Effectiveness of an intensive outpatient treatment programme combining prolonged exposure and EMDR therapy for adolescents and young adults with PTSD in a naturalistic setting

ABSTRACT

Background: Psychotherapeutic interventions aimed at treating posttraumatic stress disorder (PTSD) in adolescents and young adults are hampered by high dropout rates. Looking at the results from adult treatments, short, intensive, outpatient treatment programmes may offer a promising alternative, but it has yet to be tested in this young population.

Objective: To assess the results of a six-day intensive outpatient trauma-focused treatment programme for young individuals (12-25 years) with PTSD. The treatment combined prolonged exposure and EMDR therapy, supplemented with physical activity and the participation of relatives and/or friends. Treatment was performed by a rotating team of therapists.

Methods: Seventy-four adolescents and young adults (89% women, mean age = 18.6 years, 36 patients aged 12–17 and 38 patients aged 18-25; SD = 3.1) with PTSD and a minimum of four memories of A-criterion traumatic events participated in the programme. PTSD symptoms, depressive symptoms, and the perceived burden of trauma symptoms were assessed before treatment, at the start and one month after treatment.

Results: Patients showed a significant reduction in PTSD symptoms from pre-treatment to one month after treatment (Cohen’s d = 1.66). Of all patients, 52 (70%) showed a clinically meaningful response, and 48 (65%) no longer met the diagnostic criteria for PTSD one month after treatment. Depressive symptoms also decreased significantly (Cohen’s d = 1.02). The dropout rate was 4% (N = 3). None of the patients experienced an adverse event or worsening of symptoms.

Conclusions: Results suggest that a short, intensive, outpatient therapy programme combining prolonged exposure, EMDR therapy, physical activity, and participation of relatives and friends, is well-tolerated, and an effective and safe treatment alternative for adolescents and young adults with PTSD due to multiple traumatization.

Highlights

• An intensive trauma-focused treatment programme, in an outpatient format has proven effective for adolescents and young adults.

• 65% of the participants lost their PTSD diagnosis following six treatment days.

• Only 4% of patients dropped out and no adverse events occurred.

Introduction

Trauma-focused cognitive behavioral therapy and eye movement desensitization and reprocessing (EMDR) therapy are first-choice interventions for adolescents and (young) adults with post-traumatic stress disorder (PTSD) according to current international treatment guidelines (International Society for Traumatic Stress Studies [ISTSS]; Bisson et al., 2019; National Institute for Health and Care Excellence [NICE], 2018). These treatments are typically offered at a frequency of one treatment session per week and show good results regarding the reduction of PTSD in adolescents and (young) adults (John-Baptiste Bastien et al., 2020; Mavranezouli et al., 2020).

Although effective, these treatments are associated with relatively high dropout rates in adults (18%−36%; Imel et al., 2013; Lewis et al., 2020), adolescents, and young adults (Simmons et al., 2021). A meta-analysis of 42 studies on PTSD treatment in adults found that the more weekly sessions patients received, the more patients dropped out of the treatment (Imel et al., 2013). As there is also evidence to suggest that the more frequent the sessions, the better the treatment outcomes (Gutner et al., 2016), it may be helpful to deliver treatment sessions at a higher session frequency over a short period of time to reduce dropout rates. Similarly, treatment programmes for adults that use a higher session frequency over a short period have been found to yield relatively low dropout rates (<10%) and equally effective outcomes compared to therapies delivered in a weekly session format (Ragsdale et al., 2020; Van Woudenberg et al., 2018). A systematic review of 11 studies examining intensive outpatient programmes for PTSD in adults found a pooled dropout rate of 5.5% (Sciarrino et al., 2020), which is substantially lower than the 18-36% dropout in weekly offered treatments (Imel et al., 2013; Lewis et al., 2020; Simmons et al., 2021).

