The combination of dialectical behavioral skills training with EMDR in the treatment of borderline personality disorder and psychological trauma: a feasibility randomized trial

Abstract

Background

Comorbid borderline personality disorder (BPD) and posttraumatic stress disorder (PTSD) predict poorer treatment outcomes. Available treatments for BPD and psychological trauma are often phase-based, first ensuring stabilization of dysregulated behaviors and emotions and later focusing on treating trauma. This study investigates the feasibility, acceptability, and preliminary efficacy of combining dialectical behavioral therapy group skills training (DBT-ST), consisting of mindfulness, emotion regulation, distress tolerance, and interpersonal-effectiveness skills, with eye movement desensitization and reprocessing (EMDR) individual therapy for patients with BPD and psychological trauma.

Methods

Forty-two participants with BPD and psychological trauma (40 females, mean age = 28.5, SD = 9.2) participated in the study. All participants underwent an initial 6-month DBT-ST group (phase 1), then those randomized to the experimental group received EMDR, and those in the control condition continued DBT-ST (phase 2). Feasibility and acceptability were assessed through qualitative interviews. Additionally, borderline personality disorder symptoms and trauma-related symptoms were measured as secondary clinical outcomes. Assessments were conducted at baseline, post phase 1, and post phase 2.

Results

Overall retention from baseline to post phase 2 was 62%. Descriptively, retention was 81.2% in the DBT-ST continuation group and 72.2% in the DBT-ST+EMDR group, though this difference was not statistically significant. Qualitative interviews suggested that the sequential design was acceptable, and that DBT-ST helped some participants feel more prepared for subsequent trauma-focused work, although these findings are based on a small qualitative subsample. Both conditions reduced BPD symptoms, while only the DBT-ST+EMDR condition significantly reduced dissociative symptoms from baseline to post phase 2.

Conclusions

A definitive, fully powered randomized clinical trial is warranted to confirm these findings and optimize the integration of DBT-ST and EMDR.

Trial registration

Clinical Trials, NCT04856449. Registered on 08-04-2021.

Background

Borderline Personality Disorder (BPD) is a complex, multidimensional disorder characterized by unstable mood, relationships, and impulsivity [1]. BPD arises from a complex interaction of biological and environmental factors. Childhood trauma has been increasingly considered an important risk factor for the development of BPD [2]. Furthermore, BPD diagnoses are more frequent in individuals who have experienced childhood abuse and neglect [3–5]. Epidemiological studies show that up to 50% of patients with BPD also meet criteria for posttraumatic stress disorder (PTSD) [6], with similar findings in clinical BPD samples, of whom 33–79% meet diagnostic criteria for PTSD [7]. Importantly, the comorbidity of BPD and PTSD implies a more significant psychosocial impairment, a lower likelihood of remission from BPD across ten years and predicts higher treatment dropout rates [7–9].

Psychotherapy, particularly dialectical behavior therapy (DBT), is considered the first-line treatment for BPD [1, 10]. A core component of DBT is skills training (DBT-ST), which teaches mindfulness, emotion regulation, interpersonal effectiveness, and distress tolerance strategies [11]. Accumulated research has shown that DBT-ST can reduce life-threatening behaviors and improve impulsivity, anger, and affective dysregulation [11, 12]. DBT conceptualizes treatment as progressing through stages, beginning with the control of life-threatening behaviors, and later addressing trauma and emotional suffering. Treatments for BPD, including DBT, have shown limited efficacy in addressing trauma-related symptoms, underscoring the need to incorporate additional therapeutic modalities that directly target these symptoms [13]. In response to this need, trauma-focused adaptations within the DBT framework have been developed and have shown efficacy in reducing PTSD symptoms [14–16].

Eye movement desensitization and reprocessing (EMDR) is a trauma-focused therapy based on the adaptive information processing model (AIP), which proposes that traumatic experiences may be maladaptively stored when they overwhelm the individual’s capacity for processing [17]. EMDR aims to facilitate reprocessing of these distressing memories through an eight-phase protocol that includes bilateral stimulation, usually rapid eye movements [18]. EMDR is recommended in most international guidelines as a first line treatment for PTSD [19]. Recent studies suggest that trauma-focused treatments, including EMDR, can be delivered safely and effectively in individuals with PD, independently of PTSD status, and even without a formal stabilization phase in all cases [20–22]. However, this literature has largely been conducted in diagnostically heterogeneous personality disorder samples, with only a subset of participants meeting criteria for BPD and often provides limited information about prior psychotherapy exposure or the extent of previous skills-based treatment. As a result, it remains unclear whether a deliberately staged approach may offer practical advantages in patients with BPD and psychological trauma treated in specialized clinical settings, where affective instability, dissociation, and behavioral dysregulation often shape treatment planning.

Sequential or stage-based models have been proposed as valid approaches for complex comorbid presentations, in which treatment first targets the most destabilizing symptoms before addressing secondary or trauma-related difficulties [23, 24]. In these models, treatment often begins with a skills-building phase, followed by trauma-focused work and a later phase of integration. This logic is consistent with standard DBT, which prioritizes the stabilization of life-threatening and severe dysregulated behaviors before addressing trauma-related symptoms [25]. Similarly, DBT-based trauma treatments such as DBT-PE follow a staged approach in which standard DBT precedes trauma-focused intervention [14]. Specifically, in the DBT-PE model [14], trauma work can start once six readiness criteria are met: no imminent suicide risk, no recent suicidal or non-suicidal self-injury, ability to control self-harm urges when triggered, no serious therapy-interfering behaviors, PTSD is the top quality-of-life target and the client wants to treat it now, and the client can experience intense emotions without escaping. In the case of DBT-PTSD model [15] the approach is less dependent on a formal criterion but still describes an initial pretreatment/safety-and-commitment phase where having enough engagement, safety, and treatment structure is required to proceed before trauma processing begins.

