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. 2025 May 19;16(1):2495642. doi: 10.1080/20008066.2025.2495642

Brief intensive EMDR therapy for PTSD in adults with mild intellectual disability or borderline intellectual functioning and behavioural problems: a multiple baseline design study

Terapia EMDR breve e intensiva para el TEPT en adultos con discapacidad intelectual leve o funcionamiento intelectual limítrofe y problemas de conducta: un estudio con diseño de línea base múltiple

Anne Versluis a,b,CONTACT, Ad de Jongh c,d,e,f, Liesbeth Mevissen g, Carlo Schuengel h, Lianne Bakkum h, Robert Didden b,i
PMCID: PMC12090259  PMID: 40387140

ABSTRACT

Background: Individuals with mild intellectual disability (MID; IQ 50–70) or borderline intellectual functioning (BIF; IQ 70–85) are at an elevated risk of post-traumatic stress disorder (PTSD), with PTSD symptoms possibly associated with behavioural problems. It is important to test the effectiveness of trauma-focused treatments, such as eye movement desensitisation and reprocessing (EMDR) therapy, for adults with MID–BIF, PTSD, and severe behavioural problems.

Objective: To determine the safety and effectiveness of brief intensive EMDR therapy carried out by a team of rotating therapists in adults with MID-BIF, PTSD, and severe behavioural problems.

Methods: Using a randomised non-concurrent multiple baseline between-subjects design, 11 adults with MID-BIF, PTSD, and severe behavioural problems received a maximum of 16 intensive EMDR sessions twice daily for a maximum of two weeks from six different EMDR therapists. Primary outcome measurements included severity of PTSD symptoms, PTSD diagnostic status, and adverse events. Secondary outcome measurements included the frequency and severity of behavioural problems, presence of adaptive behaviour, and the use of involuntary care. Outcome measurements were assessed at baseline, during the intervention and post-intervention phases, and at the follow-up phases, and subject to randomisation tests for statistical significance.

Results: Intensive EMDR therapy carried out by a team of rotating therapists resulted in significant decreases in PTSD symptoms (Mdifference = 15.84, p < .001) with nine of 11 participants no longer meeting the PTSD diagnostic criteria immediately following treatment and at the 9-week follow-up. Randomisation tests revealed no significant changes in adaptive behaviour, frequency, and severity of behavioural problems. Additionally, no decrease in the use of involuntary care measures was observed. One participant dropped out; no adverse events were observed.

Conclusions: Brief intensive EMDR therapy for individuals with MID-BIF and severe behavioural problems, conducted by a team of rotating therapists, can be done safely and effectively to reduce PTSD symptoms.

KEYWORDS: Post-traumatic stress disorder, intensive EMDR-therapy, rotating therapists, mild intellectual disability, borderline intellectual functioning, rotating therapists

HIGHLIGHTS

  • Intensive EMDR therapy with rotating therapists effectively reduces PTSD symptoms in adults with mild intellectual disability and severe behavioural problems.

  • Nine out of 11 participants no longer met PTSD criteria after treatment.

  • The treatment was safe with no adverse events.

1. Introduction

Individuals with mild intellectual disability or borderline intellectual functioning (MID-BIF; IQ 50-85) may be at an increased risk of developing post-traumatic stress disorder (PTSD) compared to the general population (Mason-Roberts et al., 2018; Mevissen et al., 2020). This elevated risk can be attributed to frequent exposure to traumatic events (McDonnell et al., 2019; Nieuwenhuis et al., 2019) and difficulties in processing these events owing to deficits in adaptive and cognitive functioning (Skelly, 2020). The prevalence of PTSD in this group ranged from 10% to ≥40%, with higher rates observed among individuals living in supported housing (Mevissen et al., 2020; Versluis et al., 2025).