Despite the efforts to reduce the dropout rate, another challenge remains. Not every patient benefits from current trauma interventions. To further enhance the effectiveness of treatment and retention, a growing number of adult intensive treatment programmes combine prolonged exposure (PE) therapy and EMDR therapy, sometimes complemented by physical activity and psychoeducation (Auren et al., 2022; Matthijssen et al., 2024; Van Woudenberg et al., 2018). Prolonged exposure involves continuous controlled exposure to traumatic memories to reach extinction through the disconfirmation of harm expectancy, based on the inhibitory learning theory (Craske et al., 2014; Foa et al., 2007). On the other hand, EMDR therapy facilitates the processing of traumatic memories by taxing patients’ working memory, which reduces the emotional intensity of memories (De Jongh et al., 2024). Combining these evidenced-based therapeutic approaches could possibly improve the results of trauma-focused therapy due to their complementary working mechanisms (Van Minnen et al., 2020). Furthermore, a meta-analysis found that adding physical activity improves the effect of PTSD treatment (Rosenbaum et al., 2015). Such combined treatment programmes for adults typically apply a therapist rotation model, in which each session is delivered by a different therapist. Evidence suggests that rotation improves the treatment adherence of therapists and is likely to decrease therapists’ fear and avoidance behaviour (Van Minnen et al., 2018).

Although promising in adults (Matthijssen et al., 2024; Van Woudenberg et al., 2018), conclusive evidence for the efficacy of such combined programmes in adolescents is lacking. To the best of our knowledge, only one study has explored the effectiveness of an intensive programme combining prolonged exposure, EMDR therapy, physical activity, and psychoeducation provided by rotating therapists for an adolescent population (Van Pelt et al., 2021). The results of this study, conducted in an inpatient setting, showed that, after an average of 13 treatment days, 63% of the 27 adolescents reached diagnostic remission of PTSD (Cohen’s d = 1.39), while no dropout occurred. Based on our search of databases such as PubMed, PsycINFO, Google Scholar, and ScienceDirect, we could not detect any studies evaluating intensive treatment programmes combining evidenced-based therapies for adolescents in an outpatient setting. The present study elaborated on the outpatient programme for adults developed by Matthijssen and colleagues (2024). It combines prolonged exposure and EMDR therapy, supplemented by physical activity and involvement of the patient’s network, such as relatives and friends, using a therapist’s rotation model. In our clinical experience, we observed that relatives play a positive role in providing support and motivation to patients.

The purpose of the present study was to determine the effectiveness and dropout rate of an intensive outpatient programme for adolescents and young adults with PTSD due to multiple traumatization. We hypothesised that treatment would be associated with significant reductions in (1) severity of PTSD symptoms, (2) number of patients meeting the diagnostic criteria for PTSD, (3) perceived burden of trauma symptoms experienced in various areas of life, and (4) severity of depressive symptoms. In addition, we hypothesised that the intervention would be associated with a low dropout rate (<10%) and that no adverse events would occur.

Method

Participants

Participants were referred to the outpatient intensive trauma treatment programme at GGZ Noord-Holland-Noord, a mental health care organisation in the Netherlands, specializing in services for children, adolescents, and (young) adults to deal with a range of mental health issues. Of 80 consecutive referrals eligible to participate, 77 agreed to participate and 74 consented to the use of their data for our study. Accordingly, the sample included 74 individuals aged 12–25 years (mean age = 18.6 years; 36 patients aged 12–17 and 38 patients aged 18-25; SD = 3.1). Participants were eligible if they had been exposed to four distinct traumatic events that met the A criterion for PTSD in their past. These events could involve different perpetrators, different types of trauma or different types of A-criterion-qualifying events involving the same perpetrator. Establishing four traumatic events as eligibility criteria helped ensure that the programme focused on individuals who were likely to have more severe and comorbid symptoms. To this end, this may help enhance the generalisability to a broader population of patients who suffer from severe and complex PTSD due to complex trauma histories. They also had to meet the diagnostic criteria for PTSD according to the Diagnostic and Statistical Manual of Mental Disorders, 5th Edition (DSM; American Psychiatric Association, 2013). The patients were treated between March 2021 and January 2023.

