Depresyonda Göz Hareketleriyle Duyarsızlaştırma ve Yeniden İşleme Tedavisinin Etkinliği: Randomize Kontrollü Çalışmaların Meta Analizi ve Meta-Regresyonu (The Efficacy of Eye Movement Desensitization and Reprocessing Treatment for Depression: A Meta-Analysis and Meta-Regression of Randomized Controlled Trials)

The Efficacy of Eye Movement Desensitization and Reprocessing Treatment for Depression: A Meta-Analysis and Meta-Regression of Randomized Controlled Trials

 

Depresyonda Göz Hareketleriyle Duyarsızlaştırma ve Yeniden İşleme Tedavisinin Etkinliği: Randomize Kontrollü Çalışmaların Meta Analizi ve Meta-Regresyonu (The Efficacy of Eye Movement Desensitization and Reprocessing Treatment for Depression: A Meta-Analysis and Meta-Regression of Randomized Controlled Trials)

23.9.24

 

Ji-Woo Seok and Joong Il Kim

 

Digital Health Research Division, Korea Institute of Oriental Medicine, Daejeon 34054, Republic of Korea; suk6124@kiom.re.kr

* Correspondence: jikim@kiom.re.kr; Tel.: +82-042-868-9525; Fax: +82-042-861-5800

 

Translated by: Specialist Psychologist Gizem Pozam

 

Abstract
Background: Eye Movement Desensitization and Reprocessing (EMDR) therapy has attracted attention for its potential efficacy in treating depression beyond its initial use for PTSD. This systematic review and meta-analysis aims to evaluate the efficacy of EMDR in treating depression and identify variables that influence its efficacy.

 

Methods: A comprehensive search was conducted in databases including MEDLINE, PubMed, and EMBASE, covering studies through January 2023. A total of 521 studies were screened, and 25 studies involving 1042 participants (522 EMDR, 520 controls) met the inclusion criteria and were included in the meta-analysis. Inclusion criteria comprised randomized controlled trials (RCTs) comparing EMDR with control conditions such as usual care or waiting-list groups, with outcomes focusing on changes in depressive symptoms.

 

Results: The results indicate that EMDR has a significant effect on reducing depressive symptoms (Hedges' g = 0.75), with moderate heterogeneity observed. Meta-regression showed that depression severity was a significant predictor of EMDR efficacy, with larger effects in severe cases. In addition, the systematic review analyzed and evaluated various theoretical models and related studies explaining how EMDR works in treating depression and reported neurobiological models proposed in previous research.

Conclusion This study confirms that EMDR is effective in treating depression, particularly in severe cases, and highlights its potential as a nonpharmacological intervention. However, this study emphasizes the need for more standardized research and long-term assessments to evaluate the lasting effects of EMDR. Integrating EMDR into multimodal treatment plans and first-line treatment, particularly for treatment-resistant depression, could significantly improve patient outcomes.

 

 

Keywords: Eye Movement Desensitization and Reprocessing; depression; meta-analysis; meta-regression; psychotherapy; efficacy

 

1. Background

 

Depression is a major global mental health problem with a steadily increasing prevalence. Depression remains a growing concern, with psychological distress significantly exacerbated by the COVID-19 pandemic. Depression rates have increased across OECD countries, while the prevalence of depressive symptoms has remained above pre-pandemic levels. Although some countries, such as Korea, the United Kingdom, and the United States, showed slight improvements in 2022, prevalence remained at least 20% higher than pre-pandemic levels . The OECD report also points to higher rates of depression among women and older adults, further exacerbating existing mental health inequalities .

 

Depression significantly impairs individuals' quality of life and functioning, and the World Health Organization has identified it as a leading cause of premature death and disability [2,3]. The worldwide socioeconomic cost of depression is enormous, with estimates exceeding USD 1 trillion annually [4,5]. This figure underscores the critical importance of preventing and treating depression, not only to improve individual well-being but also to reduce substantial societal and economic burdens [4,6]. Addressing depression through effective prevention and treatment strategies is essential to reducing these costs and improving overall public health outcomes .

 

Treatment for depression has advanced significantly in recent years with the development of various options, including pharmacotherapy, psychotherapy, and combinations of the two . Although pharmacotherapy is effective in alleviating depressive symptoms, approximately 20–30% of all patients with depression are reported not to respond to medication . In addition, despite cognitive behavioral therapy doubling the response rate, the relapse rate for depression remains as high as 25% after two years [9,10]. Given these limitations, there is growing demand for alternative treatment approaches, particularly for those experiencing treatment-resistant depression. In this context, EMDR has emerged as a promising nonpharmacological intervention for depression. Originally developed for PTSD, EMDR has demonstrated significant efficacy in alleviating depressive symptoms, particularly in severe cases. Furthermore, the COVID-19 pandemic highlighted the adaptability of EMDR, as the transition to online therapy demonstrated its flexibility in providing continuity of care when traditional face-to-face therapies were disrupted .