PTSD symptoms in individuals with MID-BIF are similar to those of individuals without intellectual disabilities (Hoogstad et al., 2023; Mevissen et al., 2020). Additionally, these symptoms overlap with behavioural problems such as verbal or physical aggression (Kildahl & Helverschou, 2024; Rittmannsberger et al., 2020). Rittmannsberger et al. (2020) found that the association between trauma exposure and challenging behaviour in individuals with MID-BIF was mediated by the severity and frequency of PTSD symptoms. Partly due to these behavioural problems, PTSD in individuals with MID-BIF often remains undiagnosed (Kildahl et al., 2020) and untreated (Keesler, 2020). Classifying people with PTSD requires more than observing visible behaviour; it requires knowledge of what type of events a person may have been exposed to, and how this is linked to their current symptoms (American Psychiatric Association, 2022). Without such a nuanced approach, individuals with MID-BIF may be directed towards behaviour-based interventions. Such interventions may not treat the underlying problems and when PTSD symptoms persist, restrictive measures are sometimes used as a last resort (e.g. fixation and locked doors) which may lead to more PTSD symptoms. Despite ongoing concerns regarding the efficacy and quality of involuntary care for individuals with intellectual disabilities (Heyvaert et al., 2014, 2015), these practices remain prevalent (Bakkum et al., 2023; Fitton & Jones, 2020), especially in individuals with severe behavioural problems (Hastings et al., 2013). For example, Schippers et al. (2018a, 2018b) found that certain coercive measures were frequently taken, up to 43.6% (audio surveillance), 41.6% (limited access to rooms/areas), and 33% (locking outer doors) for persons residing in assisted living units for people with intellectual disabilities.

Trauma-focused therapeutic approaches such as eye movement desensitisation and reprocessing (EMDR) therapy have shown promising results for individuals in the general population (De Jongh et al., 2024). However, the application of traditional treatments for PTSD in the general population has been found to be associated with high dropout rates, possibly due to symptom exacerbation, which can be challenging to distinguish from the temporary distress inherent in trauma-focused therapy (e.g. Bongaerts et al., 2022; Lewis et al., 2020; Van Woudenberg et al., 2018). Between one-quarter and one-third of the participants undergoing trauma treatment discontinued treatment, with some studies showing even higher dropout rates (e.g. Niles et al., 2018). To address this issue, intensive trauma treatments have been developed, involving multiple therapy sessions per week or even multiple sessions per day, often with different therapists rotating during sessions to maintain treatment intensity. Intensive trauma treatments have been associated with improved therapeutic outcomes in the general population (Hoppen et al., 2023), and these intensive treatments have resulted in low dropout rates. For example, Van Woudenberg et al. (2018) reported a dropout rate less than 3%, whereas Bongaerts et al. (2022) achieved no dropout.

Although intensive trauma treatments have been shown to be effective in children and adolescents with MID-BIF (Ooms-Evers et al., 2021), the effectiveness of intensive EMDR therapy in adults with MID-BIF and severe behavioural problems has not been investigated. Tests of suitable treatment options, such as intensive EMDR therapy, for adults with MID-BIF and severe behavioural problems are urgently needed for this vulnerable population. The purpose of the present study was to determine the safety and effectiveness of intensive EMDR therapy with a team of rotating therapists in adults with MID-BIF and PTSD. We hypothesised that PTSD symptoms and behavioural problems would significantly decline after treatment, and that participants’ adaptive behaviour (i.e. behaviour in daily life, related to PTSD symptoms, such as talking to strangers again; see Methods) would improve, and these changes will persist at the 6-week, 9-week, and 4-month follow-ups. Additionally, we expect that most participants who met the diagnostic criteria for PTSD at pre-treatment will lose their diagnostic status post-treatment and that the intervention will reduce the use of involuntary care in adults with MID-BIF. Furthermore, we expect that EMDR therapy will not be associated with adverse events.

2. Methods

2.1. Design

A non-concurrent multiple baseline between-subjects design (Coon & Rapp, 2018) was used to investigate the effectiveness of intensive EMDR therapy with rotating therapists in 11 adults with MID-BIF and behavioural problems on the severity of PTSD symptoms, PTSD diagnostic status, adaptive behaviour, frequency and severity of behavioural problems, and the use of involuntary care measures. The design contained 11 AB (A = baseline phase; B = post-intervention phase and follow-up measurements) experiments in which participants were randomly assigned to baseline lengths of five, six or seven weeks. The person conducting the randomisation was masked to participants’ identity. The intervention phase consisted of a maximum of two weeks, during which EMDR therapy was administered eight times a week from Monday to Thursday. After the completion of EMDR therapy, there was a three-week post-intervention phase, followed by three follow-up measurements (six weeks, nine weeks and four months after the intervention).

