Exploring the feasibility and acceptance of huddinge online prolonged exposure therapy (HOPE) for severe and complex PTSD

ABSTRACT

Background: Trauma-focused cognitive behavioural therapy such as prolonged exposure is considered firsthand choice for treatment of posttraumatic stress disorder (PTSD) but is seldom available in regular care. Digital therapy is proposed to bridge this gap, but its effectiveness for severe and complex PTSD is uncertain. The primary objective of the current study was to examine the feasibility, acceptability, and preliminary effects of digital therapist-guided prolonged exposure (Huddinge Online Prolonged Exposure; HOPE).

Method: Thirty participants with moderate to severe PTSD, with the majority self-reporting complex PTSD symptoms, received HOPE over a ten-week period. Eighty percent of participants had been diagnosed with other psychiatric comorbidity by a mental health professional. Primary outcome was the feasibility and acceptability of treatment. Participants were repeatedly assessed using clinician- and self-rated outcome measures at baseline, during the treatment period, post-treatment, and at 1-month and 6-month follow-ups to estimate preliminary treatment effects. The Clinician Administered PTSD Scale version 5 (CAPS-5), administered by independent assessors, evaluated PTSD symptom severity.

Results: HOPE proved feasible and effective, delivering evidence-based treatment content in a psychiatric outpatient setting with reduced therapist time. The treatment was well-tolerated, with no severe adverse events and a 17% dropout rate. Sixty-four percent completed the exposure-based portion of the treatment, and overall satisfaction measured by the Client Satisfaction Questionnaire was moderate. Furthermore, significant reductions in PTSD symptoms as assessed with the CAPS-5 (Cohen's d = 1.30 [95% CI −1.79 to −0.82]) at the primary endpoint 1 month which were sustained at the 6-month follow up.

Conclusion: Altogether, this study indicate feasibility of treating severe and complex PTSD through a digital PE intervention, thereby building upon and extending previous research findings. Large-scale controlled trials are needed to further validate the specific effect and long-term benefits of HOPE.

Trial registration: ClinicalTrials.gov identifier: NCT05560854.

HIGHLIGHTS

• HOPE, a digital therapist-guided prolonged exposure programme, demonstrated feasibility and preliminary effects for severe and complex PTSD in a psychiatric outpatient setting, while requiring less therapist time.

• HOPE was well-tolerated by participants, with a relatively low dropout rate and average overall satisfaction.

• Significant reductions in PTSD symptoms were observed, and these benefits were sustained at the 6-month follow-up.

Antecedentes: La terapia cognitivo conductual centrada en el trauma como la exposición prolongada se considera una opción de primera mano para el tratamiento del trastorno de estrés postraumático (TEPT), pero rara vez esta disponible en la atención habitual. Se propone la terapia digital para cerrar esta brecha, pero su efectividad para el TEPT complejo y grave es incierta. El objetivo primario del presente estudio fue examinar la viabilidad, aceptabilidad y efectos preliminares de la exposición prolongada guiada por un terapeuta digital (Exposición Prolongada En línea de Huddinge; HOPE por sus siglas en ingles).

Método: Treinta participantes con TEPT moderado a severo, la mayoría de los cuales auto reportaron síntomas de TEPT complejo, recibieron HOPE durante un período de diez semanas. El ochenta por ciento de los participantes había sido diagnosticado con otra comorbilidad psiquiátrica por un profesional de salud mental. El resultado primario fue la viabilidad y aceptabilidad del tratamiento. Los participantes fueron evaluados repetidamente utilizando las medidas de resultado auto-evaluadas y evaluadas por el clínico al inicio del estudio, durante el período de tratamiento, el post-tratamiento y al mes y seis meses de seguimiento para estimar los efectos preliminares del tratamiento. La escala de TEPT administrada por el clínico versión 5 (CAPS-5), administrada por evaluadores independientes, evaluaron la gravedad de los síntomas de TEPT.