 

Previous studies have shown that depression can be triggered and maintained by stressful life events and traumatic experiences [12,13]. Recent studies have reported that traumatic events, such as physical and emotional abuse, not only serve as significant psychosocial risk factors for major depressive disorder (MDD) but also contribute to relapse, persistence, and treatment resistance in depression . Consequently, it has been hypothesized that Eye Movement Desensitization and Reprocessing (EMDR), a successful treatment for trauma, may also be effective in treating depression .

 

EMDR is a psychological intervention technique developed by Francine Shapiro in 1989 and used primarily to treat symptoms associated with traumatic memories [16,17]. This intervention aims to reprocess and integrate traumatic memories through eye movements, thereby reducing the negative emotions and somatic symptoms triggered by these memories. It involves an eight-phase protocol consisting of (1) history-taking and treatment planning, (2) preparation, (3) assessment of the traumatic memory, (4) desensitization, (5) installation of a positive belief, (6) body scan, (7) closure, and (8) reevaluation [18,19].

 

Research shows that EMDR engages fundamental cognitive processes such as attention, memory, and associative learning, all of which are critical to understanding and treating depression [20,21]. By guiding patients through bilateral stimulation and memory reprocessing, EMDR helps shift attentional focus away from negative, trauma-related information, improving emotional regulation and cognitive flexibility . EMDR may also affect working memory by overloading cognitive resources, reducing the vividness and emotional intensity of distressing memories . This process facilitates associative learning, enabling patients to form new, adaptive connections between past experiences and present emotions, which is crucial for restructuring the maladaptive thoughts commonly found in depressive episodes [21,23]. Given that depression often involves dysfunctional cognitive patterns such as rumination, memory biases, and impaired associative learning, the cognitive mechanisms engaged during EMDR play a key role in reducing depressive symptoms [23,24]. Understanding how EMDR interacts with these cognitive processes offers deeper insight into its potential to treat depression, making a valuable contribution to the growing body of evidence supporting its broader therapeutic application.

 

Previous studies of EMDR therapy have reported that it may be effective in treating symptoms associated with major depression [25,26]. Ostacoli et al. (2018) conducted a study comparing EMDR and cognitive behavioral therapy (CBT) as adjunctive treatments to antidepressants in patients with recurrent depression. The results indicate that EMDR reduced depressive symptoms to the same extent as CBT, both at the end of treatment and six months later . Another study compared EMDR with trauma-focused CBT in patients with treatment-resistant depression and found that both treatments reduced depressive symptoms, but EMDR had a greater effect, and only patients receiving EMDR maintained sustained improvement at follow-up assessments . A systematic review of studies using EMDR to treat PTSD and pain reported that EMDR could significantly reduce not only PTSD symptoms but also accompanying depressive symptoms [15,29].

 

Recently, a depression-specific EMDR treatment protocol known as DeprEND® was introduced [18,30,31]. This protocol focuses on changing negative belief patterns and self-blame associated with depression. Previous studies have reported that DeprEND® reduces PTSD-related depressive symptoms more effectively than CBT [32,33]. Despite the positive findings reported in EMDR studies to date, the generalizability of these results is limited by heterogeneity in study designs and variability in the assessment methods used.

 

A recent review of the efficacy of EMDR therapy for major depression suggested that EMDR may be potentially effective in treating depression; however, it also highlighted methodological problems in the included studies [32,34]. Specifically, the review identified shortcomings such as a lack of randomization, small sample sizes, and reliance on self-report measures, which may lead to overestimation of the intervention's efficacy. The authors concluded that further research was needed to strengthen the evidence base .

 

Therefore, this study aims to update the evidence on EMDR efficacy by conducting a systematic review that includes recent randomized controlled trials (RCTs). A meta-analysis will also be conducted to provide a quantitative evaluation of EMDR efficacy in treating depression, thereby enabling more definitive conclusions. To further reduce heterogeneity between studies arising from methodological differences, a meta-regression analysis will be performed to investigate specific variables that may systematically contribute to heterogeneity. By adjusting for the effects of these variables, this study aims to provide more reliable and valid evidence on EMDR efficacy.

 

1. Methods

2.1. Study Design

 

This study includes a meta-analysis and meta-regression analysis conducted to evaluate the efficacy of EMDR in treating depression.