2.2. Participants and setting

Adults with MID-BIF (IQ 50-85) living in supported housing of an ID care service in the Netherlands (‘s Heeren Loo) who were on the waiting list for EMDR therapy were informed of the study by the first author. The inclusion criteria were that the participants were diagnosed with MID or BIF, were at least 18 years old, met the DSM-5-TR diagnostic criteria for PTSD, had severe behavioural problems (classified as Care Intensity Level (in Dutch: Zorg Zwaarte Pakket; ZZP) 7, which represents eligibility for the highest level of care intensity according to the Dutch healthcare authority, indicating the need for intensive support due to severe behavioural problems as described in their client files), and had sufficient Dutch language ability. Each participant had at least one steady professional caregiver involved during the study period. The exclusion criteria were high suicidal risk and excessive alcohol/drug use which would make it difficult for a participant to attend a therapy sober.

Participation in this study was voluntary. The study protocol was approved by the Medical Research Ethics Committee of the East Netherlands (reference number: 2020-6967- NL75909.091.20). All clients interested in participating in the study received an information letter. Nine participants provided written informed consent to participate in this study. Because of a lack of capacity to provide written consent, legal representatives provided consent for three participants. However, these three participants still provided verbal consent. This resulted in an initial sample of 12 participants. One participant dropped out on the second day of EMDR therapy because he felt overwhelmed by the emotional stress and refused to further participate in this study. Six women and five men aged 21–65 years, participated in this study. Table 1 presents the characteristics of the participants.

Table 1.

Participant characteristics, treated events, and number of sessions.

Participant Sex Age category DSM diagnoses / syndrome (other than PTSD or MID-BIF) IQ EMDR therapy before  Treated traumatic and stressful memories (number of memories treated) Number of sessions
1 Male 30–35 Other DSM diagnosis TIQ: 61
VCI: 66
PRI: 81
WMI: 55
PSI: 48		 No Placed out of home (1)
Bullied (2)
Aggression in living environment (6)
Parents divorced (1)
Verbal aggression at home (1)		 15
2 Female 20–25 Other DSM diagnoses and syndrome TIQ: 65
PIQ: 50
VIQ: 65		 Yes, but therapy not completed Sexual violence (1) 16
3 Male 25–30 Other DSM diagnosis and syndrome TIQ: 79
VCI: 79
PRI: 98
WMI: 77
PSI: 81		 No Seen unpleasant images on social media (1)
Bullied (2)
Victim of aggression on the street (1)
Dead pet (1)
Returning nightmare (1)
Police related incidents (2)		 9
4 Male 25–30 Other DSM diagnosis TIQ: 69 Yes, but there are untreated traumatic or stressful events. Domestic violence (2)
Bullied (1)
Sexual violence (1)
Involuntary care (1)
Severe storm (1)
Parents divorced (1)
Verbal aggression at home (2)
Witnessed (traffic) accident (1)		 16
5 Female 40–45 No other DSM diagnosis or syndrome TIQ: 69
PIQ: 70
VIQ: 68		 No Illness of a family member (1)
Domestic violence (2)
Bullied (2)
Sexual violence (1)
Verbal aggression at home (1)
Dead pet (1)
Serious physical injury (2)		 16
6 Female 35–40 No other DSM diagnosis or syndrome - Yes, but there are untreated traumatic or stressful events. Illness of a family member (1)
Placed out of home/ to a crisis location (1)
Domestic violence (1)
Sexual violence (2)
Parents divorced (1)
Witnessed (traffic) accident (1)
Serious physical injury (1)		 11
7 Female 25–30 No other DSM diagnosis or syndrome TIQ: 50 Yes, but therapy not completed. Natural death of relative (1)
Not taken seriously (1)
Placed out of home (1)
Domestic violence (3)
Sexual violence (1)
Parents divorced (1)
Involvement in drug trafficking (2)
Verbal aggression at home (3)
Mother arrested (1)
Forced by mother to steal money (1)		 12
8 Female 25–30 No other DSM diagnosis or syndrome TIQ: 50 No Illness of a family member (1)
Domestic violence (2)
Sexual violence (1)
Dead pet (1)
Seeing mother cut herself (1)		 12
9 Male 65–70 Other DSM diagnosis TIQ: 56
PIQ: 50
VIQ: 58		 No Illness of a family member (1)
Natural death of relative (3)
Not taken seriously*
Placed out of home (1)
Domestic violence*
Bullied*
Sexual violence (1)
Aggression in the residential group*
Involuntary care (1)
Been in prison (1)
Parents divorced (1)
Accused of sexual abuse (1)
Girlfriend breaks up (1)		 13
10 Female 40–45 Other DSM diagnoses TIQ: 61
PIQ: 64
VIQ: 58		 No Domestic violence (2)
Bullied (3)
Sexual violence (2)
Aggression in the residential group (3)
Involuntary care (3)
Been in prison (1)
Epileptic seizure (1)
Hearing of voices (1)
Severe storm (1)
Medical procedure (1)		 11
11 Male 20–25 Other DSM diagnosis TIQ: 65
PIQ: 73
VIQ: 63		 No Illness of a family member (1)
Natural death of relative (1)
Not given enough attention (1)
Not taken seriously (3)
Placed out of home (1)
Placed to crisis location (1)
Seen unpleasant images (2)
Domestic violence (3)
Bullied (1)
Seen a burning house (1)
Arrested by the police (1)
Victim of aggression on the street (2)		 11
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Note. TIQ = Total IQ; VCI = Verbal Comprehension Index; PRI = Perceptual Reasoning Index; WMI = Working Memory Index; PSI = Processing Speed Index; PIQ = Perceptual IQ; VIQ = Verbal IQ.