Resultados: HOPE demostró ser factible y efectiva, brindando contenido de tratamiento basado en la evidencia en un contexto de pacientes ambulatorios con un tiempo reducido del terapeuta. El tratamiento fue bien tolerado, sin eventos adversos serios y con una tasa de abandono del 17%. El sesenta y cuatro por ciento completo la porción del tratamiento basado en la exposición, y la satisfacción general medida por el Cuestionario de Satisfacción del Cliente fue moderada. Además, se observaron disminuciones significativas de los síntomas de TEPT evaluados con el CAPS-5 (d de Cohen = 1.30 [IC 95% −1.79 a −0.82]) en el criterio de valoración principal al mes, que se mantuvieron a los 6 meses de seguimiento.

Conclusiones: En conjunto, este estudio indica la viabilidad de tratar TEPT complejo y grave a través de una intervención de EP digital, aprovechando y ampliando así los hallazgos de investigaciones previas. Se necesitan estudios controlados a gran escala para validar aún más el efecto específico y los beneficios a largo plazo de HOPE.

KEYWORDS:

• Post-traumatic stress disorder; complex post-traumatic stress disorder; prolonged exposure; guided internet delivered treatment
• digital treatment
• trauma focused cognitive behaviour therapy

PALABRAS CLAVE:

• Trastorno de estrés postraumático
• trastorno de estrés postraumático complejo
• exposición prolongada
• tratamiento guiado entregado por internet
• tratamiento digital
• terapia cognitive conductual centrada en el trauma

1. Introduction

Trauma is a global public health concern affecting 70% of the world's population. PTSD, with a life time prevalence of approximately 5.6% (Koenen et al., 2017), leads to debilitating symptoms and comorbidities, including substance use and suicidal thoughts, imposing a significant societal and personal burden (Kessler et al., 2012; Kessler et al., 1995; McFarlane et al., 1994; Song et al., 2018). Untreated, PTSD often becomes a chronic condition (Morina et al., 2014; Steinert et al., 2015).

Fortunately, trauma-focused psychological therapies, such as trauma-focused cognitive behavioural therapy (CBT-T) protocols have a solid evidence-base in the treatment of PTSD (Hamblen et al., 2019). However, there is a discrepancy between demand and availability of evidence-based treatments for PTSD. Approximately half of individuals with PTSD actively seek help for their condition (Kessler, 2000) and barriers to seeking help include perceived stigma associated with attending treatment, low ability to understand and utilise medical information, insufficient awareness and uncertainty about treatment options and effects, fear of increasing symptoms of PTSD and financial reasons (Kantor et al., 2017). In addition, the standard delivery of trauma-focused treatment involves weekly, in-person sessions over several months, which may pose challenges for certain individuals to access due to work responsibilities, travel, and childcare requirements (Davis et al., 2008; Kantor et al., 2017). Furthermore, the availability of evidence-based treatment for PTSD even for those who seek help remains alarmingly scarce (e.g. Deacon & Farrell, 2013; Maguen et al., 2018; Zayfert et al., 2005). Recent data from WHO's World Mental Health Surveys highlight a concerning gap in the treatment of PTSD worldwide, with only 17% diagnosed with PTSD receiving evidence-based psychological treatment (Stein et al., 2023). The combination of a growing need for treatment and a lack of access to evidence-based treatment poses a significant public health challenge, and it is evident that measures are necessary to enhance accessibility.

Implementing remotely delivered digital treatment presents a promising way of substantially enhancing access to treatment and may come with several advantages over traditional psychological treatments. Firstly, internet-based treatment could potentially lower the threshold for seeking help by reducing patients’ concerns about stigma compared to visiting regular health care services in person (Bragesjö et al., 2021). Further, it is highly accessible and convenient in the sense that it may be easier to fit it around work or school commitments. The need for traveling to appointments is eliminated and geographical barriers between therapists and patients can be overcome. The therapist time per patient could be reduced making this treatment most likely more cost-effective than face-to-face treatment. The provision of standardised treatment and possible reduced emotional involvement may also enhance treatment adherence in the therapists. Guided internet-delivered cognitive–behavioural therapy holds support for numerous other psychiatric conditions (Hedman-Lagerlöf et al., 2023). The treatment content is typically manualised and accessible online via a computer or mobile phone, and therapist guidance is provided remotely. When patients are encouraged to take on a more active role in their treatment, patient engagement could be enhanced and foster a sense of self-efficacy, which is particularly beneficial for individuals with PTSD facing negative self-cognitions.