 

2.2. Selection and Exclusion Criteria

 

This study was registered with PROSPERO for transparency (Registration Number: CRD420234 01981) and conducted in accordance with the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. Two reviewers independently screened the retrieved studies against predefined selection criteria. The inclusion criteria for the meta-analysis were as follows: (1) Population: individuals diagnosed with depression according to depression assessment instruments; (2) Intervention: EMDR therapy; (3) Comparison: control groups receiving no intervention (e.g., no treatment, waiting-list control, placebo, or usual care); (4) Outcomes: changes in depressive symptoms; and (5) Study Design: randomized controlled trials and observational studies. The exclusion criteria were as follows: (1) studies involving patients already receiving medication, (2) studies involving psychological therapies other than EMDR as part of the intervention, (3) studies not reporting depression outcomes, and (4) literature reviews, case reports, and qualitative studies.

 

2.3. Data Search and Selection Process

 

A literature search was conducted in electronic databases, including Google Scholar, MEDLINE, PubMed, the Cochrane Central Register of Controlled Trials (CENTRAL), EMBASE, Web of Science, PsycINFO, and ProQuest Dissertations, covering the period from each database's inception through January 2023. The following key search terms were used: (depression OR depressive symptom OR Major depressive disorder) AND (EMDR OR Eye Movement Desensitization and Reprocessing OR eye movement psychotherapy) AND (randomized OR random OR randomization OR RCT OR RCTs) AND (Waiting List OR TAU OR treatment as usual OR no intervention OR CAU OR care as usual). In addition, the reference lists of identified studies and relevant articles suggested by meta-analyses and systematic reviews were manually examined. There were no restrictions on country of publication, participant sex, or race.

 

After duplicate records were removed from the literature collected through electronic databases and manual searches, titles and abstracts were reviewed to initially select relevant studies. Full texts were then reviewed against the inclusion and exclusion criteria to select the final studies. The selection process was conducted independently by two researchers. In cases of disagreement, studies were reassessed against the inclusion and exclusion criteria, exclusion criteria were established, and consensus was reached through discussion.

 

2.4. Quality Assessment of Included Studies

 

Two independent reviewers conducted a full-text review of the included studies and assessed the quality of each study included in the meta-analysis using the Cochrane Risk of Bias Tool for RCTs. The quality assessment considered the following bias categories: selection bias (random sequence generation and allocation concealment), reporting bias (selective reporting), performance bias (blinding of participants and personnel), detection bias (blinding of outcome assessment), attrition bias (incomplete outcome data), and other sources of bias. Each of these domains was rated as having low, high, or unclear risk. Quality assessment results were cross-checked, and any disagreements between reviewers were resolved through discussion to reach consensus or by consulting a third party.

 

2.5. Data Extraction and Analysis

 

A coding framework was developed based on relevant previous studies in the literature, and two research assistants extracted relevant information using this framework. The data extraction form included information on participant characteristics and intervention methods, such as title, author, year of publication, participant age, sex, sample size, participant characteristics (e.g., refugees, PTSD, or phobias), type of control condition, intervention duration, duration per session, total number of sessions, depression measurement instruments, and overall depression scores before and after the intervention. When post-intervention scores were reported at multiple follow-up points, only the assessment conducted immediately after the intervention was considered. Extracted data were cross-checked, and consensus was reached through discussion.

 

2.6. Statistical Analysis

 

Statistical analyses were performed using the “meta” package in R (version 4.4.1). The pooled effect size was calculated using a random-effects model, considering variability in sample size, intervention methods, and duration across studies . Effect size was assessed using Hedges' g, which adjusts for bias in Cohen's d, particularly when comparing mean differences between two groups . Cohen's d tends to overestimate effect sizes in small samples, making it difficult to accurately estimate the population standard deviation. Because many studies included in this meta-analysis had small sample sizes, effect sizes were corrected using Hedges' g [38,39]. An effect size is interpreted as small if less than 0.15, moderate if between 0.40 and 0.74, and large if greater than 0.75 . The effect size is interpreted with a 95% confidence interval indicating precision. If the confidence interval is greater than 0, the effect is considered significant; if it includes 0, it is not considered significant . A narrower confidence interval indicates a more precise estimated effect size, meaning the estimate is closer to the true effect .

 

In this study, heterogeneity between studies was visually assessed using a forest plot. The Q statistic and I2 index were also calculated. The Q value measures variability among effect size estimates across studies, while the I2 index expresses the proportion of total variability attributable to heterogeneity as a percentage. Generally, a Q value with a significance level of 0.1 or lower, or an I2 index of 50% or higher, indicates substantial heterogeneity between studies .

