or depressive disorders as per the Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition, Text Revision or the Tenth Revision of the International Classification of Diseases and Related Health Problems diagnostic criteria; the treatment group received the complete form of MBCT, whereas the control group received other interventions or treatment as usual; the treatment outcome focused on symptoms of depression or anxiety. Two independent reviewers included studies, assessed quality, and extracted data. The Cochrane Risk-of-Bias 2.0 tool was applied to appraise the methodological quality of the included studies. R 4.2.1 software and the “metafor” package were used to estimate the effect sizes based on mean and standard deviation of anxiety and depressive disorders at baseline and postintervention, and at postintervention and follow-up periods for both the treatment and control groups.

A total of 1,470 studies were reviewed, and 21 RCTs met the inclusion criteria. The meta-analysis showed an overall standardized mean difference of −0.4806 [CI: −0.7185; −0.2428] and −0.3817 [CI: −0.5407; −0.2228] for reducing anxiety and depression symptoms, respectively indicating the effectiveness of MBCT. Comparison between postintervention and follow-up or follow-up measurement showed a small and nonsignificant effect size for depression (0.0130 [CI: −0.2109; 0.2369]) and anxiety (0.0198 [CI: −0.0660; 0.1057]), suggesting that recovered symptoms in the treatment group were maintained until the follow-up evaluation.

Conclusion:

MBCT produces long-term treatment effects in the management of both depressive and anxiety disorders.

Protocol preregistration:

The current meta-analysis followed Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines and got registered with PROSPERO (CRD42023465494).

Depression and anxiety disorders are the common mental disorders (CMDs) affecting around 322 million people worldwide or 4.4% of the global population; CMDs are more common in females (5.1%) than males (3.6%). ¹ The prevalence of CMDs in India is about 5.1%, nearly 70 million adults are suffering from CMDs, and urban residents and older adults are more vulnerable to CMDs. ² In primary care, 25% of patients are diagnosed with primary mental disorders, also having comorbid depression and anxiety disorders. ³ Additionally, approximately 90% of patients diagnosed with anxiety disorders have also been diagnosed with comorbid depressive disorders. Conversely, 85% of patients with depression also have significant anxiety-related conditions. ⁴

Mindfulness-based cognitive therapy (MBCT) is drawn primarily from cognitive behavioral therapy (CBT), mindfulness-based stress reduction, and interacting cognitive subsystems. ⁵ This evidence-based therapeutic approach was designed by Segal et al. ⁶ primarily to treat depressive disorder. MBCT helps patients by radically shifting from their thoughts, feelings, and body sensations that contribute to depressive relapses. ⁶ MBCT is effective in reducing anxiety symptoms ⁷ and the risk of depression relapse compared with treatment with antidepressants alone. ⁸ MBCT is also recommended to treat people with chronic physical health problems having comorbid depressive disorder. ⁹

Recently, many randomized control trials (RCTs) have demonstrated the effectiveness of MBCT in the treatment of stress, depression, and anxiety,^10–12 recurrence of depressive episodes,^8,13 depression and anxiety in women with premenstrual syndrome, ¹⁴ and anxiety and depression in breast cancer patients. ¹⁵

Further, systematic reviews and meta-analytic studies have been conducted to demonstrate the effectiveness of MBCT. It is reported to be effective in reducing the symptoms of patients with major depressive disorder with suicidal ideation, ¹⁶ social anxiety disorder,^17,18 generalized anxiety disorder, ¹⁹ depression and anxiety, ²⁰ recurrent major depressive disorder, ²¹ and psychological well-being. ²⁰ In another meta-analysis review, Li et al. ²² compared the effectiveness of mindfulness-based interventions and CBT in treating anxiety, depression, and sleep quality. They reported similar treatment effectiveness for both treatment methods. However, including a small number of studies was a significant limitation of many meta-analytical findings,^16,17,19,21 which further limits the generalizability of the findings.