The evidence base for the effectiveness of therapist-guided internet-delivered treatments for PTSD is accumulating. Simon et al. (2021) conducted a Cochrane review that revealed that internet-based cognitive behavioural therapy outperformed a waiting list in reducing PTSD symptoms, with a standardised mean difference of 0.61. However, considerable variations in effect sizes were observed among different programmes, with certain therapist-assisted programmes demonstrating large to very large effects (Knaevelsrud et al., 2015; Lewis et al., 2017). Internet delivered prolonged exposure (Web-PE) has been found to effectively reduce PTSD symptoms in active-duty military personnel and veterans, although recruitment issues led to an RCT continuing as an uncontrolled trial. Web-PE and the control condition, in-person present-centred therapy, showed similar results in the RCT (McLean et al., 2021). In a recent large non-inferiority trial, no differences in treatment effects were found between a guided internet delivered CBT-T programme called Spring and face-to-face CBT-T in treating mild to moderate PTSD by the 16-week assessment point (Bisson et al., 2022). Another recent trial found that internet-based cognitive therapy for PTSD was superior to internet-based stress management therapy for the same target group (Ehlers et al., 2023). These combined findings have resulted in the NICE Early Value Assessment Guidance to recommend these digital treatment programmes for PTSD (Bisson et al., 2023).

The previous studies on internet-delivered CBT-T have reported significant decreases in symptoms of PTSD. However, these previous studies have mainly recruited participants with mild to moderate PTSD. More studies are therefore needed to investigate if this treatment format is effective and feasible also for individuals with more severe presentations of PTSD frequently found in regular care psychiatric settings. The primary objective of the study is to determine feasibility, acceptability, and safety for HOPE for that target group. HOPE could in the future help increase the availability of evidence-based psychological treatments for PTSD.

2. Material and method

2.1. Design

This was a single centre uncontrolled trial, that used independent assessors, performed at the publicly funded outpatient psychiatric setting in Stockholm, Sweden. Recruitment started on 18th October 2022 and ended on 3rd November 2022. Ethical approval was granted by The National Ethical Review Board in Sweden (registration ID: 2019-04413). The trial was registered on ClinicalTrials.gov on 23rd September 2022 before any participant was enrolled (registration ID: NCT05560854). All participants provided informed consent.

2.2. Participants

The eligibility criteria used were chosen to recruit a representative sample of patients with PTSD within outpatient psychiatric care in Sweden to ensure good external validity. Included participants were aged 18 years or older, diagnosed with PTSD as their primary condition, as per the criteria outlined in the Diagnostic and Statistical Manual of Mental Disorders, fifth edition (DSM-5) evaluated by the Clinician Administered PTSD Scale version 5 (CAPS-5; Weathers et al., 2018) had a stable dose of psychotropic medication for at least 4 weeks prior to study entry, were fluent in Swedish and signed informed consent. Exclusion criteria encompassed PTSD not being assessed as the primary diagnosis, the presence of severe psychiatric comorbidity like mania, psychosis, alcohol/substance use disorders or an immediate risk of suicide, requiring urgent clinical intervention, concurrent engagement in trauma-focused psychological treatment, and ongoing exposure to trauma-related threats (e.g. residing with a violent spouse).

2.3. Recruitment

Participants were recruited from a publicly funded outpatient psychiatric clinic in Stockholm and by self-referral in response to advertisements in social media. Interested applicants registered on a secure webpage and completed an online screening containing general demographic questions, questions about the index trauma, trauma history, a checklist of inclusion and exclusion criteria, and self-report questionnaires PTSD Checklist for DSM-5 (PCL-5: Weathers et al., 2013), Life Event Checklist (LEC-5: Gray et al., 2004), Alcohol Use Disorders Identification Test (Saunders et al., 1993) and Drug Use Disorders Identification Test (Berman et al., 2005) after signing informed consent. During the registration process, a user ID and password were created for each participant which was used to access the platform. For additional security, a two-factor authentication procedure was used. The webpage also contained information about the study including the principal investigator's contact details.

The applicants were then assessed based on the provided screening data by study personnel. If preliminary eligible, further assessment via a structured telephone-based clinical interview to determine if inclusion criteria were met, including the CAPS-5, was conducted. There were no physical study visits conducted on site. Applicants who did not meet the eligibility criteria were informed via phone and, if necessary, provided guidance on accessing regular care. Eligible participants completed the baseline assessment after which they were formally included in the study.