Procedure

The evaluation of the treatment programme was performed in accordance with the regulations for research as stated in the Declaration of Helsinki and the Dutch Medical Research on Humans Act (World Medical Association, 2001) concerning scientific research. The Medical Research Involving Human Subjects Act (WMO) does not apply, since routine outcome monitoring data of the treatment programme were used for analysis, no random allocation took place, and no additional infringement of the individual was expected. Only patients who met inclusion criteria and provided written permission (and parents as well if necessary) for the anonymous use of their data were included in data analyses.

Patients were referred by their therapist or general practitioner from various regions of the Netherlands. After referral, independent assessors checked the inclusion criteria using the Life Events Checklist for DSM-5 (LEC-5; Boeschoten et al., 2014) and the Clinician-Administered PTSD Scale for DSM-5 (CAPS-5; Boeschoten et al., 2018). Comorbid diagnoses were acquired from the referrer by requesting them to document the patient’s current comorbid diagnoses in the referral letter. Patients completed two self-report questionnaires: Children’s Revised Impact of Event Scale (CRIES-13; Verlinden & Lindauer, 2017) and Beck Depression Inventory (BDI-II; Beck et al., 1996). They also completed six additional items regarding the perceived burden of trauma symptoms in various areas of life. No other trauma treatments were provided after inclusion and first assessment. The referrer stayed involved to support the patient and, if necessary, to continue treatment after the intensive trauma treatment programme. After this assessment, a treatment plan was collaboratively drawn up with the patient, referrer, and patient’s relatives. The trauma history of the patient was used to create a case conceptualisation with memories written in sequence, starting with the most disturbing memory. The self-report questionnaires were administered again at the start of the first day of treatment and one month after the end of treatment. One month after treatment, the CAPS-5 was conducted again by independent assessors. Possible adverse events, such as suicide attempts and serious self-harm, were monitored by therapists from the first assessment until one month after treatment. Five weeks after treatment completion, a treatment evaluation meeting was conducted with the patient, relatives, referrers, and therapists.

Treatment

The intensive trauma treatment program consisted of six treatment days, divided into three treatment days per week, for two consecutive weeks. Each day was structured in the same way to facilitate the processing of traumatic memories using both Prolonged Exposure (PE) and EMDR therapy. At least one traumatic memory was addressed each day, starting with PE, followed by EMDR therapy on the same memory after a short break

Daily Structure:

1. 90 min of Prolonged Exposure (PE).

2. 15-minute break.

3. 90 min of EMDR-therapy.

4. Short meeting with patient and their relatives.

5. Lunch with patient and relatives.

6. Physical activity was guided by a (psychomotor) therapist who led different types of sports.

Even if the memory was not fully processed by the end of the day, the next day, the next traumatic memory on the treatment schedule was the focus of treatment the next day. Therapists rotated daily, resulting in patients receiving treatment from to 3–5 therapists. At the end of each treatment day, the therapists reported the progress in the patient’s treatment file. All therapists had a Master’s degree in clinical psychology and were trained in prolonged exposure and EMDR therapy. Therapists were instructed to follow the printed protocols precisely when performing the therapies. The sessions were supervised at times to prevent protocol drift. In addition, supervisors attended weekly multidisciplinary meetings to ensure adherence to protocols. The patients’ relatives attended one or two meetings each week with a family therapist. To increase understanding and support from relatives of the patient the family therapist offered support to relatives and provided psychoeducation about PTSD and the treatment programme.

Exposure

The Dutch protocol of Van Minnen and Arntz (2017), based on Foa et al. (2007), was used for prolonged exposure. Patients were exposed to a traumatic memory by imagining the trauma as vividly as possible, while describing sensory details in the present tense and in the first pronoun, aloud, with eyes closed, for 90 minutes per session. The hotspots (the most distressing parts of the traumatic memory) were repeated several times during the session. Where helpful, in vivo material collected by therapists and patients based on the case conceptualisation was used to cue trauma memories and facilitate deepened extinction. This technique involves combining multiple fear-provoking stimuli to enhance inhibitory learning and improve its long-term retrieval (Craske et al., 2014). Owing to the intensity of the programme, patients did not receive homework, although they were encouraged to practice with in vivo material.