 

A meta-regression analysis was conducted to investigate the sources of heterogeneity observed in the meta-analysis and provide further explanations. This analysis assessed the moderating effects of study-level characteristics, such as depression severity, age, and the total number of EMDR sessions .

 

 

1. Results

3.1. Study Selection

The literature search identified a total of 521 studies. Of these, 508 were retrieved through database searches, and another 13 were identified through snowball sampling.

 

 

Initially, 421 duplicate studies were removed. The titles and abstracts of the remaining studies were then screened against the inclusion and exclusion criteria, resulting in 59 studies being selected for further screening. However, 12 of these studies were excluded because of inappropriate interventions, such as comparing EMDR efficacy with other interventions (e.g., CBT and exposure therapy), using combined methods involving EMDR and the emotional freedom technique, or combining EMDR with pharmacotherapy. In addition, 10 studies were excluded because they did not use a randomized experimental design, 8 because they did not provide calculable statistical results, 3 because they were quasi-experimental, and 2 because, although they provided effect sizes, it was not possible to extract means and standard deviations for each group before and after the intervention.

 

 

 

3.2. Study Characteristics

 

The characteristics of the 25 studies included in the meta-analysis are summarized (Table 1). The summary includes information on authors, year of publication, participant characteristics, age, number of participants, type of control group, intervention duration, frequency and period, total number of intervention sessions, and diagnostic assessment of depression.

 

 

The 25 studies analyzed were published between 1994 and 2023. Specifically, there were 2 studies from the 1990s, 6 published between 2000 and 2010, 13 published between 2011 and 2019, and 4 published after 2020. Participants included refugees, patients with PTSD, individuals with depression, patients with phobias, and those with bipolar disorder, all of whom met the diagnostic criteria for depression according to a diagnostic assessment. Of the 25 studies, 3 focused on children and adolescents, while the remaining studies involved adult participants. Sample sizes in individual studies ranged from a minimum of 17 to a maximum of 83 participants, with a total of 522 participants in the EMDR intervention groups and 520 in the control groups. Regarding control groups, 17 studies used no-treatment controls, 7 used usual care, and 1 evaluated both no-treatment and usual-care controls.

 

EMDR sessions ranged from 50 to 90 minutes per session. In terms of the number of intervention sessions, 1 study involved 1 intervention session, 12 involved 1–5 sessions, 9 involved 6–10 sessions, and 3 involved 12 sessions. In addition, in four studies, the number of intervention sessions was not fixed but tailored to each participant's needs, and an average number of sessions was reported.

 

The most commonly used assessment for measuring depression was the Beck Depression Inventory, used in 14 studies. Other instruments included the Hamilton Depression Rating Scale, the depression subscale of the Hospital Anxiety and Depression Scale, the Children's Depression Inventory, the Patient Health Questionnaire, the Center for Epidemiologic Studies Depression Scale, and the Self-Rating Depression Scale.

 

3.3. Quality Assessment Results

 

A risk-of-bias analysis was performed using Review Manager software version 5.4 (Nordic Cochrane Center, Copenhagen, Denmark). Table S1 provides a summary of the risk of bias for each study, showing that 36% of studies were assessed as having a low overall risk of bias. The main issues identified were the absence of intention-to-treat analyses and inadequate reporting of allocation concealment.

 

While most studies used appropriate randomization methods, one study did not implement allocation concealment, and fourteen studies mentioned it without providing specific details. Of the 25 studies, 20 reported participant dropout rates, ranging from 0% to 25%. Of the 16 studies with dropout rates greater than 0%, 11 performed an intention-to-treat analysis based on the groups to which participants were originally assigned (Table S1).

 

 

3.4. Analysis of EMDR Effect Size and Moderator Effects

 

Effect sizes (Hedges' g) for the 25 selected studies (e.g., 26 trials) were calculated and presented in a forest plot (Figure 2). The overall mean effect size was Hedges' g = 0.75 (95% CI: 0.54–0.97), indicating a large and statistically significant effect. Study heterogeneity, measured as the proportion of total variance attributable to between-study variance, was I2 = 62.80% (Q = 65.53, df = 25, and p < 0.001), indicating moderate heterogeneity.

 

To explain heterogeneity in effect sizes between studies, a meta-regression analysis was conducted using sample size, number of intervention sessions, participant age (e.g., adults versus children/adolescents), and participants' depression severity (e.g., mild and severe) as moderator variables. When sample size was used as a predictor, the estimate was -0.006 and was not statistically significant (p = 0.262). Similarly, the estimates for number of sessions and participant age were 0.030 and 0.099, respectively, and neither was statistically significant (p = 0.966 and p = 0.284). However, the estimate for participants' depression severity was 0.602 and was statistically significant (p = 0.007). This indicates that the effect size of EMDR increased as participants' depression severity increased (Table 2).