* There are no details regarding the number of different memories processed.

2.3. Measures

In this study, the primary and secondary outcome measurements were assessed. The frequencies used for these measurements are listed in Table 2. The descriptive statistics of the outcome measurements are listed in Table 3.

Table 2.

Overview of measurements by phase and frequency.

Measurement Frequency
Participants’ safety (electronic client file) Extracted by phase
PTSD symptoms (TS-ID) Twice weekly during all phases and follow-ups
PTSD classification (DITS-ID) First week of baseline, first and last days of intervention, last week of post-intervention, and three follow-ups
Adaptive behaviour (GAS) Daily (morning and afternoon) during all phases and follow-ups
Behavioural problems (BPI) Once weekly during all phases and follow-ups
Involuntary care (electronic client file) Extracted by phase
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Note. DITS-ID = Diagnostic Interview Trauma and Stressors – Intellectual Disability Adult Version; TS-ID = Trauma Screener – Intellectual Disability; GAS = Goal Attainment Scaling; BPI = Behavior Problems Inventory.

Table 3.

Descriptive statistics.

Outcome n M SD
PTSD symptoms (TS-ID) 257 25.67 15.98
Adaptive behaviour (GAS) 1164 6.08 77.28
Behavioural problems (BPI) – frequency 152 12.46 11.43
Behavioural problems (BPI) – severity 149 11.51 12.00
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Note. n = total number of measurements.

2.3.1. Primary outcome measures

2.3.2. PTSD symptoms

The symptom section of the self-report measure Trauma Screener – Intellectual Disability (TS-ID; Versluis et al., 2025) was used to assess PTSD symptoms. This section consists of 20 questions scored on a 4-point Likert scale (0 = never, 1 = sometimes, 2 = often, 3 = almost always). The total symptom frequency score (range 0-60) was obtained by summing the scores of the 20 questions, in which questions 9, 10, and 15 were divided into several sub-questions. For the latter questions, only the highest score was recorded in the final score. Higher scores indicate greater levels of PTSD symptoms. The TS-ID has good psychometric properties, including high internal consistency and excellent validity for distinguishing PTSD in adults with MID-BIF based on the outcomes of the DITS-ID (Versluis et al., 2024). Participants completed the symptom questions of the TS-ID, with the DITS-ID timeline (see DITS-ID) placed next to the TS-ID, which provided a clear visual cue for the (traumatic and stressful) events. A professional caregiver was present to explain the items of the TS-ID if needed.

2.3.3. DSM-5-TR PTSD diagnostic status

PTSD diagnostic status was assessed using the Diagnostic Interview Trauma and Stressors – Intellectual Disability – Adult Version (DITS-ID; Mevissen et al., 2018). This clinical interview takes approximately 45–60 minutes to complete and is used to classify DSM-5-TR PTSD. The first section consists of 31 questions (yes/no/other) regarding Type A and stressful life events (not meeting the A-criterion but are experienced negatively by the person). The symptom section includes 39 PTSD symptom questions (PTSD criteria B, C, D, and E) and four questions on potential atypical trauma symptoms (yes/no/other). Subsequently, a thermometer card is used to support the person in indicating impairment in daily life on a scale from 0 (totally not) to 8 (very much). If the interference score is four or higher (criterion G), the participant is asked when the symptoms started to confirm if they have been present for over a month (criterion F). Finally, the interviewer checks if the symptoms are not due to medication, drug use, medical conditions, or somatic disorders (criterion H). There are several versions of the DITS-ID. This study used the adult version and follow-up measurements, which takes approximately 15 min. First, the participant is asked whether the participant has experienced a traumatic or stressful event since the last DITS-ID administration, followed by symptom questions and the thermometer card. The DITS-ID adult version has good psychometric properties, with high internal consistency, good-to-excellent interrater reliability, and good construct validity (Mevissen et al., 2020; Versluis et al., 2024). All DITS-ID interviews were conducted by trained master's students and an independent psychologist.