2.4. Therapists and assessors

The treatment was guided by three clinical psychologists and two resident psychologists at the recruitment site trained in prolonged exposure. The principal investigator MB had extensive previous experience in digital exposure-based treatment and is a certified trainer in prolonged exposure. The therapists received basic training in the use of digital treatment comprised a walk-through the digital platform used in the study. Therapists received weekly group clinical supervision specific to the trial by MB. MB also supervised directly in the platform and reviewed the feedback on homework assignments and communication with participants. No deviation from the treatment protocol was detected. The therapists treated at least three participants each. The follow-up assessments were carried out by assessors independent of the study with varying levels of clinical experience; clinical psychologists, psychologists fulfilling their practical obligations, and final-year students enrolled in a five-year clinical psychology programme. Supervision was provided by the first author. The all had received training in the CAPS-5 ranging from one day to a more comprehensive two-day period.

3. Treatment

HOPE comprises all core treatment elements in prolonged exposure which are considered a first line treatment for PTSD and is recommended in available treatment guidelines (e.g. Hamblen et al., 2019). HOPE is divided into six text-based modules that participants sequentially gain access to when the therapist deems that the participants have adhered to the previous module. To facilitate comprehension and ensure a shared understanding of the treatment components, each module concludes with a brief quiz assessing the content. Additionally, the treatment content is audio-recorded and available for streaming and downloading. The treatment is designed to be accessible through a variety of devices, including PC, laptop, tablet, and smartphones.

Each participant in this study had a designated therapist that guided them through treatment. The aim of the guidance was to offer support, monitor progress and provide individually tailored feedback on completed assignments, keep motivation up, and problem-solving. If a participant did not log in to the platform for three days or was late in submitting agreed upon exercises, the therapist either sent out reminders via the online platform in the form of short text messages or email or calls the participant by telephone. The participants were informed that they could expect to receive a response from their therapists through the email system within the digital platform within 48 h on weekdays.

The treatment programme includes five fictious case examples of individuals suffering from PTSD precipitated from exposure to different types of traumas (interpersonal/non-intentional/childhood/adulthood). These cases are used to illustrate common difficulties that may arise during exposure therapy, such as under-engagement and the use of safety behaviours. The participants can follow these cases throughout the treatment components to gain a better understanding of the treatment process.

The participants retain their recordings of imaginal exposure or written trauma narratives and do not submit them through the platform to the therapist. Digital worksheets are instead employed to not only assist participants in monitoring alterations in perceived emotional intensity and recognising shifts in negative beliefs related to themselves, others, or the world but also provide a tool for the therapist to track the participants’ progress. The duration for imaginal exposure adheres to research indicating no significant difference in treatment effectiveness among timeframes of 30, 20, or 10 min (Bryant et al., 2019; Nacasch et al., 2015; van Minnen & Foa, 2006), compared to the original 45-minute recommendation in the PE protocol (Foa et al., 2019) (Table 1).

Table 1. The treatment content in the six modules.

Module	Description
1: Introduction to the treatment and platform	Psychoeducation about trauma and PTSD. Overall rationale for treatment. Introducing breathing retraining to reduce general stress and arousal.
2: In vivo exposure	Rationale for in vivo exposure and instructions on how to gradually confront situations that are perceived as dangerous or triggering trauma-related distress but are objectively safe. Illustrations of common difficulties that may arise during in vivo exposure (e.g. the use of safety behaviours) and how to overcome them. Digital worksheets are used to help participants observe changes in perceived emotional intensity and notice changes in negative beliefs about themselves, others, or the world.
3: Imaginal exposure	Rationale for imaginal exposure and instructions on how to conduct imaginal exposure each day for 20-30 min and processing. Illustrations of common difficulties that may arise during imaginal exposure (e.g. over-engagement and under-engagement) and how to overcome them. Digital worksheets are used to help participants observe changes in perceived emotional intensity and notice changes in negative beliefs about themselves, others, or the world.
4: Common problems with exposure	Information about common problems that can occur while working with exposure and how to overcome them.
5: Hot spots	Rationale for the expansion of the imaginal exposure exercise to the most distressing sequences of the traumatic memory (i.e. hot spots) and how to conduct that. Digital worksheets are used to help participants observe changes in perceived emotional intensity and notice changes in negative beliefs about themselves, others or the world.
6: Relapse prevention	Summary of what the participant has learnt during treatment and make a relapse prevention plan. A digital worksheet is used to review progress, reflect upon how these changes were accomplished, and how to deal with any temporary increases in symptoms of post-traumatic stress in the future.