Further, in a systematic review, Thomas et al. ²³ restricted to include the elderly participants only to measure the effectiveness of MBCT in the treatment of anxiety and depressive disorders. Most meta-analytical studies have reported the effectiveness of MBCT based on pre- and post-therapeutic observations and assessments, only another major limitation of these meta-analytical studies. Therefore, based on these findings, the temporal longevity of the effectiveness of MBCT cannot be ensured. Only Liu et al. ¹⁸ have reported the durability of MBCT in the management of social anxiety disorder with a limited number of studies.

Henceforth, this systematic review and meta-analysis aim to assess the effectiveness of MBCT in managing anxiety and depression and provide an update on the current knowledge.

Method

Protocol Preregistration

This study was registered with PROSPERO under the registration number CRD42023465494 and was carried out following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines.

Data Sources and Search Strategy

We searched PubMed, Web of Science, EBSCOhost, Ovid, Scopus, and JSTOR for relevant research papers until September 16, 2023. The search terms used were “mindfulness-based cognitive therapy” or “MBCT” and “depression or depressive disorder” or “depressive and anxiety” or “anxiety disorder” or “anxiety and depression” and “randomized-controlled trial or random* or RCT.” The articles were limited to being searched in English and published in peer-reviewed journals. Duplication of the articles was detected using HubMeta (https://hubmeta.com), and subsequently, the authors screened all titles and abstracts of the records on the basis of preset inclusion and exclusion criteria. Only RCTs that examined MBCT in the treatment of depressive disorders or anxiety disorders were included in the analysis. In the case of any discrepancy regarding the inclusion or exclusion of any article, the authors rechecked the paper and reached a consensus with discussion and deliberation. Further, the entire article was reviewed to establish the final eligibility of the article for its potential inclusion in the present meta-analysis. Finally, the following data were extracted from the included articles: (a) study characteristics (e.g., authors and year), (b) demographic characteristics (e.g., mean age and sample size), (c) treatment characteristics (e.g., type of therapy, number of sessions, and delivery format), (d) comparator characteristics (e.g., type of control group [CG]), and (e) outcome characteristics (e.g., instruments used, means, and standard deviations).

Eligibility Criteria

Inclusion Criteria

Only RCT-based articles were included where an intervention group and a CG or waitlist (WL) or treatment as usual (TAU) or control trials were designated to investigate the efficacy of MBCT involving participants who were diagnosed with either depression or anxiety disorders or both as per diagnostic criteria of Diagnostic and Statistical Manual of Mental Disorders-IV Text Revision (DSM-IV-TR) and DSM5/International Classification of Diseases (ICD) 10 or 11. The articles comprised participants of both genders between the ages of 18 and 65 years. The group-based MBCT must be delivered in face-to-face mode following the guidelines provided by Segal et al., ⁶ which were included in the present study. Regarding comparators, inactive control, WL, TAU, etc. were included. Articles published in the English language were only included.

Exclusion Criteria

We excluded the study from non-RCTs, such as controlled clinical trials, quasi-experimental designs, and case studies. We also excluded those studies in which MBCT was used in patients with bipolar disorder, brain injury, schizophrenia, schizoaffective disorder, organic mental disorder, or neurocognitive disorder (e.g., dementia, delirium, Alzheimer’s disease, etc.), as well as in patients with any form of cancer. The studies of internet-based or video-based MBCT were excluded from the present meta-analysis.

Quality Assessment

The risk of bias (RoB) within the RCTs was assessed using the Cochrane Risk-of-Bias 2.0 tool for randomized trials (RoB2, 2019 Version). The following five domains for randomized trials were assessed: (a) bias arising from the randomization process, (b) bias owing to deviations from intended interventions, (c) bias caused by missing outcome data, (d) bias in the measurement of the outcome, and (e) bias in the selection of the reported result. The Cochrane RoB tool is used to evaluate random sequence generation, allocation concealment, blinding of participants and personnel, blinding of outcome assessment, completeness of outcome data, selective reporting, and other sources of bias (Figure 2).