2.3.4. Participants’ safety

The safety of the participants was defined as the absence of adverse events, including increased suicidal ideation or being placed in a crisis intervention facility. All recorded adverse events were extracted from the participants’ electronic client files.

2.3.5. Secondary outcome measures

2.3.5.1. Adaptive behaviour

Goal Attainment Scaling (GAS) was used to monitor adaptive behaviour on a 6-point scale (−3 = regression, – 2 = initial situation, – 1 = less than the target, 0 = target, + 1 = more than the target, + 2 = much more than the target). Adaptive behaviour was defined in agreement with the participant, professional caregiver, and their psychologist and focused on (for the professional caregiver) observable behaviours that the participant was expected to be capable of without PTSD. Adaptive behaviour was determined for each participant prior to EMDR therapy, and professional caregivers scored the GAS scale daily (twice a day, in the morning and afternoon).

2.3.5.2. Behavioural problems

The Behavior Problems Inventory (BPI; Rojahn et al., 2001) indexes the frequency and severity of a problem behaviour. Both the frequency and severity scores can be derived from the total BPI score. The frequency score of the problem behaviour (51 items) was measured on a 5-point Likert scale (0 = never, 1 = monthly, 2 = weekly, 3 = daily, and 4 = hourly). The severity score of the problem behaviour (51 items) was measured on a 3-point Likert scale (1 = mild problem, 2 = moderate problem, 3 = severe problem). Total scores for both frequency and severity were calculated, with higher scores denoting more frequency/severity of problematic behaviour. In our study, we used the Dutch version of the BPI, which has adequate to good psychometric properties including good inter-rater, intra-rater, internal consistency, and convergent validity (Dumont et al., 2014). A professional caregiver who had regular contact with the participants completed the BPI.

2.3.5.3. Involuntary care

Involuntary care measures is defined as: ‘Any care opposed by a client or client-representative’ (Staatsblad, 2018) and were recorded by professional caregivers of the participants in the ‘Involuntary care reporting system’ in clients’ electronic files. This system was documented for each participant, and both predetermined (multidisciplinary agreed) involuntary care (e.g. ‘bedroom door locked at night’) and incidents of involuntary care (e.g. ‘fixation by professional caregivers’). A study by Schippers et al. (2018a, 2018b) on the ‘Involuntary Care Reporting System’ of ‘s Heeren Loo demonstrated that involuntary care could be reliably recorded with this system. All recorded involuntary care was extracted from participants’ electronic client files.

2.4. Intensive EMDR-therapy and procedure

The participants received EMDR therapy twice daily for a maximum of two weeks from six therapists. Three therapists were certified ‘EMDR Europe practitioners’, while the other three had completed the basic and advanced EMDR courses accredited by the Dutch EMDR Association. All therapists had treated at least 20 clients with MID-BIF for PTSD before the start of the study. The authors were not involved as therapists in the current study. Treatment integrity was monitored by the first author and an accredited supervisor from the Dutch EMDR Association (third author) through three supervision sessions during the baseline phase and three supervision sessions during the intervention phase. These sessions involved reviewing the video recordings and discussing the cases to ensure adherence to the treatment protocol.