 

 

 

3.5. Subgroup Analyses

 

To inform the clinical application of EMDR, a subgroup analysis was conducted by dividing the number of EMDR sessions into three groups: 5 or fewer sessions, 6–10 sessions, and more than 11 sessions. The results of this analysis are presented in Figure 3. The mean effect size for each subgroup was statistically significant. Specifically, the effect size for 5 or fewer sessions was Hedges' g = 0.62 (95% CI: 0.42–0.82; I2 = 0%; Q = 9.78; df = 10; p = 0.46); for 6–10 sessions, Hedges' g = 0.44 (95% CI: 0.03–0.84; I2 = 62.56%; Q = 13.65; df = 5; p = 0.018); and for more than 11 sessions, Hedges' g = 1.13 (95% CI: 0.72–1.54; I2 = 66.22%; Q = 24.54; df = 8; p = 0.002). Although heterogeneity remained moderate to high, the effect size was largest for interventions involving more than 11 sessions.

 

 

 

To examine differences in EMDR efficacy according to depression severity, a subgroup analysis was conducted by categorizing depressive symptoms as mild or moderate-to-severe (Figure 4). For the group with mild depression, the effect size was Hedges' g = 0.46 (95% CI: 0.21–0.71), indicating a moderate effect size with low heterogeneity (I2 = 35.85%; Q = 20.74; df = 12; p = 0.054). In the group with moderate-to-severe depression, the effect size was Hedges' g = 0.99 (95% CI: 0.71–1.26), indicating a large effect size, while heterogeneity remained moderate to high (I2 = 57.99%; Q = 29.36; df = 12; p < 0.05).

 

 

 

3.6. Analysis of Publication Bias

 

To verify the integrity and validity of the study results, publication bias was estimated, beginning with a funnel plot analysis to examine asymmetry in effect sizes [39,68]. The funnel plot, which visualizes the studies' effect sizes and standard errors, showed that data points were mostly distributed symmetrically around the mean effect size, although a few studies were concentrated in the lower-right corner (Figure S1). This suggests that publication bias was unlikely to have a substantial effect on the overall results of the meta-analysis.

 

 

Egger's regression test was performed to objectively assess asymmetry in effect sizes. The result indicated bias = 1.536 (p = 0.124), showing that publication bias was not statistically significant.

 

Given the slight clustering observed in the lower-right corner of the funnel plot, the trim-and-fill method was applied to adjust for potential publication bias. After recalculating the adjusted effect size, it was found that including one additional study would make the funnel plot symmetrical. The corrected effect size was adjusted from 0.75 to 0.73, confirming that the detected publication bias did not substantially affect the overall study results (Figure S2).

 

1. Discussion

 

The aim of this systematic review, meta-analysis, and meta-regression is to provide an update on the latest research on EMDR interventions for depression, quantitatively analyze their efficacy, and identify specific variables influencing EMDR efficacy. The findings indicate that EMDR, primarily associated with PTSD treatment, can also be effectively applied to the treatment of mental health problems such as depression.

 

The meta-analysis results indicate that EMDR has a significant effect in treating depression, although moderate heterogeneity was observed and only eight studies were assessed as having a low risk of bias. The findings show that, at the end of the studies, EMDR therapy was more effective in treating depression than control conditions (e.g., usual care or waiting list) (Hedges' g = 0.75, adjusted to 0.73 after trim-and-fill correction). The meta-regression analysis showed that EMDR efficacy was consistent regardless of study methodology (e.g., number of sessions and sample size) or participants' demographic characteristics (e.g., age), in line with previous research [25,69,70]. This indicates that EMDR therapy is consistently effective in reducing depressive symptoms across various conditions.

 

Furthermore, the meta-regression results indicate that depression severity is a significant predictor of EMDR efficacy (z = 2.688; p = 0.007). The subgroup meta-analysis revealed that the effect size of EMDR for mild-to-moderate depression was 0.46 (95% CI: 0.21–0.71), indicating a moderate effect. In contrast, the effect size for severe depression was larger, at 0.99 (95% CI: 0.71–1.26). This suggests that the more severe the depression, the greater the therapeutic effect of EMDR.