To date, DBT and EMDR have mainly been examined when delivered concurrently rather than sequentially. One recent randomized controlled trial compared EMDR alone with EMDR delivered concurrently with standard DBT in patients with PTSD and at least four BPD features, and found no significant between-group differences, with higher dropout in the combined treatment arm [26]. These findings suggest that concurrent administration may not necessarily confer additional benefit, but they do not address whether a sequential model may be feasible or acceptable in a specialized BPD population. The aim of the present feasibility study was to test whether a sequential DBT-ST followed by EMDR approach is feasible, acceptable, and associated with promising preliminary clinical change in patients with BPD and psychological trauma. Findings from this study are intended to inform the design of a future fully powered randomized clinical trial.

Methods

Study design

This is a unicentric, feasibility RCT with two treatment arms: (1) DBT-ST + DBT-ST, and (2) DBT-ST+EMDR. Patients were recruited at an outpatient, public specialized BPD Unit in Spain. A formal sample size calculation was not used, as we anticipated that this sample size would provide sufficient information on the study objectives to inform a future larger trial. Upon confirmation of eligibility, participants were randomized into two treatment arms: DBT-ST + DBT-ST or DBT-ST+EMDR. A computer-generated randomization list was obtained to assign participants to each treatment arm. All participants initially underwent a six-month DBT-ST training (phase 1). Following this, participants in the DBT-ST + DBT-ST group received an additional six months of DBT-ST, while those in the DBT-ST+EMDR group received up to 16 individual EMDR sessions (phase 2). A blinded trained psychologist performed all assessments.

Each intervention arm was supervised by a clinical supervisor who met regularly with therapists throughout the study to ensure treatment adherence to the respective protocols. For the EMDR condition, supervision was provided by a certified EMDR consultant/therapist (W Lupo), and for the control condition, supervision was provided by a senior DBT therapist (MJ Campins). These supervision meetings focused on protocol adherence, case review, and addressing clinical challenges to maintain treatment fidelity.

Quantitative assessments were conducted at three time points: baseline, post phase I (DBT-ST), and post phase II (DBT-ST + DBT-ST or DBT-ST+EMDR). All participants were assessed post-treatment within one week after completing phase 2. At post phase 2, participants in the DBT-ST+EMDR condition were invited to provide feedback on the treatment through individual in-depth interviews; of the 18 participants, only 11 were reachable, and 7 of them agreed to participate.

The study was recorded in the ClinicalTrials.gov trial register (NCT04856449; registered on 08-04-2021), approved by the Clinical Research Ethical Committee of the Hospital de la Santa Creu I Sant Pau, Barcelona (Protocol number: IIBSP-TLP-2020-105), and was conducted under the Declaration of Helsinki.

Participants

Individuals were eligible if they met the following criteria: (1) age 18–60 years, (2) diagnosis of BPD according to DSM-IV criteria (assessed with the SCID-II and DIB-R), (3) history of adverse childhood experiences (assessed with the CTQ-SF; a positive history of childhood maltreatment was defined as scoring in the moderate or severe range on at least one of the five CTQ-SF subscales) and/or current PTSD symptoms (assessed with the EGEP-5; participants qualified if they endorsed any PTSD symptoms, regardless of whether they met full diagnostic criteria); and (4) provision of written informed consent. Exclusion criteria were: (1) lifetime diagnosis of schizophrenia, drug-induced psychosis, organic brain syndrome, bipolar disorder, or mental retardation; and (2) receiving any other psychotherapeutic treatment at the time of inclusion or having previously undergone DBT-ST or EMDR. Participants were allowed to continue their usual medications before study enrollment; however, no changes in medication type or dosage were permitted during the study period.

Measures

Diagnostic measures

An ad hoc questionnaire was used to collect data on sociodemographic and clinical characteristics (e.g., age, gender, marital status, educational level, and pharmacological treatment). BPD diagnosis was assessed using the Structured Clinical Interview for DSM Axis II Disorders (SCID-II) [27], a semi-structured interview designed to evaluate DSM-IV personality disorders. The Spanish version [28] demonstrated adequate discrimination between personality disorders and good inter-rater reliability. BPD severity over the past two years was assessed with the Spanish version of the Revised Diagnostic Interview for Borderlines (DIB-R) [29, 30], which showed strong psychometric properties (Cronbach’s alpha = 0.89; sensitivity = 0.81; and specificity = 0.94).

Childhood psychological trauma was assessed using the Spanish version of the Childhood Trauma Questionnaire-Short Form (CTQ-SF) [31], a 28-item self-report instrument that retrospectively evaluates five domains of childhood maltreatment: emotional abuse, physical abuse, sexual abuse, emotional neglect, and physical neglect. Items are rated on a five-point Likert scale ranging from “never true” to “very often true”, with subscales scores ranging from 5 to 25; higher scores indicate greater severity of maltreatment. Following the original CTQ-SF manual, cut-off scores were applied to classify each subscale into four severity levels: none/minimal, low, moderate, and severe (i.e., cut-off scores of 8 or higher for sexual abuse, 10 or higher for physical abuse, 13 or higher for emotional abuse, 10 or higher for physical neglect, and 15 or higher for emotional neglect [31].

The presence and severity of current probable post-traumatic stress disorder, according to DSM-5 criteria, were assessed using the Global Assessment of Posttraumatic Stress Scale (EGEP-5) [32]. The instrument consists of three sections: (1) Events, which provides information relevant to Criterion A for PTSD-DSM-5 diagnosis. This section includes a checklist of 11 traumatic events plus an additional open-ended category, and participants are asked to indicate which events they have directly experienced, witnessed, or learnt had occurred to a close relative or friend. They are then asked to identify the most disturbing event, which serves as the reference point for all subsequent items; (2) Symptoms, which include the 17 DSM-5 PTSD symptoms (criteria B, C, and D: re-experiencing, avoidance/numbing, and arousal), along with two items addressing symptom duration and onset (criterion E), plus 9 additional items assessing subjective clinical symptoms; and (3) Functioning, addressing criterion F. The EGEP-5 has demonstrated strong psychometric performance, with high internal consistency (α = 0.92). Confirmatory factor analysis supported a good model fit for DSM-IV criteria. Total scores reflect PTSD severity, with higher scores indicating more severe symptoms.