A week before therapy (baseline), the professional caregivers and, if possible, the client’s relative received psychoeducation about PTSD and EMDR therapy. Therapy sessions were conducted twice daily (morning and afternoon) from Monday to Thursday, over a two-week period. During the first therapy session (60 min), a case conceptualisation based on the timeline of the DITS-ID was established. For this case conceptualisation, all traumatic (meeting A-criterion) and stressful events (not meeting A-criterion) on the timeline were assessed for distress using a scale for the Subjective Units of Disturbance (SUD) 0 = no distress to 10 = extreme distress and were ordered from high to low SUD. This resulted in a list of traumatic and stressful events that could be treated (case conceptualisation). The first therapy session included psychoeducation for participants about PTSD and EMDR therapy. Participants were not trained in the use of coping skills or emotion regulation techniques prior to treatment (De Jongh et al., 2016). After the first session, all subsequent sessions consisted of 60 min of EMDR therapy. We used the EMDR therapy protocol for children and adolescents up to 18 years of age (De Roos et al., 2021). This protocol includes the same eight phases as the standard protocol developed by Shapiro (2018) but is adapted for individuals with lower language skills, such as individuals with MID-BIF. If necessary, cognitive interweaves were applied as described by Shapiro (2018). In line with the working memory theory (see De Jongh et al., 2024, for a review), working memory taxation during EMDR therapy was achieved using several tasks, specifically eye movements (following fingers or a light bar), which were combined with pulsators. If the participant was unable to perform eye movements, an additional distracting task, such as tapping, counting, or a simple calculation task, was added. These tasks were also added when the SUD score remained high (Matthijssen et al., 2021). Once a memory was successfully processed, it was checked off on the case conceptualisation with the participant, and the therapy moved to the next traumatic event. Therapy was completed after all memories of case conceptualisation were processed. The treatment duration varied depending on the number of traumatic events and the time required for the processing of traumatic memories.

2.5. Statistical analyses

All analyses were conducted in R (R Core Team, 2023, version 4.3.2) and RStudio (Posit, 2024, version 2024.09.0). To determine the required sample size, we calculated the number of permutations for this non-concurrent multiple baseline between-subject design. For a robust randomisation test, the number of possible starting points (k) must exceed 20, ensuring 1/k (p < .05; Bulté & Onghena, 2009). With 11 participants and three starting points, our study yielded 177 randomisation possibilities, resulting in 1/177 (p < .001), ensuring sufficient statistical power. To assess the test-retest reliability within the baseline phase, the (Intraclass Correlation Coefficient; ICC; Koo & Li, 2016) using a one-way random effects model to measure consistency, was calculated for the BPI, TS-ID, and GAS.

To calculate the non-overlap of all pairs (NAP) for TS-ID, GAS, and BPI for each participant, the SingleCaseES package (Pustejovsky et al., 2024) was used. For the TS-ID and BPI, an improvement in symptoms was indicated by a decrease in scores, and for the GAS, an improvement was indicated by an increase. The baseline (phase A) was compared to the post-intervention and follow-up phases (phase B). Missing values were excluded from the analysis. The effect size was assessed based on the guidelines of Parker and Vannest (2009).

Group-level randomisation tests were performed for the TS-ID, GAS, and BPI (total and subscales) scores with the scan package (Wilbert & Luke, 2023) to compare the baseline (phase A) with the post-intervention and follow-up phases (phase B) using a t-statistic to measure phase differences. Randomisation tests were conducted using the distributions of the data based on random samples of n = 177 possible permutations. Missing values were interpolated prior to analysis.

PTSD symptom frequency scores (TS-ID) were plotted for visual analysis using the scplot package (Wilbert, 2023). PTSD diagnostic status (DITS-ID) was visually analysed using a table. The use of involuntary care was documented and described in the results section.

3. Results

Eleven participants engaged in an average of 13 therapy sessions (range = 9-16). On average, participants had experienced 12 traumatic and stressful events at the start of the study, and at the end of the study, ten participants had processed all of their traumatic and stressful events (SUD = 0). Table 1 provides a summary of the number of therapy sessions attended by each participant, along with the stressful and traumatic events treated during therapy. The ICC for the baseline TS-ID total frequency scores was .97, for the BPI total frequency scores .94, for the BPI total severity scores .95, and for the GAS scores .92, all indicating high reliability of the measurements (p < .01).

3.1. Primary outcome measures

3.1.1. PTSD symptoms

Figure 1 illustrate the visual analysis of PTSD symptom frequency scores (TS-ID) throughout the study. The NAP values of the TS-ID scores of individual participants indicated four participants with medium and seven participants with large differences between the A and B phases (see Table 4). The randomisation test showed a statistically significant group-level effect (observed Mdifference = 15.84, p < .01).

Figure 1.

Figure 1.

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Visual Analysis of TS-ID Frequency Scores.

Note. Participants are ordered according to the baseline lengths. A = baseline; I = intervention; B = post-intervention and follow-up.