EMDR therapy

EMDR therapy was performed according to the EMDR standard protocol (De Jongh & Ten Broeke, 2019) for patients aged 18 years and older or the EMDR standard protocol for children and adolescents up to 18 years of age (De Roos et al., 2020) for 90 min per session. In the case of anticipatory fear and avoidance behaviour, patients’ most horrible fantasies about the future were desensitised using the ‘flashforward protocol’ (Logie & De Jongh, 2014). Different and varied tasks were used to maximize the taxation of patients’ working memory, such as eye movements, cognitive tasks, cycling on a home trainer and boxing, while recalling the traumatic memory, according to EMDR 2.0 (see Matthijssen et al., 2021). During EMDR therapy, cognitive interweaves (Shapiro, 2007) were used when deemed necessary.

Materials

CAPS-5 NL

The primary outcome measures were (1) meeting criteria for a PTSD diagnosis and (2) the severity of PTSD symptoms. Both were measured using the Dutch version of the CAPS-5 for the DSM-5 (Boeschoten et al., 2018). The CAPS-5 NL has good psychometric properties (Cronbach’s α: 0.62–0.83 [Cronbach’s α: .75 in our sample], ICC for inter-rater reliability: 0.97– 0.99) (Boeschoten et al., 2018). Each of the 20 DSM-5 criteria are rated on a severity scale (0-4) for occurrence in the past month. The total score can sum up to 80. A severity score ≥2 on an item indicates that a particular PTSD criterion, according to the DSM-5, is met.

CRIES-13

The CRIES-13 (Verlinden & Lindauer, 2017) is a self-report questionnaire and consists of 13 questions screening PTSD symptoms. Each item is rated on a 4-point scale: 0 (absent), 1 (rarely), 3 (sometimes), and 5 (often), resulting in a maximum total score of 65. The CRIES is considered reliable, valid, and has high internal consistency (Cronbach’s alpha: 0.9; [Cronbach’s of the sample was 0.7], Verlinden et al., 2014).

BDI-II

The severity of depressive symptoms was assessed using the Beck Depression Inventory (BDI-II) (Beck et al., 1996). This self-report questionnaire consists of 21 items. Each item is rated on a 4-point scale (range 0-3). The total score can sum up to 63. The BDI-II is considered reliable, valid, and has high internal consistency (Cronbach’s alpha: 0.9; [Cronbach’s α was 0.9 in our sample], Wang & Gorenstein, 2013).

Items to index the perceived burden of PTSD symptoms on daily life

Matthijssen et al. (2024) formulated a separate item to assess the effect of trauma symptoms in daily life using the question: ‘To what extent do you currently experience problems in your daily life due to your trauma symptoms?’. For the current treatment programme, we adopted this item using a response scale ranging from 0 (‘none’) to 10 (‘maximum’) (half marks possible), and added five other items to index patients’ perceived burden of trauma symptoms on various areas of daily life that were formulated in the following way: ‘To what extent do your trauma symptoms currently hinder you in the area of (I) school/study/work, II) functioning at home, (III) friends/relationships, (IV) social time and (V) sexuality?’ For these items, patients were asked to indicate on a scale of 0–10 the extent to which they were hindered by their trauma symptoms (0 = ‘no hinder’, 10 = ‘maximum hinder’).

Data analyses

Data analyses were performed using IBM SPSS version 27. All data were screened for data-entry errors and outliers and the extent of missing data was assessed. Expectation maximisation (EM) algorithm imputation was performed for missing data in the self-report questionnaires and the separate items indexing the effects of patients’ trauma symptoms in daily life. This algorithm generates values while preserving the relationship between one variable and other variables. Less than five percent of the self-report data and separate items were missing. Analyses using the data with and without imputations did not show meaningful changes in the descriptive statistics across measurement moments. Four patients had one or two CAPS-5 NL measurements missing and were therefore, removed from the analysis. Next, the normality assumptions were checked. Characteristics were described by calculating frequency distributions for demographic and baseline clinical variables and by calculating means and standard deviations. To determine whether patients experienced reliable symptom improvement on CAPS-5, a reliable change index (RCI) was calculated according to the formula of Jacobson and Truax (1991). The standard deviation and Cronbach’s α (internal consistency) of the pretreatment CAPS-5 data were used to determine the RCI for this sample. Paired sample t-tests were conducted to assess differences in total scores of the CAPS-5, CRIES-13, BDI-II, and additional items between pretreatment and post-treatment. Additionally, a paired sample t-test was used to analyse differences in total scores of the CRIES-13, BDI-II, and additional items between pretreatment and directly prior to the first session on the first treatment day to assess any differences between these measurement points. To further explore the CAPS-5 results, exploratory analyses were performed on the total severity scores of the different CAPS-5 domains using paired sample t-tests. Within-subject effect sizes were calculated using Cohen’s d.