Feasibility outcomes

The feasibility of the trial was assessed based on the number of potential participants identified and randomized, as well as data completion at all timepoints. Participants assigned to DBT-ST+EMDR were interviewed at post phase 2 to explore the acceptability of the intervention. They were asked to provide feedback on the program, including perceived facilitations and barriers, and to evaluate whether the intervention improved their mood regulation. Particular attention was given to their views on the combination of DBT-ST and EMDR, as well as any potential differential effects. Treatment adherence was assessed by the number of sessions attended. Dropout rates were defined using two criteria: for DBT-ST, dropout was defined as missing four or more consecutive skills training sessions; for EMDR, it was defined as a unilateral decision to discontinue treatment, regardless of the number of sessions attended. Treatment-related outcomes - including sessions attended, treatment dropout, suicide attempts, and psychiatric hospitalizations- were also collected for each treatment phase.

Symptoms outcomes

The following self-reported questionnaires were used to examine symptom trajectories across each study phase: the Borderline Symptom List (BSL-23) [33], a 23-item self-rated scale assessing the severity of borderline personality disorder. The Spanish version [34] has demonstrated high reliability (Cronbach’s alpha = 0.94) and good test-retest stability.

The Dissociative Experiences Scale (DES) [35] is a 28-item self-assessment tool measuring the frequency of pathological dissociative experiences. Total scores range from 0 to 100, with scores of 30 or above indicating high levels of dissociation. The DES includes three subscales: amnesia, dissociation, and depersonalization.

Interventions

Dialectical behavioral therapy skills training (DBT-ST)

In Phase 1 of the study, DBT-ST was provided to all participants in weekly group sessions lasting 150 min each over six months. Skills training occurs in a group format, providing a structured environment and opportunity to self-regulate, monitor, and manage difficult emotions during sessions while resisting urges to talk or leave the group when inappropriate [36]. DBT-ST aims to increase the patient’s repertoire of efficacious behaviors and reduce problematic ones by teaching four skills: mindfulness, distress tolerance, emotion regulation, and interpersonal effectiveness [11]. Emotional regulation skills help clients understand and manage intense emotions without engaging in life-threatening behaviors. Distress tolerance skills are developed to deal with emotional crises without making things worse, including self-soothing, distraction, acceptance, and crisis survival strategies. Mindfulness is practiced by staying present and grounded in a participative, non-judgmental way. Lastly, interpersonal effectiveness targets increasing efficacy in social interactions, setting boundaries, and building efficacious relationships.

In phase 2 of the study, participants in the DBT-ST + DBT-ST group received an additional six months of DBT-ST, which will allow them to deepen their understanding and mastery of each skill. DBT-ST was delivered by a trained psychologist.

Eye movement desensitization and reprocessing (EMDR)

Patients received up to 16 weekly individual EMDR sessions, each lasting 60 min. EMDR therapy focuses on processing pathogenic memories, which have contributed to the development and maintenance of posttraumatic symptoms. It is assumed that targeting these memories will lead to a reduction of trauma symptoms.

For this study we used the standard EMDR protocol, consisted of eight fixed procedural steps: history and treatment planning (phase 1), preparation, including an explanation of how EMDR works and development of coping strategies (phase 2), and an assessment phase in the that the traumatic incident is accessed through the image that represents the worst part of the event, the identification of the negative beliefs associated with the image, the desirable positive beliefs, the emotions and sensations related to the disturbing event. The level of disturbance in remembering the traumatic incident and the validity of the client’s preferred cognitions are also rated (phase 3). Desensitization and reprocessing occur within phase 4 and represent the core component of the intervention: the client focuses on a dual attentional stimulus (usually eye movements) while connecting to the image, negative beliefs, and sensations associated with the disturbing memory to initiate desensitization and processing of the experience. Once this phase is finished, we install the positive belief (phase 5) and conduct the body scan (phase 6). Phase 7 is dedicated to closure and arranging follow-up, and in phase 8, a reevaluation is conducted. EMDR was delivered by certified EMDR therapists who have received accredited training.

Data analysis

First, independent t-tests for continuous variables and chi-square tests for categorical variables were used to assess possible differences in demographic and clinical measures at baseline. Second, intention-to-treat (ITT) analyses were conducted, including all enrolled participants, regardless of whether they completed the intervention. Missing data were handled using Multiple Imputation by Chained Equations (MICE) with 50 imputations and the Predictive Mean Matching (PMM) algorithm. This approach was chosen to provide more robust estimates and better account for the uncertainty of missing data under the Missing at Random (MAR) assumption. Furthermore, a per-protocol (PP) analysis including only participants who completed the study was conducted as a sensitivity analysis.

Multilevel modeling (MLM) analysis with the restricted maximum likelihood (REML) method was used to evaluate the effects of the intervention on clinical measures (i.e., BSL-23, DES). In each of these analyses, the time (i.e., post phase 1, post phase 2) was considered as a within-subject effect, and the group (i.e., DBT-ST + DBT-ST vs. DBT-ST+EMDR) was regarded as the between-subjects effect, as well as interaction terms (time x group). Participants were considered as random effects (random participants’ intercept). Post hoc analyses were performed using paired Student’s t-tests when significant effects were observed [37]. Descriptive analyses were performed using IBM SPSS Statistics (version 24), while all inferential models were tested with the lme4 package [38]. Multiple imputation procedures were implemented via the mice package [37]. All analyses were conducted within the RStudio environment [39].