Table 4.

NAP Values for TS-ID total frequency scores.

Participant NAP SE Effect size category
1 .92 .07 Medium
2 .79 .10 Medium
3 .87 .09 Medium
4 .99 .01 Large
5 1.00 .01 Large
6 .95 .05 Large
7 .84 .09 Medium
8 .98 .02 Large
9 1.00 .01 Large
10 1.00 .01 Large
11 1.00 .01 Large
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Note. NAP = non-overlap of all pairs; TS-ID = Trauma Screener Intellectual Disability; SE = standard error.

3.1.2. DSM-5-TR PTSD diagnostic status

Table 5 presents the DSM-5-TR PTSD diagnostic status per participants by different phases. Among the 11 participants, nine no longer met the diagnostic criteria for PTSD one week after the start of treatment. Participant 8 was reclassified as having PTSD at the first follow-up measurement, but this classification was no longer present at the second follow-up. In participants 2 and 5, the PTSD classification persisted throughout the study.

Table 5.

DSM-5-TR PTSD classification (DITS-ID).

Phase P1 P2 P3 P4 P5 P6 P7 P8 P9 P10 P11
Baseline start Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes
Baseline end Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes
Intervention No Yes No No Yes No No No No No No
Post-intervention No Yes No No Yes No No No No No No
Follow-up I No Yes No No yes No No Yes No No No
Follow-up II No Yes – No – No No No No No No
Follow-up III No Yes – No – No No No No No No
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Note. P = participant; baseline start = start baseline; baseline end = end baseline; intervention = after one week of treatment; post-intervention = three weeks after treatment; follow-up I = six weeks after intervention; follow-up II = nine weeks after intervention; follow-up III = four month after intervention.

3.1.3. Participants’ safety

One participant stayed in a crisis shelter during the baseline and intervention phases but actively participated in the therapy. After the intervention, he returned home. Crisis placement was considered unrelated to the intervention, as confirmed by both the participant and the professional caregiver. No other adverse events were reported in the participants’ electronic records.

3.2. Secondary outcome measures

3.2.1. Adaptive behaviour

The NAP values for the GAS scores indicated that the differences between A and B ranged from a weak effect to medium and one large effect (Table 6). The randomisation test was not statistically significant (observed Mdifference = 8.81, p = .712). Participant 1 was excluded from both analyses due to too many missing values (87%).

Table 6.

NAP Values for GAS and BPI scores.

Participant GAS Scaling scores BPI Total frequency score BPI Total severity score
NAP SE Effect size category NAP SE Effect size category NAP SE Effect size category
1 – – – .47 .19 Weak .42 .21 Weak
2 0.53 0.06 Weak .19 .13 Weak .25 .15 Weak
3 1.00 0.01 Large .58 .20 Weak .60 .19 Weak
4 0.57 0.08 Weak .60 .18 Weak .58 .18 Weak
5 0.92 0.05 Medium .70 .17 Medium .62 .20 Weak
6 0.62 0.06 Weak .87 .10 Medium .93 .06 Large
7 0.79 0.03 Medium .68 .15 Medium .68 .15 Medium
8 0.88 0.04 Medium .36 .18 Weak .38 .18 Weak
9 0.54 0.07 Weak .67 .20 Medium .60 .19 Weak
10 0.44 0.05 Weak .74 .13 Medium .66 .19 Medium
11 0.42 0.06 Weak .53 .21 Weak .58 .20 Weak
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Note. NAP = non-overlap of all pairs; GAS = Goal Attainment Scaling; SE = standard error; BPI = Brief Problem Inventory; NAP values for participant 1, GAS scores could not be calculated because too many values were missing (87%).

3.2.2. Behavioural problems

The NAP values for the BPI total frequency and severity scores indicate that the differences between A and B range from mainly weak effects to medium and (one) large effects (see Table 6). Randomisation tests were not statistically significant for the total frequency (observed Mdifference = 0.80, p = .407) and the total severity of behavioural problems (observed Mdifference = 0.73, p = .367).

3.2.3. Involuntary care

For one participant, one extra case of predetermined (multidisciplinary) involuntary care (off-label psychopharmacological medication) was recorded by professional caregivers of the participant during the intervention phase compared to the baseline. Another participant experienced one incident of involuntary care, recorded by the professional caregiver, during the follow-up phase. No other changes in recorded involuntary care measures or incidents of involuntary care were recorded.