4. Outcomes

4.1. Primary outcome: feasibility and acceptability

The study procedures and provision of the intervention were assessed for feasibility by assessing level of treatment and assessment engagement, participants’ overall satisfaction with the intervention, and the frequency of reported adverse events related to treatment. Treatment satisfaction was measured using the Client Satisfaction Questionnaire (CSQ-8; Larsen et al., 1979) immediately after treatment completion. The CSQ-8 comprises eight items rated on a 4-point Likert-type scale with a total sum score ranging from 8 to 32. Higher scores reflect greater satisfaction. The instrument has been found to have sound psychometric properties (Nguyen et al., 1983). We considered level of intervention usage, adverse events related to treatment, and level of drop out indicative of intervention acceptability.

4.2. Secondary outcome measures

Trained assessors assessed the severity of PTSD symptoms over the past month using the CAPS-5 at two time points: one month and six months after the completion of the treatment. The CAPS-5 assesses the severity of the 20 DSM-5 PTSD symptoms on a scale from 0 to 4, yielding a total sum score of 80. Additionally, it provides a diagnosis of PTSD for the past month. The CAPS-5 total severity score has high internal consistency (Cronbach’s α = 0.88) and inter-rater reliability (intraclass correlation coefficient  = 0.91), and good test-retest reliability (intraclass correlation coefficient = 0.78) (Weathers et al., 2018).

All self-report secondary measures were administered via the digital platform. The PCL-5 and The International Trauma Questionnaire (ITQ) were used to evaluate self-rated symptoms of PTSD and complex PTSD symptoms as outlined in the DSM-5 and in the upcoming ICD-11. The PCL-5 assesses the 20 PTSD symptoms outlined in the DSM-5 over the past month, utilising a four-point scale. This results in a total symptom severity score ranging from 0 to 80, where higher scores indicate greater severity (Blevins et al., 2015). The PCL-5 has a high internal consistency (alpha = 0.95) and good test-retest reliability (Blevins et al., 2015; Bovin et al., 2016). In a Swedish sample, a cutoff of 29 has been identified as indicative of probable PTSD (Bondjers, 2020). The ITQ consists of 12 items grouped into three symptom clusters related to PTSD (re-experiencing, avoidance, and sense of threat) and three additional clusters related to DSO (Disturbances in Self-Organisation: affective dysregulation, disturbances in relationships, and negative self-concept). Responses are rated on a 5-point Likert scale (0-4), with a score of ≥ 2 indicating symptom presence. For a probable PTSD diagnosis, at least one symptom from each PTSD cluster is required, while a complex PTSD (C-PTSD) diagnosis additionally necessitates one symptom from each DSO cluster. The ITQ has been validated as a reliable measure for assessing C-PTSD based on the ICD-11 criteria (Cloitre et al., 2018).

The Patient Health Questionnaire (PHQ-9; Kroenke et al., 2001) was used to assess symptoms of depression aligned with DSM-IV criteria for major depressive disorder. Respondents rate the frequency of experiencing specific depression symptoms over the past two weeks on a four-point scale, ranging from ‘not at all’ to ‘most days.’ The PHQ-9 generates a severity score ranging from 0 to 27, as each of the nine items can be scored from 0 (not at all) to 3 (nearly every day) and has been found to have sound psychometric properties (Kroenke et al., 2001).

The EQ-5D, a generic measure gauging health status across five dimensions: mobility, self-care, usual activities, pain/discomfort, and anxiety/depression, was used to assess health-related quality of life. Each dimension comprises three response levels (no problems, some problems, and unable to/extreme problems). The EQ-5D accounts for a total of 243 unique health states, and findings can be presented either dimension-wise or as a unified index score (Rabin & de Charro, 2001). In this study, we calculated the single index score.