Figure 2. Risk of Bias (RoB2.0) Summary for the Included Studies in the Meta-analysis.

Data Extraction

Table 1 reports the procedure used for data extraction. The researchers developed a data extraction sheet to extract feature characteristics from the included studies, such as research characteristics (i.e., the authors, the publication year, the country in which the study was conducted, sample demographics, depression and anxiety measurements, and design), therapeutic characteristics (i.e., duration of therapy, number of sessions, short-term and follow-up results of mean, and SD), and group characteristics (i.e., intervention and comparison condition). The first author extracted the required details from the selected study, and the second author cross checked the accuracy of all the extracted information and all the entries.

Table 1.

Characteristics of Included Studies.

Authors and Year	Country	Design	Duration of Therapy	Number of Sessions	Follow-up Duration	Treatment Group	Control Group	Data Collected Outcome Measures
McManus et al. 27	UK	RCT	8 weeks	8 sessions	12 months	MBCT	TAU	BDI, BAI, SHAI
Chan et al. 28	China	RCT	8 weeks	8 sessions	08 weeks	MBCT	WL	DASS-21
Maddock et al. 29	Ireland	RCT	8 weeks	8 sessions	03 months	MBCT	TAU	HADS-D, HADS-A
Omidi et al. 30	Iran	RCT	8 weeks	8 sessions	NF	MBCT	TAU	BSI
Ninomiya et al. 31	Japan	RCT	8 weeks	8 sessions	NF	MBCT	WL	CESDS, STAI
Jiang et al. 24	China	RCT	8 weeks	8 sessions	03 months	MBCT	CBT	HAMD, STAI
Cladder‑Micus et al. 32	Netherland	RCT	8 weeks	8 sessions	NF	MBCT	TAU	IDS-SR; VASMA
Geschwind et al. 33	UK	RCT	8 weeks	8 sessions	06 months	MBCT	WL	HAMD, IDS-SR
Musa et al. 34	Nigeria	RCT	8 weeks	8 sessions	02 months	MBCT	CG	BDI-II
Tovote et al. 25	Netherland	RCT	8 weeks	8 sessions	NF	MBCT	CBT	BDI-II, GAD-7
Spinhoven et al. 26	Netherland	RCT	8 weeks	8 sessions	06 months	MBCT	CBT	BAI
Cladder‑Micus et al. 35	Netherland	RCT	8 weeks	8 sessions	NF	MBCT	TAU	IDS-SR
Shih et al. 36	China	RCT	8 weeks	8 sessions	NF	MBCT	AC	HADS
van Son et al. 37	Netherland	RCT	8 weeks	8 sessions	06 months	MBCT	TAU	POMS, HADS
Assumpcao et al. 38	Brazil	RCT	8 weeks	8 sessions	03 months	MBCT	WL	BDI-II, BAI
Chiesa at al. 39	Italy	RCT	8 weeks	8 sessions	NF	MBCT	Psycho-education	HAMD
Manicavasgar et al. 40	Australia	RTC	8 weeks	8 sessions	12 months	MBCT	CBT	BDI-II, BAI
Shallcross et al. 41	USA	RCT	8 weeks	8 sessions	60 weeks	MBCT	AC	BDI-II
Schanche et al. 42	Norway	RCT	8 weeks	8 sessions	NF	MBCT	WL	BDI-II, BAI
Pots et al. 43	USA	RCT	8 weeks	8 sessions	6 months	MBCT	Wait-List	CESDS, HADS-A
van Aalderen et al. 44	Netherlands	RTC	8 weeks	8 sessions	NF	MBCT	TAU	BDI, HAMD