Results

Sample characteristics

Table 1 shows the sample characteristics of the 74 consecutive participants. Three patients (4%) dropped out prematurely because of COVID-19 (N = 1) or unwillingness to continue (N = 2).

Table 1.

Characteristics of the treatment sample (N = 74).

Variable	%	N
Gender
Female	79.7	59
Male	10.8	8
Other	9.5	7
Previous trauma treatment	42	31
Traumatic events
Sexual abuse	83.8	62
Physical abuse	100	74
Traumatic loss	33.8	25
Accidents, disasters	58.1	43
Comorbid disorders	80	59
Mood disorder	44.6	33
Developmental disorder	25.7	19
Personality disorder	17.6	13
Anxiety disorder	12.2	9
Eating disorder	10.8	8
Somatic symptom disorder	8.1	6

Note. The gender group ‘other’ consists of all born females identifying as males.

Treatment outcomes

CAPS-5

The mean CAPS-5 total scores at pre-treatment and one month after treatment are shown in Table 2 and Figure 1. These results showed a significant decrease in PTSD symptom severity over time, with a large effect size (t(69) = 13.85, p < .001; Cohen’s d = 1.66). All CAPS-5 domains showed significant reductions from screening to the month follow-up regarding the severity of intrusions (t(1, 69) = 13.01, p < .001; Cohen’s d = 1.56), avoidance (t(1, 69) = 12.62, p < .001; Cohen’s d = 1.51), negative alterations in cognition and mood (t(1, 69) = 12.19, p < .001; Cohen’s d = 1.46), and alterations in arousal and reactivity (t(1, 69) = 9.38, p < .001; Cohen’s d = 1.12). The internal consistency of the pre-treatment CAPS-5 total score proved acceptable (Cronbach’s α = .75), and the reliable change index (RCI) was 14.32. More than 70% of the patients (N = 52) showed significant reliable symptom improvement from pre-treatment to one month after treatment and none of the patients showed symptom worsening. Of all patients, 65% (N = 48) no longer fulfilled the diagnostic criteria for PTSD one month after the conclusion of treatment.

Table 2.

PTSD symptoms, depressive symptoms and burden of trauma from PTSD symptoms at pre-treatment, prior to the first day of treatment and one month after treatment.

	N	Pre-treatment	Prior to the first day of treatment	One month after treatment	Effect size Pre-treatment  – One month after treatment
		M (SD)	M (SD)	M (SD)	Cohen’s d
CAPS-5 NL	70	47.37 (10.57)	-	21.79 (16.61)	1.66*
CRIES-13	74	53.23 (7.54)	54.22 (8.68)	29.13 (18.56)	1.42*
BDI-II	74	36.10 (11.32)	35.74 (12.48)	22.40 (17.15)	1.02*
Additional items
Total burden	74	7.55 (1.65)	7.80 (1.64)	3.53 (3.08)	1.35*
Study / work	74	7.61 (2.28)	7.38 (2.61)	3.64 (3.19)	1.11*
Home	74	6.74 (2.26)	6.77 (2.29)	3.49 (2.98)	.91*
Friends	74	6.92 (2.08)	6.91 (2.57)	3.62 (3.30)	1.06*
Social time	74	6.39 (2.41)	6.82 (2.28)	3.30 (3.09)	.96*
Sexuality	74	5.63 (3.55)	6.15 (3.89)	3.62 (3.54)	.55*

Note. The scale of the questions ranged from 0 (no burden) to 10 (maximum burden).

*p < .001.

Figure 1.