Semi‑structured interviews were audio‑recorded, transcribed verbatim and analyzed using a thematic approach. A structured coding framework was developed deductively from the study objectives and relevant literature and then refined inductively as new codes emerged from the data. Two members of the research team independently coded an initial subset of transcripts, compared and discussed discrepancies, and reached consensus on a final codebook, which was then applied to the remaining interviews to develop and refine higher‑order themes.

Results

Baseline characteristics

Recruitment took place between September 2021 and September 2023. Figure 1 presents a flow diagram of recruitment and retention outcomes. A total of 57 potential participants were assessed for eligibility, of whom 42 were finally randomized.

Fig. 1.

Flow chart diagram of participants. PP = Per protocol, ITT = Intention to Treat

Table 1 displays the socio-demographic characteristics of the sample (no significant group differences were observed). The final sample included 42 participants (40 women), with a mean age of 28 years (SD = 9.27). At baseline, a substantial proportion of the participants had completed post-secondary education. Approximately one-third were employed, one-third were unemployed, and one-third were students. On average, participants scored seven points (SD = 1.17; range: 6–10) on the diagnostic interview for BPD (DIB-R). Most patients (n = 36; 85.7%) were receiving psychiatric treatment, primarily antidepressants (n = 23, 78.6%).

Table 1.

Baseline sociodemographic and clinical characteristics of participants by intervention group

	Total sample	DBT-ST + DBT-ST	DBT-ST+EMDR
	(n = 42)	(n = 21)	(n = 21)
Age, mean (SD)	28.55 (9.27)	30.33 (10.31)	26.76 (7.96)
Sex, female, n (%)	40 (95.2)	21 (100)	19 (90.5)
Educational level, n (%)
Middle school  High school	3 (7.1) 26 (61.9)	1 (4.8) 12 (57.1)	2 (9.5) 14 (66.7)
University	8 (19)	6 (28.6)	2 (9.5)
Postgraduate	5 (11.9)	2 (9.5)	3 (14.3)
Employment status, n (%)
Unemployed	11 (26.2)	5 (23.8)	6 (28.6)
Employed	12 (28.6)	7 (33.3)	5 (23.8)
Student	12 (28.6)	6 (28.6)	6 (28.6)
Sick leave / disability	7 (16.7)	3 (14.3)	4 (19)
Pharmacological treatment, n (%)	36 (85.7)	20 (95.2)	16 (76.2)
Antidepressants	33 (78.6)	19 (90.5)	14 (66.7)
Anxiolytics	19 (45.2)	11 (52.4)	8 (38.1)
Mood Stabilizers	9 (21.4)	6 (28.6)	3 (14.3)
Antipsychotics	19 (45.2)	12 (57.1)	7 (33.3)
DIB-R total score, mean (SD)	7.07 (1.17)	7.10 (1.17)	7.05 (1.20)
EGEP-5, n (%)
PTSD diagnosis	37 (88.1)	17 (81)	20 (95.2)
Depersonalization	25 (59.5)	13 (61.9)	12 (57.1)
Derealization	31 (73.8)	14 (66.7)	17 (81)
EGEP-5, symptom level, n (%)
Low-Medium	18 (42.9)	11 (52.4)	7 (33.3)
Medium-High	24 (57.1)	10 (47.6)	14 (66.7)
CTQ-SF, mean (SD)
Emotional Abuse	16.28 (6.23)	15.16 (5.51)	17.30 (6.80)
Physical Abuse	9.18 (5.03)	7.55 (2.79)	10.65 (6.13)
Sexual Abuse	8.78 (4.66)	9.88 (4.96)	7.80 (4.25)
Emotional Negligence	15.52 (5.52)	15.50 (4.86)	15.55 (6.19)
Physical Negligence	9.60 (4.31)	9.38 (3.89)	9.80 (4.75)
Total Score	59.39 (20.81)	57.50 (18.62)	61.10 (22.95)
CTQ-SF, moderate-severe scores, n (%)
Emotional Abuse	24 (63.2)	11 (61.1)	13 (65.0)
Physical Abuse	14 (36.8)	4 (22.2)	10 (50.0)
Sexual Abuse	16 (42.1)	11 (61.1)	5 (25.0)
Emotional Negligence	23 (60.5)	12 (66.7)	11 (55.0)
Physical Negligence	16 (42.1)	7 (38.9)	9 (45.0)

Note. DBT-ST + DBT-ST = Dialectical Behaviour Therapy-Skill Training-1 plus Dialectical Behaviour Therapy-Skill Training-2; DBT-ST+EMDR = Dialectical Behaviour Therapy-Skill Training plus Eye Movement Desensitization and Reprocessing Therapy; SD = standard deviation; DIB-R = Revised Diagnostic Interview for Borderlines; EGEP-5 = Global Posttraumatic Stress Evaluation; PTSD = post-traumatic stress disorder; CTQ = Childhood Trauma Questionnaire

The EGEP-5 revealed a wide range of traumatic experiences. Among childhood and adolescent traumas, the most frequently reported were psychological violence by family members (n = 7), followed by sexual abuse (n = 6), bullying (n = 4), physical abuse within the family (n = 4), emotional neglect (n = 3), suicide of a family member (n = 3), and having a family member with mental illness (n = 3). Participants also reported various traumatic experiences in adulthood, including psychological abuse by romantic partners or family members (n = 4), sexual abuse (n = 3), serious physical or mental illness in a family member (n = 3), suicide of a loved one (n = 2), and workplace bullying (n = 1). Most participants met criteria for a probable PTSD diagnosis (n = 37, 88.1%). Symptoms of derealization were reported by 31 participants (73.8%) and depersonalization by 25 participants (59.1%).

Using the CTQ-SF cutoff criteria, most participants reported having experienced moderate to severe emotional abuse (63.2%) and emotional negligence (60.5%).