4.3. Safety procedures

Participants were assessed weekly during the treatment period using the PCL-5 and ITQ to evaluate treatment effects and enable therapists to adapt interventions based on changes in symptoms or initial symptom exacerbation. In addition, participants were asked to report any adverse event using a self-report questionnaire that was administered weekly through the treatment period, post-treatment and at the 1-month and 6-month follow-up.

5. Statistical analyses

The statistical analyses were calculated in STATA 17.0 per the intention-to-treat principle if not otherwise stated. Linear mixed effects models with time as an independent variable and secondary outcome measures as dependent variables were carried out to investigate if HOPE was associated with reductions in symptoms of PTSD, depression and an increase in quality of life. The models comprised fixed effects for time and a random intercept for individuals.

6. Results

Figure 1 shows the participant flow through the study. Out of the thirty-six applicants who completed the digital online screening, thirty participants were recruited and started HOPE. The most common reason for exclusion was that the applicant declined to participate in the study at the time of assessment.

Figure 1. Participants flow in the trial.

The characteristics of the recruited sample are presented in Table 2. The sample predominantly comprised women (80%), with a mean age of 36 years (SD = 12). The majority (80%) of participants had concurrent psychiatric diagnoses, including depression, ADHD, and autism spectrum disorder. Approximately 46% of participants were from the Stockholm region, while the rest represented various locations across Sweden. On average, participants reported exposure to 2.33 traumatic events, with a mean time from the index trauma to treatment of 16.8 years. Around half reported that they had been victims of childhood trauma.

Table 2. Clinical characteristics and sociodemographic of the sample (N = 30).

Gender, n (%)	Women	24 (80)
	Men	3 (10)
	Non-binary	3 (10)
Age	Mean (SD)	36 (12)
	Range	18–65
Highest education, n (%)	College/university	10 (33)
	High school	15 (53)
Occupational status, n (%)	Working full time	11 (37)
	On sick leave	7 (23)
Current psychiatric comorbidity n (%)	Any	24 (80)
	Depression	12 (40)
	ADHD	5 (17)
	Autism spectrum disorder	3 (10)
	Personality disorder, any	2 (7)
Type of trauma, n (%)	Rape/sexual assault/abuse	16 (53)
	Threat of death	6 (20)
	Physical assault	3 (10)
	Witnessed sudden death	3 (10)
	Witnessed sexual or physical assault	2 (7)
Time from index trauma, mean year (SD)	Mean (SD)	16.8 (15.40)
	Range	0.60–59
Number of reported traumatic events, mean (SD)	Mean (SD)	2.33 (1.73)
	Range	1–8
Current stabilized medication, n (%)	SSRI	24 (80)

The participants’ symptom severity was characterised by moderate to severe posttraumatic stress disorder. Ninety-three percent of the sample met self-reported criteria for ICD-11 complex PTSD (Cloitre et al., 2013). The average baseline total sum score on the CAPS-5 was 40.40 (SD = 9.04) and 49.16 points (SD = 10.08) on the self-administered PCL-5.

6.1. Treatment and assessment engagement

Among the participants, sixty-four percent completed the exposure-based portion of the treatment, thus completed a minimum of three treatment modules, while thirty-two percent completed all six treatment modules. Participants logged into the platform approximately twice a week, with a mean of 19.6 logins during the 10-week intervention period (SD = 11.8). Additionally, they sent on average 13 messages to their therapists throughout the treatment period (SD = 11.47).

Five participants (17%) dropped out from the treatment, mainly citing that internet-delivered treatment was not suitable for them. The level of data attrition at our primary endpoint was high, reaching 17%.

The platform recorded the quantity of messages and the duration of therapist interactions with participants. On average, therapists sent 22 messages (SD = 11.71) during the ten-week treatment period. The average time spent by therapists per participant per week throughout the entire treatment period was 13 min (SD = 12).

6.2. Satisfaction with treatment

The participants’ mean score on the CSQ-8 was 22 (SD = 5.87), indicating overall satisfaction with HOPE. Only five participants reported that they would not recommend HOPE to a friend facing similar difficulties.

6.3. Adverse events

Twenty three percent of participants reported a total of 62 minor adverse events attributed to the treatment during the treatment period that could be conceptualised as initial symptoms exacerbation (e.g. increase in anxiety, intrusive memories, nightmares, and overall stress).