RCT: Randomized Controlled Trail; MBCT: Mindfulness-based Cognitive Therapy, CBT: Cognitive Behavioral Therapy; AC: Active Control; ACG: Active Control Group; CG: Control Group; TAU: Treatment As Usual; WL: Waitlist; NF: No Follow-up; BDI: Beck Depression Inventory; BAI: Beck Anxiety Inventory; SHAI: Short Health Anxiety Inventory; DASS-21: Depression Anxiety and Stress Scale-21; HADS-D Hospital Anxiety and Depression Scale-Depression; HADS-A Hospital Anxiety and Depression Scale-Anxiety Scale; BSI: Brief Symptom Inventory; CESDS: Center for Epidemiologic Studies Depression Scale; STAI: State-Trait Anxiety Inventory; HAMD: Hamilton Depression Scale; VASMA: Visual Analog Scale for Measuring Anxiety; GAD-7: Generalized Anxiety Disorder 7 Items; POMS: The Profile of Mood States; IDS-SR: The Inventory of Depressive Symptomatology Self-Report; IDS-SR: Inventory of Depressive Symptomatology Self-Report.

Results

Study Selection

The original search results in 2044 studies were found through an electronic search of 6 databases, and 569 duplicate studies were removed. After carefully examining titles and abstracts, 1324 studies that did not meet the inclusion criteria were excluded. In the first phase of the eligibility screening, 146 studies were screened according to the inclusion and exclusion criteria. After a full-text review, 125 studies were excluded, and 21 were found eligible. In the final phase, 21 studies were included in the review process. The selection process is shown in the flow diagram in Figure 1.

Figure 1. PRISMA Flowchart (2020) of the Inclusion Process of Studies.

Characteristics of the Studies

The characteristics of the 21 included studies that published between 2003 and 2023 are summarized in Table 1. The studies were published in various countries. The types of CGs include TAU, WL, CBT, and other interventions. Seven studies compared MBCT with TAU, six studies compared MBCT with a WL, four studies compared MBCT with CBT, two studies compared MBCT with an active control group (ACG), one study compared MBCT with the CG, and one study compared MBCT with psychoeducation (see Table 1).

Risk of Bias of the Studies

Figure 2 demonstrates the RoB for the included RCTs. Most studies (i.e., 19 studies) included in the present meta-analysis were rated as having a low RoBs across most domains, suggesting robust study designs were implemented in the included studies. However, three studies^24–26 were rated as raising concerns in some domains. Therefore, most studies demonstrated a low RoB, as shown in Figure 2.

Intervention Characteristics and Outcome Measures

Treatments implemented in various types of research exhibit similarities in the structure of MBCT. In all the studies in the present meta-analysis, the standard MBCT was implemented with weekly sessions over eight weeks, each lasting 2 to 2.5 hours. The CGs comprised WL, TAU, and ACG. The most common measures for depression and anxiety were the Beck Depression Inventory (BDI), Beck Anxiety Inventory (BAI), Depression, Anxiety and Stress Scale (DASS-21), and Hamilton Depression Scale (HAMD) (see Table 1).

Meta-analysis

The meta-analysis was conducted through the R 4.2.1 software using “meta,” ⁴⁵ “metafor,” ⁴⁶ and “dmetar” ⁴⁷ packages. All statistical tests were conducted at a significance level of 5% (two-tailed tests). In particular, using the “metafor” package, all the studies’ effect sizes and standard errors were calculated using the cmicalc() function. Further, the metagen() function was used to synthesize estimated effect sizes and standard errors. All the studies are based on pre-test, post-test, and CG design, and most of the studies provided mean and standard deviations of both pre-, post-, and follow-up assessment measures of treatment group (TG) and CG. The effect size and standard errors for both baseline and post-therapeutic comparisons and post- and follow-up therapeutic comparisons for anxiety and depressive symptoms were computed using the convention provided by Morris et al. ⁴⁸ . In some studies, wherein the effect size and 95% CI of the effect size were reported, the standard errors of studies were estimated accordingly. The forest plot was created using the forest() function. To measure the presence of possible publication bias in the present meta-analysis, the funnel() function was used. Finally, a sensitivity analysis was performed to remove influential and outlier studies that could bias the effect size estimate and precision. ⁴⁷ To perform a sensitivity analysis, the functions “find.outliers()” and “InfluenceAnalysis()” of the package were used. ⁴⁷