Total mean CAPS-5 scores (N = 70) with 95% intervals at pre-treatment and one month after treatment.

Self-report questionnaires

All mean total scores at pretreatment and at one month after treatment are shown in Table 2. Self-reported PTSD symptom severity and depressive symptom severity both showed a significant decrease from pre-treatment to one month after treatment, with a large effect size (t(74) = 12.25, p < .001; Cohen’s d = 1.42). Analyses showed no significant decrease from pretreatment to the first day of treatment for PTSD symptom severity (t(73) = −1.42, p = .16) or depressive symptom severity (t(73) = .36, p < .72). In addition, the perceived burden of PTSD symptoms in various areas of life decreased significantly from pretreatment to one month after treatment. There were no significant decreases in any of these outcomes from pretreatment to the first day of treatment.

Adverse effects

According to the therapists’ reports, none of the patients showed an increase in risky behaviour such as self-harm or suicide attempts, and none of them showed symptom worsening.

Discussion

To the best of our knowledge, this is the first study to evaluate the effectiveness of an intensive six-day outpatient trauma treatment programme for adolescents and young adults, combining prolonged exposure and EMDR therapy delivered by rotating therapists. Our results show that 70% of the patients with PTSD due to multiple traumatisation had clinically meaningful improvement and 65% of patients no longer met the diagnostic criteria of PTSD one month after treatment.

Our findings are consistent with Emotional Processing Theory (EPT) by Dancu and Foa (1992, 2007) and the theoretical underpinnings of EMDR therapy (Shapiro, 2018). EPT suggests that successful treatment requires activating the fear structure and integrating corrective information. Conversely, EMDR therapy, grounded in the Adaptive Information Processing (AIP) model, posits that PTSD symptoms result from inadequately processed and maladaptively stored traumatic memories. EMDR aims to transform distressing memories by facilitating the brain’s natural processing. While the data appear to support both theoretical frameworks, further specificity is required to clarify how the findings support these models. In addition, as the two interventions were both offered in one program, it is difficult to tease out which specific procedures contributed to the observed effects and by what mechanisms these effects were achieved.

Additionally, our findings align with studies on the effectiveness of other intensive treatment programmes for adults, both in  – and outpatient, combining two evidence-based therapies with a therapist rotation model (Auren et al., 2022; Matthijssen et al., 2024; Van Woudenberg et al., 2018). The results of our outpatient programme also support finding from an inpatient programme for adolescents combining two evidence-based therapies offered by rotating therapists (Van Pelt et al., 2021). Overall, our results support the notion that an outpatient intensive trauma treatment programme can be effective in treating PTSD in adolescents and young adults.

In our treatment sample, patients reported less burden of PTSD-symptoms on various areas of their lives; similar to findings in adult interventions (Auren et al., 2022; Matthijssen et al., 2024). Additionally, consistent with studies in both adult and adolescent populations, comorbid depressive symptoms decreased significantly (Auren et al., 2022; Hendriks et al., 2017; Matthijssen et al., 2024).

In addition to faster recovery from PTSD symptoms, an important reason for offering trauma treatment in an intensive programme, is to reduce dropout. The dropout rate in our study was 4% (comparable to the average 5.5% dropout rates reported in similar intensive adult protocols; Sciarrino et al., 2020), which is substantially lower than the average 18-36% dropout in regular, weekly offered treatments (Imel et al., 2013; Lewis et al., 2020; Simmons et al., 2021). Conceivably, the low dropout rate in our intensive treatment programme is due to the high frequency of sessions in a short period of time (Ragsdale et al., 2020; Sciarrino et al., 2020) and the clear endpoint of the treatment after six days.

We observed no adverse events or significant symptom worsening during treatment from the first treatment day to the last follow-up, which is consistent with previous studies (Hendriks et al., 2017; Van Pelt et al., 2021). The low dropout rate, together with the absence of any adverse event or symptom worsening, suggests that adolescents and young adults can tolerate the high frequency of treatment sessions delivered by rotating therapists in an outpatient setting.