 

EMDR may be more effective for severe depression because of various neurobiological mechanisms. First, it may promote neuroplasticity by allowing traumatic memories to be reprocessed, which may help reduce deeply ingrained negative beliefs and rumination [71,72]. Second, it may potentially reduce emotional distress and stabilize emotions by reducing amygdala hyperactivity . Third, EMDR may lead to faster cognitive changes by targeting cognitive distortions and negative self-referential thoughts. It may also regulate the autonomic nervous system, potentially addressing physiological symptoms such as insomnia and chronic stress . In addition, it may enable patients to confront underlying trauma by reducing avoidance behaviors and increase prefrontal cortex engagement, which may improve emotional regulation . Together, these factors suggest that EMDR may be particularly effective in severe depression, especially when trauma is involved.

 

 

4.1. Effects of EMDR on Depression Comorbid with PTSD

 

Previous studies on PTSD have reported that EMDR interventions improve comorbid depression [46,52,57,64,67]. When PTSD was treated with EMDR, comorbid depression showed significant improvement. EMDR has been shown to be more effective than waiting-list controls [46,52,57-61,65,67], no treatment, and even pharmacotherapy with antidepressants (e.g., fluoxetine) . EMDR has also been reported to have effects similar to those of exposure therapy [59,76-78]. Other studies have likewise found that, compared with cognitive behavioral therapy (CBT), EMDR has a similar effect in improving comorbid depression, with no significant difference between the two interventions [57,79,80].

 

 

While these studies establish the short-term efficacy of EMDR, the importance of long-term outcome studies is increasingly recognized for fully understanding its lasting effects, particularly in the context of depression. A study evaluating the long-term effects of EMDR on adult female survivors of childhood sexual abuse provides important evidence in this regard . The results show that the benefits of EMDR for depression and trauma-related symptoms persisted 18 months after treatment, with participants continuing to demonstrate significant improvements in Beck Depression Inventory scores. This suggests that the therapeutic effects of EMDR are not merely immediate but also persist over the long term, offering a more robust solution for trauma-related depression . These long-term findings emphasize the importance of further research into how EMDR can continue to provide lasting benefits for depression, particularly in individuals with a history of trauma. This is crucial for expanding the clinical application of EMDR and refining treatment protocols to maximize long-term efficacy.

 

4.2. Efficacy of EMDR for Major Depressive Disorder

 

EMDR has been reported to be effective in treating major depressive disorder (MDD), even in the absence of comorbid PTSD. A case study involving two adolescents with mild-to-moderate depression found that EMDR significantly reduced depressive symptoms and that remission was maintained for 2–3 months after treatment . Another case study reported successful recovery in a patient with severe depression after three months of EMDR therapy, and a patient with depression comorbid with ADHD experienced improvement substantial enough to discontinue medication following treatment . In addition, a woman with chronic depression resistant to antidepressants reported complete resolution of depression after nine EMDR sessions, with improvement maintained for six months .

 

 

RCTs have also demonstrated EMDR efficacy in treating MDD [27,49,50,86-88]. A large-scale RCT conducted in six European countries involving 30 patients with recurrent depression found that the group receiving EMDR alongside standard treatment showed greater improvement in depression than the group receiving standard treatment alone . Gauhar et al. (2016) found that 26 participants diagnosed with MDD showed significant improvement in depressive symptoms and a reduction in negative cognitions after 6–8 EMDR sessions. These improvements were maintained at a three-month follow-up, suggesting that EMDR may be an effective long-term treatment for depression .

 

Combining EMDR with other treatments for depression may significantly improve treatment outcomes. Hofmann et al. (2014) reported that EMDR combined with CBT resulted in higher remission rates and greater reductions in depressive symptoms than CBT alone . This suggests that EMDR may be particularly effective in addressing the trauma-related components of unipolar depression. Similarly, in the European Depression EMDR Network Randomized Controlled Trial (EDEN), Ostacoli et al. (2018) found that EMDR, when used alongside antidepressant medication, led to slightly better outcomes in reducing depressive symptoms than the combination of CBT and antidepressant medication, particularly in patients with recurrent depression . Hase et al. (2018) also found that EMDR produced better outcomes than medication alone, particularly in treatment-resistant depression, by improving emotional regulation and processing unresolved trauma .

 

The rationale for combining EMDR with other treatments lies in its ability to address trauma-related aspects of depression that may not be fully resolved through cognitive restructuring in CBT or pharmacotherapy alone. EMDR complements these treatments by reprocessing unresolved traumatic memories, helping to reduce emotional distress and improve overall treatment outcomes. This multimodal approach suggests that EMDR may be a valuable adjunctive treatment, particularly for treatment-resistant or trauma-related depression. Further research is needed to identify the most effective combinations and optimize treatment protocols for different types of depression.