6.4. Secondary outcomes

More detailed information can be found in Table 3. The analysis using mixed effects models revealed significant effects from baseline to the 1-month follow-up on the CAPS-5 (mean points reduction = −13.58, SE = 2.41, [95% CI −18.30 to −8.85], p < .001). The within-group effect size was large, Cohen's d = 1.30 [95% CI −1.79 to −0.82]. Ten participants who completed the 1-month follow-up still met diagnostic criteria for PTSD.

Table 3. Secondary outcome measures at baseline, post-treatment and 1-month and 6-month follow up.

Within-group effect sizes
	BASELINE	POST	1-MONTH FU	6-MONTH FU	BASELINE to POST	BASELINE to 1-month FU	BASELINE to 6-month FU
Clinical administered measure	M (SD)	M (SD)	M (SD)	M (SD)	Cohen's d (CI-CI+)	Cohen's d (CI- CI+)	Cohen's d (CI- CI+)
CAPS-5	41.73 (8.84)	-	28.66 (12.17)	24.66 (12.70)	-	1.35 (0.90-1.80)	1.44 (0.96-1.94)
Self-administered measures
PCL-5	49.16 (10.08)	32.8 (17.1)	30.10 (14.5)	28.27 (17.12)	1.22 (0.60- 1.83)	1.43 (0.80-2.04)	1.70 (0.90-2.47)
ITQ	31.90 (8.15)	20.61 (9.96)	21.15 (11.76)	18.90 (11.17)	1.34 (0.60- 1.83)	1.15 (0.44-1.83)	1.42 (0.63-2.20)
PHQ-9	15.73 (6.04)	11.44 (6.67)	11.23 (8.09)	10 (7.80)	0.68 (0.07- 1.27)	0.67 (0.01-1.33)	0.88 (0.10-1.65)
EQ-5D	0.44 (0.35)	0.52 (0.32)	0.50 (0.37)	0.64 (0.2)	0.22 (−0.82–0.35)	0.14 (−0.78–0.51)	0.26 (0.06-0.32)

Abbreviations: CAPS-5, Clinician-Administered PTSD Scale for DSM-5; FU, follow-up; ITQ, The International Trauma Questionnaire; M, means; PCL-5, PTSD Checklist for DSM-5; PHQ-9, Patient Health Questionnaire; POST, post-treatment; SD, standard deviation.

Significant improvements were observed both in symptoms of PTSD and complex PTSD from baseline to post-treatment (PCL-5: mean points reduction per treatment week = −1.38, SE = 0.21, [95% CI −1.79 to −0.99], p < .001, ITQ: mean points reduction per treatment week = − 0.90, SE = 0.11, [95% CI −1.13 to −0.67], p < .001) corresponding to large within-group effect sizes. Responders were classified as those who achieved a reduction of ≥10 points on the PCL-5, accounting for 50% of the study participants.

In relation to non-disorder-specific outcome measures, the mean point reduction from baseline to immediately after treatment of 4.28 points on PHQ-9, used to measure level of depressive symptoms, was statistically significant (p < .05 [95% CI −0.96 to −0.62]). The increase in quality of life was not statistically significant immediately after treatment as indicated by EQ-5D (p = .60). These results were sustained at the 1-month follow up. The rate of responders, as measured by the PCL-5, was 67% at the 1-month follow-up point. Seven participants, however, still met self-rated criteria for complex PTSD.

6.5. follow-up

The 6-month follow-up was completed by 21 participants (70%), demonstrating the sustained effects of the treatment.

7. Discussion

This is the first study to investigate the feasibility of a therapist-guided digital treatment for PTSD in regular psychiatric care in a sample characterised by severe and complex PTSD. The findings suggest that HOPE was feasible, acceptable, and preliminary effective when using therapists with no previous background in digital treatments. Treatment engagement and adherence to treatment was high and the need for clinical resources was modest. The dropout rates for HOPE were similar to face-to-face treatment (Imel et al., 2013). All dropouts occurred before or just after logging into the treatment platform without completing any modules. This suggests that reluctance to engage in digital treatment might be a factor, rather than issues related to the tolerability of the treatment content itself. The absence of any reported serious adverse effects supports the acceptability of HOPE, although some participants experienced initial symptom exacerbation.