Trial retention and dropout reasons

Overall retention rate from baseline to the end of phase 2 was 62% for both groups. Retention from baseline to phase 1was 81.0%, meaning that eight participants dropped out during the first phase of DBT-ST. Reported reasons for dropout are given in Fig. 1. A total of 34 participants entered phase 2 of the trial: 16 received continued DBT-ST (DBT-ST + DBT-ST group), and 18 received EMDR (DBT-ST+EMDR group). The retention rate in phase 2 was 81.2% for the DBT-ST + DBT-ST group (n = 3 dropouts), and 72.2% for the DBT-ST+EMDR group (n = 5 dropouts), which was not statistically different.

In DBT-ST phase 2, two patients dropped out due to incompatibility with work or family/stressors, while one participant discontinued without providing a reason. In the EMDR group, three participants cited a combination of emotional dysregulation and current family stressors, while two reported intensified emotional dysregulation and sleeping difficulties because of trauma processing. Among the five participants who discontinued EMDR, three completed the stabilization phase, while two dropped out before its completion. For those who completed EMDR, phases one and two required an average of 4.4 sessions (range: 2–13), while phases three to eight were completed in an average of 9.6 sessions (range: 2–14). One participant in the EMDR group was voluntarily hospitalized due to acute life stressors. No adverse or severe adverse events were reported in either group. Differences between completers and dropouts were examined across baseline sociodemographic and clinical characteristics; no significant differences were found.

Qualitative feedback was obtained from seven (out of 18) participants receiving DBT-ST followed by EMDR. Table 2 offers a summary of the qualitative interviews. Participants clearly distinguished the goals of each intervention. DBT-ST was associated with gaining practical skills, increasing emotional awareness, and fostering acceptance of BPD. EMDR was perceived as trauma focused. The main themes highlighted included the positive impact of DBT-ST on participants’ understanding of BPD, as well as improvements in acceptance, mindfulness, emotion regulation, and distress tolerance. The group format of DBT-ST was also perceived positively, with many participants reporting feelings of connection and normalization, such as “not feeling alone or weird.” Positive effects of EMDR included the sensation of being validated in one’s trauma history and experiencing a reduction in the emotional intensity of trauma-related memories.

Table 2.

Summary of qualitative interviews in participants receiving DBT-ST followed by EMDR (n = 7)

Theme	Description	Illustrative Quotes
Perceived role of DBT-ST	DBT-ST provided practical skills, enhanced emotional awareness, and improved acceptance of BPD. It was seen as essential before trauma processing.	“DBT equipped me with new skills to use in my everyday life.” “ It helped me understand and accept BPD.”
Perceived role of EMDR	EMDR was recognized as trauma-focused, aiming to reduce the intensity of traumatic memories. Some participants reported benefits, while others experienced increased distress.	“There are things I remember, but I don’t remember them with the same intensity as before.” “In EMDR, it was all trauma… I came out a mess.”
Sequential structure (DBT → EMDR)	The phased structure was seen as beneficial. Most participants felt they could not have engaged in EMDR without first completing DBT-ST.	“I wouldn’t have been able to do EMDR if it had come first.”
Group vs. individual format	Group DBT-ST fostered normalization and connection; EMDR was more solitary and emotionally intense.	“In DBT I didn’t feel alone or weird.”
Attribution of improvement	Participants credited DBT-ST more strongly than EMDR for overall improvement. EMDR was seen as narrower in scope.	“DBT helped me manage daily life. EMDR was only about the past.”
Negative experiences with EMDR	Some participants reported increased emotional dysregulation, distress, and sleep disturbances during EMDR.	“Maybe I needed to talk more about myself, not just the trauma.”

All interviewed participants endorsed the sequential structure—DBT first, followed by EMDR—as beneficial. Four of the seven participants explicitly stated that they would not have been able to engage in EMDR if it had been offered first, due to insufficient emotional regulation to begin trauma processing.

Change in clinical measurements during the interventions

Groups did not differ significantly at baseline on the BSL-23, t(40) = − 0.53, p = .59, or on the DES total score, t(40) = − 0.76, p = .44], nor on its subscales: amnesia: t(40) = − 0.54, p = .58, dissociation t(40) = − 0.58, p = .56, and depersonalization t(40) = − 0.60, p = .55.

Based on the intention-to-treat analyses using multiple imputation, a significant main effect of time was found for borderline symptoms at the end of phase 2 (Table 3). Post hoc comparisons indicated that both the DBT-ST + DBT-ST group and the DBT-ST+EMDR group significantly reduced borderline symptoms from baseline to the end of phase 2 (DBT-ST + DBT-ST: β = -15.52, 95%CI = -24.77 - -6.26, p =.001; DBT-ST+EMDR group: β = -13.57, 95% CI = -22.82 − 0.4.31, p =.005; see Fig. 2A).

Table 3.

Fixed effects estimates for BSL-23, DES, and DES subscales using multiple imputation