The findings of this study and other studies using a therapist rotation model support the notion that it is not always necessary to have a one-on-one, long-lasting therapeutic alliance. In our clinical practice, we observed that it is not necessary for different therapists and patients to invest time in building such an alliance, at least if the therapist acts competently. Therapists begin prolonged exposure five minutes after meeting the patient. It has been argued that this is possible because patients develop a therapeutic alliance with the programme and the team as a whole, based on their confidence in the efficacy of the programme, rather than with the therapist per se. See Van Minnen et al. (2018) for discussion and evidence suggesting that the rotation of therapists improves their treatment adherence and decreases their fear and avoidance behaviour.

The findings of this study should be interpreted in light of several limitations. First, the absence of a control condition limits direct comparison with independent group-based studies. However, our findings can still be contextualised within the broader literature on intensive trauma-focused interventions. While our study relied on pre  – and post-treatment comparisons to show significant improvements, the large effect sizes and substantial symptom improvement indicate that our outpatient intensive therapy effectively reduced PTSD and depressive symptoms. Furthermore, no additional trauma treatment was offered from referral to one-month post-treatment. Therefore, it seems unlikely that time or other nonspecific factors (fully) account for our findings. Additionally, high internal consistency and a significantly reliable change index support the robustness of the findings. The majority of patients no longer met the PTSD diagnostic criteria one-month post-treatment, aligning with the controlled study outcomes, suggesting that our approach holds considerable promise. Second, we cannot rule out that the symptoms may worsen after one month of treatment. Nevertheless, other studies on PTSD symptoms in adolescents and adults have shown that treatment effects remain stable over time (Matthijssen et al., 2024; Van Pelt et al., 2021). Third, the majority of the study sample was born female (89.1%), which may hamper generalisability beyond female-sex individuals. However, several studies have shown comparable trauma treatment outcomes between males and females (Danzi & La Greca, 2021; De Roos et al., 2021). Finally, independent assessors were not blinded to the time point of patient assessment, which may have led to a positive rating bias for assessments after treatment completion.

An important strength of this study was the relatively large sample of adolescents and young adults exposed to a wide variety of traumatic events and with high rates of comorbidity, which enhanced the external validity of the results. Another strength was the use of both standardised self-report questionnaires and a reliable and valid clinician-administered interview (CAPS-5) to assess the effectiveness. Additional strengths included the use of written protocols and the presence of supervisors at multidisciplinary meetings to optimise treatment fidelity.

Future studies should provide a better understanding of the factors contributing to treatment success. A small subsample of patients (N = 18) in our study failed to show a clinically meaningful decrease in symptoms. It is unclear which factors contribute to this lack of treatment response. Potential (severe) comorbidity, varying motivation, and potential anxiety caused by the idea of losing PTSD symptoms may have contributed to a lack of treatment success and need to be explored in future research.

Although the programmes combining two evidence-based therapies emerged from the hypothesis that the different working mechanisms may enhance each other (Van Minnen et al., 2020), this hypothesis needs to be further explored. Our study was not designed to examine the individual contributions of different treatment components to changes in symptoms. In future research a comparison between an intensive treatment programme using one evidence-based therapy and a therapy combined programme is recommended to distinguish the specific contributions of the different treatment components. Additionally, to compare the effectiveness of either an intensive programme or a treatment delivered in a less frequent format, a randomised controlled trial is required.

In conclusion, the present results show that an intensive six-day outpatient trauma treatment programme combining prolonged exposure, EMDR therapy, physical activity, and network participation can be effective and safe for adolescents and young adults with PTSD due to multiple traumatisation. For adolescents and young adults with PTSD, the opportunity to participate in a treatment programme with a high retention rate and rapid recovery can be invaluable at a time in their lives when they should be achieving major developmental goals.

Disclosure statement

Suzy Matthijssen receives income for the training of postdoctoral professionals in EMDR 2.0 and teaching about trauma related disorders and (intensive) trauma treatment. Ad de Jongh receives income for training of postdoctoral professionals in EMDR, EMDR 2.0 and teaching about trauma related disorders and (intensive) trauma treatment. The other authors have no conflict of interest to disclosure.

Data availability statement

The data that support the findings of this study are available from the corresponding author upon reasonable request.