Efficacy of MBCT in the Treatment of Depression and Anxiety

The meta-analysis included 19 studies (K) in which MBCT was used as a treatment method to treat depressive symptoms (Figure 3). A comparison of depressive symptoms between pretreatment and post-treatment conditions suggests that MBCT is effective in reducing depressive symptoms compared to TAU (SMD = −0.4806, t = −4.25, p < .001). The results of heterogeneity analysis (Q/χ² = 1534.24, df = 18, p < .001) and I² = 98.8% suggest the presence of significant heterogeneity across the findings reporting the effectiveness of MBCT in the treatment of depression (Table 2).

Figure 3. Forest Plot Representing Comparison of Pre-intervention and Post-intervention Depression Scores of MBCT vs Tau.

Table 2.

Pooled Effect Sizes for MBCT and Control Conditions for the Management Depression and Anxiety.

Condition/Functioning Index	Studies	Heterogeneity						Effect Size
	K	Q	H	I2	tau^2	df	p Value	SMD	95% CI	t Value	p Value
Pre- and Post-comparisons
• Depression • Anxiety	19 14	1534.24 212.34	9.23 4.04	98.8% 93.9%	0.2333 0.0676	18 13	<.001 <.001	–0.4806 –0.3817	[–0.7185; –0.2428] [–0.5407; –0.2228]	–4.25 –5.19	<.001 <.001
Post-follow-up comparisons
• Depression • Anxiety	10 09	576.75 90.44	8.01 3.36	98.4% 91.2%	0.0958 0.0111	9 8	<.001 <.001	0.0130 0.0198	[–0.2109; 0.2369] [–0.0660; 0.1057]	0.13 0.53	.898 .608

K: The number of studies; Q: Cochrane Q test for Heterogeneity; df: Degree of freedom; SMD: Standardized mean difference; CI: Confidence interval.

A total of 14 studies used in the present meta-analysis demonstrate the effectiveness of MBCT in treating anxiety disorders (Figure 4, Table 2). Results of comparisons between pre-therapeutic and post-therapeutic conditions of anxiety-related symptoms show that MBCT contributes to a significant symptom reduction in the TG compared to TAUs (SMD = −0.3817, t = −5.19, p < .001). Furthermore, heterogeneity has been observed among the findings of different studies assessing the effectiveness of MBCT in treating anxiety disorders (Q/χ² = 212.34, df = 13, p < .001).

Figure 4. Forest Plot Representing Comparison of Pre-intervention and Post-intervention Anxiety Scores of MBCT vs Tau.

Durability of MBCT in the Treatment of Depression and Anxiety Disorders

A total of 10 studies compared the level of depression between the TG and the CG in the post-therapeutic phase and in the follow-up phase (Table 2, Figure 5). Findings suggest that improved depressive symptoms through MBCT are maintained until follow-up assessment (SMD = 0.0130, t = 0.13, p = .8980). Since the pooled SMD between both groups is not significant, this indicates that the symptoms reduced in the post-therapeutic period persisted until the follow-up period in the TG. The level of depression measured in the CG during the post-assessment phase remained the same compared to the assessment done in the follow-up phase (Figure 5). Heterogeneity has been observed across the studies reporting the durability of MBCT in managing depression (Q/χ² = 576.75, df = 9, p < .001).

Figure 5. Forest Plot Representing Comparison of Post-intervention and Follow-Up Depression Scores of MBCT.