 

 

4.3. Mechanism of EMDR in Treating Depression

 

The Adaptive Information Processing (AIP) model explains the therapeutic effects of EMDR on depression . According to the AIP model, if negative experiences associated with stressful events are not adequately processed, they may become “frozen” in the brain, retaining their original emotions, thoughts, and sensations. These maladaptively processed memories can be triggered by internal or external stimuli, leading to distorted thoughts or emotions and potentially contributing to mental disorders such as depression . Barry et al. (2006) proposed that depression is closely associated with a memory bias in the implicit memory system, with negative self-related information being more accessible than positive information . This bias reinforces a negative self-concept and contributes to the persistence and worsening of depressive symptoms. Dysfunctional memories resulting from incomplete processing lack “memory awareness,” meaning that the emotional aspects of these memories have not been properly integrated .

 

 

EMDR therapy helps reprocess these dysfunctional memories using eye movements or other forms of bilateral stimulation. This process affects the brain's neural networks, allowing dysfunctional memories to be integrated into existing semantic associations [90,91]. Specifically, EMDR activates the brain's information processing system through bilateral stimulation, helping repressed or incompletely processed memories to be properly integrated. This reduces the emotional burden of memories, changes negative self-concept, and alleviates depressive symptoms . EMDR also provides a safe environment for patients to express and process repressed or unprocessed emotions, which may be particularly beneficial for those with depression. As these repressed emotions are resolved, depressive symptoms may subside .

 

Some researchers have proposed that EMDR facilitates the reprocessing and integration of traumatic memories by inducing brain states similar to those experienced during specific sleep stages (e.g., Rapid Eye Movement, REM) [92,93]. During REM sleep, the brain reactivates memories, reduces their emotional intensity, and integrates them into broader semantic memory networks. EMDR is believed to induce a brain state similar to REM sleep, in which memories are reactivated, desensitized, and integrated into broader memory networks, thereby reducing the emotional burden of traumatic memories and promoting psychological recovery . While Stickgold et al. (2002) proposed that EMDR mimics REM sleep, Pagani and Carletto (2017) suggested that EMDR may also induce a state similar to slow-wave sleep (SWS), which is crucial for memory consolidation and emotional processing . Both theories emphasize EMDR's ability to harness natural sleep-related mechanisms to reduce the emotional impact of traumatic memories and promote psychological recovery.

 

4.4. Neural Mechanisms of EMDR in Treating Depression

 

The neural mechanisms of EMDR play an important role not only in treating PTSD but also in addressing depression. In particular, key brain regions activated by EMDR overlap with those implicated in depression. During EMDR therapy, alternating bilateral stimulation enhances the function of the prefrontal cortex and anterior cingulate cortex by modifying the neural networks activated during memory reprocessing [71,73]. These regions are critical for emotional regulation and decision-making, and their function is often impaired in depression. Specifically, EMDR increases blood flow in these regions, which is directly associated with the alleviation of depressive symptoms [71,94,95]. Furthermore, by activating these brain regions through bilateral stimulation, EMDR enables the reprocessing of traumatic memories stored in dysfunctional neural networks. This reduces the intensity of negative memories that contribute to depressive symptoms and promotes neuroplasticity, allowing the brain to form new, adaptive neural connections [71,73]. EMDR also affects theta cordance, a neural marker associated with depression, which shows significant reductions correlated with improvements in depressive symptoms after treatment . This suggests that EMDR plays a key role in modulating the imbalanced cognitive and emotional processes seen in depression.

 

The neuroplasticity promoted by EMDR reduces emotional responses linked to past negative memories and facilitates the formation of more adaptive memories. Long-term potentiation and long-term depression mechanisms play a crucial role in this process . These mechanisms help patients with depression move away from negative emotional responses and develop more realistic and positive neural connections. Consequently, EMDR is effective in treating depression because these neural mechanisms enhance emotional regulation and memory reprocessing. Through these processes, EMDR may reduce the negative thoughts and emotional distress that characterize depression and potentially contribute to long-term psychological stability.

 

4.5. Limitations

Although the results suggest that EMDR may be effective in treating depression, several limitations should be considered. One limitation of the selected studies is the inconsistency in depression diagnosis across studies. Only 5 of the 25 studies explicitly diagnosed participants with depression, while the remainder assessed subclinical depressive symptoms. Because subclinical symptoms differ from clinical depression in terms of severity and treatment, this distinction may affect the interpretation of the results. Furthermore, the lack of detailed information on participants' depression histories, such as age at onset, number of major depressive episodes, and distinctions between MDD and bipolar disorder, limits the depth of the analysis. Had such data been available, they would have allowed a more nuanced understanding of EMDR efficacy across different depressive profiles and provided clearer insights into its effects on specific patient subgroups. Future studies should ensure more consistent diagnostic criteria and collect detailed depression histories to better assess the effect of EMDR on clinically diagnosed depression.