	Group	Baseline	Post phase 1	Post phase 2	Effects	Analyses
		M (SD)	M (SD)	M (SD)		B (SE)	p-value	[95% CI]
BSL-23	DBT-ST + DBT-ST	54.33 (20.00)	47.51 (22.59)	38.81 (24.92)	Post phase 1	-6.52 (4.78)	0.17	[-15.77–2.73]
	DBT-ST+EMDR	58.29 (12.63)	53.90 (21.49)	44.71 (24.98)	Post phase 2	-15.52 (4.78)	0.001	[-24.77 – -6.26]
					Group	3.95 (6.63)	0.55	[-8.89–16.79]
					Post phase 1x group	2.14 (6.76)	0.75	[-10.94–15.23]
					Post phase 2 x group	1.95 (6.76)	0.77	[-11.13–15.04]
DES	DBT-ST + DBT-ST	34.91 (22.76)	35.13 (22.05)	31.90 (21.60)	Post phase 1	0.22 (3.03)	0.94	[-5.65–6.09]
	DBT-ST+EMDR	40.59 (22.07)	32.18 (16.81)	28.66 (20.38)	Post phase 2	-3.00 (3.03)	0.32	[-8.87–2.87]
					Group	5.67 (6.49)	0.38	[-6.95–18.31]
					Post phase 1x group	-8.62 (4.29)	0.04	[-16.93 – − 0.31]
					Post phase 2 x group	-8.91 (4.29)	0.04	[-17.22 – − 0.60]
Amnesia	DBT-ST + DBT-ST	21.01 (16.62)	17.44 (16.12)	13.81 (11.63)	Post phase 1	-3.57 (3.04)	0.24	[-9.46–2.32]
	DBT-ST+EMDR	24.00 (18.73)	19.40 (15.94)	18.93 (16.93)	Post phase 2	-7.20 (3.04)	0.02	[-13.09 – -1.30]
					Group	2.98 (4.98)	0.55	[-6.67–12.64]
					Post phase 1 x group	-1.02 (4.30)	0.81	[-9.35–7.30]
					Post phase 2 x group	2.13 (4.30)	0.62	[-6.20–10.46]
Dissociation	DBT-ST + DBT-ST	45.83 (26.79)	39.81 (26.14)	39.71 (26.94)	Post phase 1	-6.02 (4.20)	0.15	[-14.16–2.11]
	DBT-ST+EMDR	50.10 (19.67)	48.29 (20.11)	41.81 (21.27)	Post phase 2	-6.11 (4.20)	0.15	[-14.26–2.02]
					Group	4.26 (7.31)	0.56	[-9.93–18.46]
					Post phase 1 x group	4.21 (5.95)	0.48	[-7.30–15.73]
					Post phase 2 x group	-2.16 (5.95)	0.71	[-13.68–9.34]
Desperson	DBT-ST + DBT-ST	32.22 (26.79)	27.94 (25.19)	35.04 (25.77)	Post phase 1	-4.28 (4.80)	0.37	[-13.58–5.01]
	DBT-ST+EMDR	37.43 (29.36)	29.92 (24.14)	29.88 (26.90)	Post phase 2	2.81 (4.80)	0.56	[-6.48–12.11]
					Group	5.20 (8.15)	0.52	[-10.60–21.02]
					Post phase 1 x group	-3.22 (6.80)	0.63	[-16.37–9.93]
					Post phase 2 x group	-10.36 (6.80)	0.13	[-23.52–2.79]

Note. DBT-ST + DBT-ST = Dialectical Behaviour Therapy-Skill Training-1 plus Dialectical Behaviour Therapy-Skill Training-2; DBT-ST+EMDR = Dialectical Behaviour Therapy-Skill Training plus Eye Movement Desensitization and Reprocessing Therapy; BSL-23 = Borderline Symptom List-23; DES = Dissociative Experiences Scale; Desperson = DES-Depersonalization

Fig. 2.

Group trajectories for BSL-23 and DES scores from baseline to post phase 2 (based on mean estimates and errors bars from multilevel models)

For the DES total score, a significant group x time interaction emerged at the end of phase 2. Participants in the DBT-ST+EMDR group showed a significant reduction in dissociative experiences from baseline to the end of phase 2 (β = -11.92, 95% CI = -17.79 - -6.04, p <.001), whereas the DBT-ST + DBT-ST group showed no significant change (β = -3.00, 95% CI = -8.87–2.87, p =.38; see Fig. 2B).

Regarding the DES subscales, for amnesia a significant main effect of time was found from baseline to the end of phase 2 (β = -7.20, 95% CI = -13.09 - -1.30, p =.02), indicating a general reduction in symptoms across both groups, with no significant group x time interaction. For the dissociation subscale, no significant main effects or interactions were observed. For the depersonalization subscale, no significant main effects or group × time interactions were observed.

Per-protocol analyses yielded a broadly similar pattern (Table 4). In these analyses, the time effect for BSL-23 from baseline to phase 2 remained significant in the DBT-ST+EMDR group (β = − 11.43 β=−11.43, 95% CI − 22.09 − 22.09 to − 0.93 − 0.93, p =.04 p=.04), whereas effects on the DES total score and subscales were generally attenuated, with only the group × time interaction for DES total at phase 2 remaining statistically significant (β = − 12.18, 95% CI − 21.83 to − 2.40, p =.01).

Table 4.

Fixed effects estimates for BSL-23, DES, and DES subscales: per-protocol analysis