4. Discussion

The results demonstrated a significant reduction in PTSD symptoms, with nine out of 11 participants no longer meeting the PTSD diagnostic criteria post-intervention. These improvements were maintained at both the 9-week and 4-month follow-ups, indicating the sustained efficacy of intensive EMDR therapy in this population. These findings align with previous research on intensive trauma therapy in children and adolescents with MID-BIF and PTSD (Ooms-Evers et al., 2021). Importantly, the intervention showed no adverse events, underscoring its safety.

Only one participant discontinued therapy. This is consistent with the low dropout rates consistently reported in intensive trauma-focused treatment programs (for example, Bongaerts et al., 2022; Voorendonk et al., 2023) in the general population. The intensive format, with frequent scheduled sessions has been found to be capable of reducing avoidance behaviour and fostering greater engagement (Hendriks et al., 2018; Szafranski et al., 2017).

The outcomes for adaptive behaviour indicated improvements in some participants, whereas others exhibited less noticeable changes. Meaningful changes in adaptive behaviour may require direct, targeted intervention aimed at learning new skills and adapting the environment. For example, adaptive behaviour, such as ‘the participant independently walking home from work’, may be facilitated by a reduction in PTSD symptoms, but the ongoing involvement of professional caregivers may result in the caregivers continuing walking alongside the individual, preventing actual improvement in adaptive behaviour in the participant.

Some participants showed minimal change in behavioural problems, whereas others showed weak improvement. In addition, no change (meaning no increase and no decrease) in involuntary care measures were observed, which could be attributed to the continued presence of behavioural problems. Although brief tracks of trauma-focused treatment have generally been found to reduce the severity of PTSD symptoms (Hoppen et al., 2023; Voorendonk et al., 2023), this may not necessarily translate into changes in behavioural problems (Cuijpers et al., 2020). Because the focus of EMDR therapy is on reducing PTSD symptoms by processing participants’ traumatic memories rather than targeting behavioural problems, the ability to directly address these problems may be limited. There is presently limited research on the association between behavioural problems and PTSD symptoms in individuals with MID-BIF. The current findings suggest that intensive trauma treatment is feasible and effective despite severe behavioural problems. Further research is needed to assess whether intensive trauma treatment may augment the effectiveness of interventions to reduce behavioural problems or vice versa. Alternatively, trauma treatment and behavioural interventions may reach their effects independently from each other and may enhance quality of life also independently.

4.1. Study limitations

First, although the randomised non-concurrent multiple baseline design offers robust insights, it does not provide information on which subgroups within the MID-BIF population benefit more or less from the intervention. Second, the PTSD classification was not measured repeatedly across the different study phases, which prevented us from measuring a statistically significant loss of PTSD diagnostic status. A third limitation is the potential selection bias due to loss to follow-up measurements. The design used in the current study does not account for this bias, as not all participants were included in the analyses, which may have affected the validity and generalisability of the results. Fourth, we investigated a specific sample of adults with MID-BIF, all living in supported housing in one Dutch ID care service. Further research is needed to determine whether the observed effects can be replicated in more diverse or larger samples, which would enhance the applicability of these treatment approaches across various clinical contexts.

5. Conclusion

In conclusion, the results of this study support the efficacy and safety of intensive EMDR therapy using a rotating team of therapists to reduce PTSD symptoms among adults with MID-BIF and behavioural problems. Although the treatment demonstrated significant improvements in PTSD symptoms, the effects on adaptive behaviour and behavioural problems were more variable, suggesting the need for further research to explore complementary approaches. Despite the small sample size, our results provide valuable insights and clinical implications for offering accessible trauma therapy to this populationimplicating that severe behavioural problems may not necessarily be a contraindication for intensive trauma treatment in individuals with MID-BIF.

Funding Statement

This work was supported by ZonMw, Netherlands Organization for Health Research and Development and Scientific Research Foundation ‘s Heeren Loo.

Disclosure statement

No potential conflict of interest was reported by the authors.

Data availability statement

Data that support the findings of this study are available on request from the corresponding author. The data are not publicly available due to privacy or ethical restrictions.

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Associated Data

This section collects any data citations, data availability statements, or supplementary materials included in this article.

Data Availability Statement

Data that support the findings of this study are available on request from the corresponding author. The data are not publicly available due to privacy or ethical restrictions.

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