 

Another limitation is that, despite the meta-regression confirming that sample size did not significantly affect EMDR efficacy, most studies included in this meta-analysis had small sample sizes, which may exaggerate treatment effects and limit generalizability. In addition, potential biases in the methodologies of the selected studies, such as incomplete randomization and lack of double-blinding, may compromise the reliability of the results.

 

 

Furthermore, although several included studies reported long-term outcomes, this meta-analysis assessed only the immediate effects of EMDR. However, the follow-up periods in these studies varied substantially in both duration and timing. This variability made it impossible to combine long-term outcomes in a coherent meta-analysis. Consequently, this analysis could not determine how effective EMDR remains over an extended period. This limitation highlights the need for future research with more standardized follow-up periods to better evaluate the sustained effects of EMDR on depression.

 

 

4.6. Recommendations

 

In light of research on the use of EFT for depression, several recommendations can be made. First, further investigation of the neural mechanisms underlying the effects of EFT on depression is crucial. Current findings suggest that EFT may alter brain connectivity in areas associated with emotional regulation and mood, but further studies are needed to understand how EFT specifically affects brain circuits associated with depressive symptoms. Furthermore, given the positive outcomes in treating depression, EFT should be integrated into broader, multimodal treatment plans. As a nonpharmacological intervention, EFT may complement existing treatments such as CBT or medication, particularly for treatment-resistant depression. In addition, although EFT is well documented for psychological conditions such as anxiety and PTSD, further research is needed to evaluate its efficacy in treating physiological conditions frequently comorbid with depression, such as heart disease and cognitive disorders. Finally, incorporating EFT into primary healthcare is recommended. As a safe, rapid, and effective method of treating depression, it may provide lasting symptom relief with minimal side effects. Its integration into mainstream healthcare would provide an additional tool for managing depressive disorders, particularly for patients who prefer non-drug treatments. These recommendations will help expand the understanding and use of EFT in treating depression.

 

 

4.7. Conclusions

This systematic review and meta-analysis highlights the efficacy of EMDR in treating depression, extending its application beyond PTSD. The findings indicate that EMDR is consistently effective in reducing depressive symptoms, with larger effects observed in individuals with severe depression. The meta-regression analysis confirmed that variables such as number of sessions and participant demographics did not significantly influence therapeutic efficacy, suggesting that EMDR can be broadly applied across different populations.

 

While this study confirms the utility of EMDR in managing both comorbid PTSD and stand-alone depressive disorders, limitations such as small sample sizes and inconsistent follow-up periods highlight the need for more robust, standardized research. Analysis of neural mechanisms provides insight into how EMDR may influence brain functions associated with emotional regulation and memory processing, offering a scientific basis for its therapeutic effects on depression. Future research should focus on long-term outcomes and more standardized study designs to evaluate the lasting effects of EMDR on depression. Incorporating EMDR into multimodal treatment approaches and primary care treatment settings, particularly as a nonpharmacological option, may improve treatment outcomes for patients with treatment-resistant depression. These steps will contribute to a broader understanding and use of EMDR as a powerful therapeutic tool for depression.

 

Supplementary Materials: The following supporting information can be downloaded at: https://www.mdpi.com/article/10.3390/jcm13185633/s1, Table S1. Risk of bias. Figure S1. Publication bias result. Figure S2. Results of the trim-and-fill analysis. PRISMA checklist .

 

Author Contributions: J.-W.S. wrote the main manuscript text and analyzed the data. J.-W.S. and J.I.K. collected the data and prepared the figures and tables. All authors have read and agreed to the published version of the manuscript.

 

Funding: This study was supported by the Korea Institute of Oriental Medicine (KSN2312022) and the Ministry of Health and Welfare of the Republic of Korea (HF23C0010).

 

Institutional Review Board Statement: Not applicable to studies not involving humans or animals. This study is a meta-analysis and does not involve direct interaction with human participants or animals.

 

Informed Consent Statement: Not applicable to studies not involving humans or animals. This study is a meta-analysis, and therefore no new data were collected directly from individuals.

 

Data Availability Statement: The data supporting the findings of this study are available from the corresponding author upon reasonable request.

 

Acknowledgments: The authors thank Kahye Kim and Jaeuk U. Kim for their support during the data collection and analysis processes.