Similarly, only nine studies compared the level of anxiety between the TG and the CG in the post-therapeutic and follow-up phases of the studies (Table 2, Figure 6). Findings based on nine studies suggest that reduced levels of symptoms of anxiety in the post-therapeutic assessment were maintained to a similar degree till the follow-up assessment, and in the CG, the level of anxiety assessed in the post-assessment phase remained the same compared to the assessment done in the follow-up phase (Figure 6). It can be further inferred from the findings that improved anxiety symptoms through MBCT were maintained till the follow-up assessment (SMD = −0.0660, t = 0.53, p = .60). Further, a significant number of heterogeneities were observed across the findings reporting the durability of MBCT in the treatment of anxiety disorders (Q/χ² = 90.44, df = 8, p < .001).

Figure 6. Forest Plot Representing Comparison of Post-intervention and Follow-Up Anxiety Scores of MBCT.

A series of Egger’s regression tests ⁴⁹ were performed to estimate the possible presence of publication bias for the studies representing the efficacy of MBCT in the management of depression and anxiety disorders. The obtained intercept (β₀) values were 5.5296 (t = −0.08, df = 17, p = .93) and 2.6380 (t = 0.23, df = 12, p = .81) for both depression and anxiety-related studies, respectively, significantly greater than zero, which further indicates the absence of publication bias in the present meta-analysis measuring the efficacy of MBCT in the management of depression and anxiety disorders.

The “InfluenceAnalysis()” function is used to conduct influence diagnostics by leave-one-out meta-analysis results for the pre-therapeutic and post-therapeutic comparisons for both anxiety and depressive disorders sorted by their effect size ⁴⁷ . Further, the Baujat plot ⁵⁰ detects studies that overly contribute to heterogeneity in a meta-analysis. It is evident from the leave-one-out meta-analysis (Figures S1 and S2) sorted based on effect size and stability among the findings of the present meta-analysis, both for anxiety and depressive disorders. However, per the leave-one-out meta-analysis sorted based on effect size (Figures S1 and S2) and Baujat plots (Figures S3 and S4), five and three possible influential studies were detected for depressive and anxiety disorders, respectively. Further, outlier analysis using the “find.outliers()” function also revealed the presence of nine and four possible outlier studies, respectively, both for depression and anxiety disorders. Even after removing nine outlier studies and five influential studies for depressive disorders and removing four outlier studies and three influential studies for anxiety disorders, MBCT was found effective in the management of both anxiety and depressive disorders ( Tables 3 and 4 ). Both outlier analysis and influential analysis indicate that stability is present regarding the efficacy of MBCT in the management of depression and anxiety disorders.

Table 3.

Sensitivity Analysis for Depressive Disorders.

Analysis	SMD for Pre- and Post-Therapeutic Comparison	95% CI	I2	Q	t	Number of Studies	P Value
Influential Studies Removed1	–0.4795	[0.0502; 0.3196]	96.1%	331.85	–5.30	14	<.001
Outlier Studies Removed2	–0.4003	[–0.5111; –0.2895]	93.2%	131.73	–8.17	10	<.001

¹Influential studies removed: Shallcross et al. (2015), Assumpcao et al. (2023), Geschwind et al. (2012), Tovote et al. (2014), Omidi et al. (2013).

²Outliers removed: Omidi et al. (2013), Geschwind et al. (2012), Musa et al. (2020), Tovote et al. (2014), Shih et al. (2021), Assumpcao et al. (2023), Chiesa at al. (2012), Manicavasgar et al. (2010), Shallcross et al. (2015).

Table 4.

Sensitivity Analysis for Anxiety Disorders.

Analysis	SMD for Pre- and Post-Therapeutic Comparison	95% CI	I2	Q	t	Number of Studies	P value
Influential Studies Removed1	–0.3538	[–0.4842; –0.2234]	85.4%	68.59	–6.05	11	<.001
Outlier Studies Removed2	–0.3082	[–0.3785; –0.2380]	78.6%	42.10	–9.92	10	<.001

¹Influential studies removed: Omidi et al. (2013), van Son et al. (2014), Manicavasgar et al. (2010).