	Group	Baseline	Post phase 1	Post phase 2	Effects	Analyses
		M (SD)	M (SD)	M (SD)		B (SE)	p-value	[95% CI]
BSL-23	DBT-ST + DBT-ST	55.71 (18.13)	46.63 (23.88)	44.28 (24.73)	Post phase 1	-9.08 (4.86)	0.06	[-18.47 – 0.25]
	DBT-ST+EMDR	59.24 (13.85)	52.72 (20.27)	43.32 (25.14)	Post phase 2	-11.43 (5.47)	0.04	[-22.09 – − 0.93]
					Group	3.52 (6.32)	0.57	[-8.69–15.74]
					Post phase 1x group	2.56 (6.71)	0.70	[-10.31–15.60]
					Post phase 2 x group	-4.48 (7.30)	0.54	[-18.51–9.80]
DES	DBT-ST + DBT-ST	34.91 (22.76)	32.89 (22.59)	34.49 (23.49)	Post phase 1	-2.02 (3.35)	0.54	[-8.46–4.43]
	DBT-ST+EMDR	40.59 (22.07)	32.28 (15.47)	27.98 (21.29)	Post phase 2	− 0.41 (3.78)	0.91	[-7.72–6.84]
					Group	5.67 (6.69)	0.40	[-7.34–18.70]
					Post phase 1x group	-6.28 (4.61)	0.17	[-15.14–2.59]
					Post phase 2 x group	-12.18 (5.03)	0.01	[-21.83 – -2.40]
Amnesia	DBT-ST + DBT-ST	21.01 (16.62)	19.34 (17.54)	19.73 (15.55)	Post phase 1	-1.66 (2.80)	0.55	[-7.08–3.72]
	DBT-ST+EMDR	24.00 (18.73)	17.03 (16.38)	16.20 (17.62)	Post phase 2	-1.27 (2.80)	0.64	[-6.69–4.11]
					Group	2.98 (5.33)	0.57	[-7.38–13.36]
					Post phase 1x group	-5.30 (3.86)	0.17	[-12.72–2.17]
					Post phase 2 x group	-6.52 (3.86)	0.09	[-13.95 – 0.95]
Dissociation	DBT-ST + DBT-ST	45.83 (26.79)	42.35 (27.07)	47.02 (30.14)	Post phase 1	-3.48 (4.06)	0.39	[-11.30–4.33]
	DBT-ST+EMDR	50.10 (19.67)	45.73 (18.22)	39.20 (22.96)	Post phase 2	1.19 (4.59)	0.79	[-7.70–9.99]
					Group	4.26 (7.58)	0.57	[-10.50–19.03]
					Post phase 1x group	− 0.88 (5.59)	0.87	[-11.62–9.90]
					Post phase 2 x group	-12.08 (6.10)	0.05	[-23.79 – − 0.19]
Desperson	DBT-ST + DBT-ST	32.22 (26.79)	26.16 (25.12)	30.04 (27.89)	Post phase 1	-6.06 (4.22)	0.15	[-14.16–2.08]
	DBT-ST+EMDR	37.43 (29.36)	26.58 (23.09)	24.80 (29.46)	Post phase 2	-2.18 (4.76)	0.64	[11.35–6.97]
					Group	5.20 (8.27)	0.53	[-10.89–21.31]
					Post phase 1x group	-4.78 (5.80)	0.41	[-15.95–6.37]
					Post phase 2 x group	-10.44 (6.34)	0.10	[-23.59–1.82]

Note. DBT-ST + DBT-ST = Dialectical Behaviour Therapy-Skill Training-1 plus Dialectical Behaviour Therapy-Skill Training-2; DBT-ST+EMDR = Dialectical Behaviour Therapy-Skill Training plus Eye Movement Desensitization and Reprocessing Therapy; BSL-23 = Borderline Symptom List-23; DES = Dissociative Experiences Scale; Desperson = DES-Depersonalization

Table 3 reports estimated marginal means, fixed effects, and interaction terms for BSL-23 and DES from the multiple imputation analyses, whereas Table 4 presents the corresponding per-protocol analyses. Figure 2 displays the trajectories of outcomes and associated variability over time.

Discussion

The primary objective of this feasibility trial was to evaluate the acceptability and preliminary efficacy of combining sequentially DBT-ST and EMDR in individuals with BPD and psychological trauma. Overall retention across the full treatment sequence (i.e., from baseline to the end of phase 2 approximately 40 weeks) was 62.0%, a rate comparable to or superior to similar interventions for BPD and trauma [14, 15]. When examining retention from phase 2 specifically, retention was 81.2% in the DBT-ST continuation group and 72.2% in the DBT-ST+EMDR group, and this difference was not statistically significant.

Few previous studies have tested comparable designs, which makes direct comparisons difficult. However, in a recently published trial in which EMDR and DBT were delivered concurrently, retention for the combined intervention was around 58% [26], notably lower than in our study. This difference suggests that a sequential approach—beginning with DBT-ST and introducing EMDR only afterward—may be more feasible than concurrent delivery, which could represent possibly a marked therapeutic burden in terms of intensity and treatment dose in a complex-to-treat population.

Although retention rates did not differ significantly between groups, quantitative data and qualitative interviews suggest that the overall intervention was acceptable and that many participants perceived the initial DBT-ST phase as helpful for staying in treatment. All interviewed participants indicated that they would have felt less prepared to initiate trauma work without first learning DBT skills. DBT-ST was consistently described as the component most directly useful for managing daily emotional challenges, whereas EMDR was perceived as more specifically focused on traumatic memories.

In the EMDR group, however, some discontinuities were specifically linked to heightened emotional dysregulation triggered by trauma processing. Previous studies with participants diagnosed with other personality disorders and psychosis have also reported a temporary increase in psychological distress following EMDR or prolonged exposure protocols [40]. Importantly, this distress did not appear to translate into poorer overall treatment outcomes [41, 42].

Although the DBT-ST phase was designed to enhance patients’ capacity to engage with trauma-related content, it may not have been sufficient for all individuals. Some participants may have benefited from the inclusion of DBT anti-dissociative skills [15] or additional preparation before initiating EMDR. The amount of skills practice during group therapy may also have influenced our results, as the effects of DBT skills training on emotion regulation are closely related to the degree of home practice [43]. Furthermore, limited practice could have been compounded by the need for some participants to dedicate several EMDR sessions to stabilization before trauma processing. Unfortunately, skills practice was not assessed in the current study. Future studies should therefore consider establishing explicit entry criteria before initiating EMDR, as has been done in DBT-PTSD protocols. Such criteria could include consistent practice of DBT skills, motivation to engage with traumatic memories, and the use of a personalized distress tolerance toolkit.

In our protocol, EMDR therapists did not receive specific training in DBT-ST, nor were patients given explicit guidance on how to apply DBT skills during trauma processing. Future protocols could explore providing structured instructions on the use of DBT skills within the EMDR phase, which may enhance the effectiveness of the combined intervention. Additionally, future studies might consider incorporating booster sessions or ongoing DBT-ST refreshers throughout EMDR to reinforce emotional regulation capacities and improve treatment tolerability.