²Outliers removed: Omidi et al. (2013), Ninomiya et al. (2020), van Son et al. (2014), Manicavasgar et al. (2010).

Discussions

The findings of the present study indicate that eight weeks of MBCT significantly reduced symptoms of both anxiety and depression, and reduced anxiety and depressive symptoms were maintained until follow-up. The present findings are aligned with previously reported meta-analytical findings that have also reported that MBCT is effective in the management of various anxiety and depression-related clinical conditions, such as social anxiety disorder,^17,18 generalized anxiety disorder, ¹⁹ and depression and anxiety, ²⁰ and recurrent major depressive disorder. ²¹ In a network meta-analysis-based study, McCartney et al. ⁵¹ also found the effectiveness of MBCT as a preventative treatment in the management of recurrent depression.

The findings of the present study suggest that MBCT produces long-term treatment effects in the management of both anxiety and depressive disorders. The present findings are similar to the meta-analytical findings of Liu et al. ¹⁸ , who have reported the long-term effectiveness of MBCT in the management of social anxiety disorder. However, there is a scarcity of literature to measure long-term efficacy in the management of the symptoms of anxiety and depression. Similarly, in a network meta-analytical-based study, McCartney et al. ⁵¹ reported the long-term treatment effectiveness of MBCT in preventing depression replacement.

The results also suggest significant heterogeneity present across the findings evaluating the effectiveness of MBCT in the management of anxiety and depressive disorders. Heterogeneity can be preceded by differences in diagnostic tools, diagnostic criteria, the setting, severity of the patients, etc, in the conducted RCTs. Also, there is an absence of publication bias in the present meta-analysis, as the present meta-analysis is based on 21 RCTs.

Findings of sensitivity analysis, such as influential and outlier analysis, suggest that stability is present across the findings evaluating the effectiveness of MBCT. We have removed both types of studies that have highly contributing effect sizes and a high degree of variability. Even after removing both types of studies, MBCT was found effective in the management of depression and anxiety disorders. We did not perform sensitivity analysis for studies measuring the long-term effectiveness or durability of MBCT, as a smaller number of studies reported both depression and anxiety.

The present meta-analysis is one of the first attempts to analyze both the efficacy and durability of MBCT in the treatment of anxiety and depressive disorders. Despite its strength being the inclusion of a wide range of RCTs and interventions from six online databases, the study also has certain limitations. For instance, in almost all RCTs, patients received antidepressant and anxiolytic medications in addition to receiving MBCT. Almost all studies did not describe the type and dosage of medications used to treat patients along with MBCT. Therefore, there is a possible moderating effect of the type and dosage of both anxiolytic and antidepressant medications on the recovery process of patients that we did not control in the present study. Although we assumed that the same medical team would treat both TG and CG participants owing to randomization, there are similarities in the conditions of pharmacological treatment within the study.

Modality and the number of sessions of MBCT could also be possible sources of biases and errors while computing pooled SMD of all studies. To control this bias, we only included those studies that implemented MBCT in eight sessions within eight weeks. Additionally, all the sessions were implemented through face-to-face mode only. Although MBCTs implemented through internet-based or video-based studies were excluded from the present meta-analysis, it could be a possible source of publication bias. As the number of studies in the present meta-analysis is limited, we could not estimate the efficacy of the MBCT disorder subtypes.

Conclusion

The present study was one of the first attempts to evaluate the effectiveness and durability of MBCT and found that it is practical and durable in treating anxiety and depressive disorders. Therefore, this therapeutic procedure is recommended as an adjunct to conventional pharmacotherapy to treat both disorders. The findings on the long-term effectiveness of MBCT are still preliminary, as they are based on limited studies.