While standard EMDR protocols typically range from 12 to 18 sessions, our findings suggest that some individuals may require more sessions to achieve effective trauma reprocessing. Notably, the number of sessions dedicated to EMDR phases I (preparation) and II (stabilization) in this study ranged widely, from 2 to 13. The high number of EMDR sessions dedicated to phase I and II underlines the complexity and instability of BPD patients, even though having received DBT-ST before. In fact, DBT-based protocols for working with trauma suggest an average of 40 individual sessions [15, 40]. Future research should include more sessions of EMDR to be able to reprocess more traumatic events and examine the relationship between treatment length and clinical outcomes to clarify whether dose-dependent effects exist.

Our findings revealed a significant effect of time for borderline symptoms (BSL-23), with improvements across both conditions. In line with previous work by McMain [36], the largest gains in BPD symptoms were observed after phase 1, raising the possibility that participants may benefit from short versions of DBT-ST. Regarding dissociation, group × time interactions showed greater reductions in the DES total score in the DBT-ST+EMDR group than in the DBT-ST + DBT-ST group, whereas effects on specific DES subscales were weaker and not consistently significant, including for depersonalization. Notably, the largest decrease in DES scores occurred during the first phase of DBT-ST, suggesting that DBT-ST plays a major role in improving dissociative symptoms, while the additional contribution of EMDR remains to be clarified in future research. The larger reductions observed in dissociative symptoms and amnesia in the DBT-ST+EMDR condition should be interpreted cautiously, as secondary, exploratory findings from a small feasibility trial with unequal treatment dosage between groups.

The DES appears to be a promising candidate for inclusion in a definitive trial. However, other domains not assessed in this feasibility study – such as clinician-rated PTSD symptoms, difficulties in emotion regulation, quality of life, and functional outcomes- may provide a more comprehensive understanding of treatment effects. These additional outcomes were found to improve in the study by Snoek et al. [44] and could offer important insights into the broader impact of combined DBT-ST and EMDR interventions.

This study has some noteworthy limitations. First, the small sample size limits the generalizability of findings and may introduce bias. Second, follow-up was limited to post-treatment, preventing assessment of the delayed benefits of trauma processing. Third, dropout reasons were not always available, introducing potential reporting bias. Fourth, as is often the case with qualitative data, the participants who agreed to take part in the interviews were predominantly those who had completed the intervention and reported benefits from it. This may have introduced a positive bias, limiting the representativeness of the findings with respect to the overall sample, including those who discontinued treatment or did not perceive improvement. Finally, and no less importantly, the study did not include a post-intervention assessment of PTSD symptoms or PTSD diagnosis loss after EMDR treatment. In future larger DBT-EMDR trials, this needs to be incorporated. Moreover, outcomes were restricted to self-report questionnaires; future research should incorporate clinician-administered measures of PTSD, functional outcomes, and quality of life to provide a more comprehensive understanding of treatment effects.

Conclusions

In conclusion, our findings encourage the need for a larger RCT combining sequentially DBT-ST and EMDR, with an adequately powered sample. These results offer a guidance for optimizing the design of a definitive trial, highlighting several key considerations: (1) refinement of inclusion criteria, particularly through the incorporation of clinician-administered assessment tools to accurately determine the prevalence of PTSD in the sample, (2) adoption of a phase-based approach, in which DBT-ST is delivered before EMDR, (3) clear definition of criteria for progressing to trauma-focused treatment, moving beyond purely sequential delivery to ensure integration between interventions (this includes ensuring a more structured and sustained presence of DBT skills throughout the EMDR phase), (4) broader outcome assessment, including a wider range of symptom domains and longer follow-up periods, to determine the stability of the findings, (5) specifically, post-intervention assessment of PTSD diagnosis to evaluate the impact of the intervention on PTSD and (6) careful consideration of recruitment feasibility and trial timeline when designing a definitive RCT. In the present study, start-up activities were delayed by the onset of the COVID-19 pandemic, which coincided with trial initiation and contributed to an extension of the recruitment period beyond the originally registered completion date. While this delay reflects an exceptional circumstance rather than a structural barrier to enrolment, it nonetheless illustrates the sensitivity of small feasibility trials to operational disruptions. A future powered RCT should incorporate multi-site recruitment to expand the eligible population, pre-specified progression criteria based on observed recruitment rates, and prospectively planned contingency periods within the trial timeline. Given that the pathway from feasibility work to a completed definitive RCT commonly spans several years, early investment in site infrastructure and funding strategy will be essential to ensure the trial is both achievable and conducted within a realistic timeframe.

Abbreviations

BSL-23

Borderline symptom list 23

BPD

Borderline personality disorder

CTQ-SF

Childhood trauma questionnaire short form

DBT-ST

Dialectical behavior therapy skills training

DES

Dissociative experiences scale

DIB-R

Diagnostic Interview for Borderlines Revised

EGEP-5

Global assessment of posttraumatic stress scale

EMDR

Eye movement desensitization and reprocessing

PTSD

Post-traumatic stress disorder

RCT

Randomized controlled trial

SCID-II

Structured clinical interview for disorders-II

Author contributions

JS, ME and JCP designed the study and drafted the initial manuscript. CS and WL provided support for conducting the RCT and organized participant’s assessments. ICG conducted the qualitive interviews. CS analyzed the data. BLA, AVG and VP supervised the study and contributed to the critical revision of the manuscript. All authors read and approved the final manuscript.

Funding

This work was supported by a grant of EMDR Europe (Grant Number: 2020-03).

Data availability

The datasets used and/or analyzed during the current study are available from the corresponding author on reasonable request.

Declarations

Ethics approval and consent to participate

This study was approved the Clinical Research Ethical Committee of the Hospital de la Santa Creu I Sant Pau, Barcelona (Protocol number: IIBSP-TLP-2020-105). Data confidentiality and anonymity was assured, as well as clear instructions about the General Data Protection Regulation (GDPR).

Consent for publication

Not applicable.

Competing interests

The authors declare no competing interests.