The results indicated clinically meaningful improvements on symptoms of both PTSD and complex PTSD. The large within-group effect sizes found are comparable to those observed in a prior internet-based CBT study for PTSD conducted within a clinical context (Spence et al., 2011). Similar patterns emerged for symptoms of depression and quality of life, albeit with smaller effect sizes. The proportion of participants who no longer met criteria for a DSM-5 PTSD diagnosis at the 1-month follow up (50% of the whole sample, 66% of those who completed the 1-month follow up) or were classified as responders, as measured by the PCL-5 (67%) aligns with those observed in RCT:s for face-to-face treatment. The typical response rates reported typically fall within the range of 40-60% (Loerinc et al., 2015). These positive outcomes were obtained with as little as a mean of two hours and ten minutes of therapist time per participant. This can be contrasted with the standard 8–15 week treatment format of 90-minute face-to-face sessions that is typically used for administering prolonged exposure therapy (Foa et al., 2019). Notably, the level of therapist involvement in guiding HOPE was considerably lower compared to two recently published randomised controlled trials on I-CBT for PTSD (Bisson et al., 2022; Ehlers et al., 2023). In those studies, the mean therapist time spent per participant was 3.5 and 6.7 h respectively. The preliminary treatment effects in this study also differed from those studies and were found to be significantly lower. It is possible that some participants might have benefited from more therapist support and/or a longer treatment period. The optimal amount of guidance required for effective outcomes remains unclear. Further research is needed to better understand the role of therapist involvement and treatment duration in internet-based treatment for PTSD. However, it is important to note that the abovementioned trials specifically aimed to recruit individuals with mild to moderate PTSD in primary care settings and thus, the target groups differed. The differences in outcomes could also be interpreted that internet-based treatments for PTSD are less effective for patients with a more severe presentation of PTSD.

Given the prevalence of PTSD, therapist availability, and the pressures on health services, a crucial future research objective should focus on innovative ways to reduce therapist guidance time while maintaining treatment effectiveness. Treatment programmes like HOPE might be easier to implement in a regular care setting considering that therapist availability and too high case-load in therapists that prevents them from scheduling patients for weekly 90-minute appointments are common barriers to implementing evidence based treatment for PTSD (Finch et al., 2020). (Bisson et al., 2023) suggests that the development of accurate algorithms for effective artificial intelligence support within digital programmes could be a way forward, keeping ethical and acceptability considerations in mind.

8. Limitations

The study comes with some important limitations to consider. The study had a small sample size, and the absence of a control group limits the ability to draw definitive conclusions about treatment efficacy. The follow-up period after treatment was 6 months, which might not provide sufficient time to capture the long-term effects of treatment. The high proportion of missing data makes the 6-month results more uncertain, thereby complicating the process of comparing our findings to those of previous studies. Furthermore, no interrater reliability data between assessors were collected on the CAPS-5.

The strengths of the current study were that it was carried out in a routine psychiatric setting with a sample mainly consisting of patients who had experienced multiple childhood trauma and met criteria for self-reported ICD-11 Complex PTSD already in contact with psychiatry which makes the results likely to be generalisable of this population. The reach of treatment was high with few excluded applicants. The gold standard clinical interview CAPS-5 that assesses PTSD symptom severity and past month diagnosis of PTSD were used as primary clinical outcome measure.

8. Conclusions

Addressing conventional barriers to PTSD treatment is crucial due to the substantial treatment gap. The findings of this study suggest that HOPE is a feasible, acceptable, and confers clinically meaningful treatment effects for individuals affected by moderate to severe PTSD and self-rated complex PTSD. Future research should include larger randomised trials with an active control group to further evaluate its effectiveness. More research is also needed on characteristics of who benefits from treatment and how much therapist support is needed for optimal results.

Ethical standards

The authors assert that all procedures contributing to this work comply with the ethical standards of the relevant national and institutional committees on human experimentation and with the Helsinki Declaration of 1975, as revised in 2008.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Data availability statement

The raw data supporting the conclusions of this article will be made available by the authors upon request given that the request comply with Swedish and EU laws regulating protection of identifiable data.

Additional information

Funding

This work was supported by Innovationsfonden [FoUI 982623]. The funding organization did not have any role in the conception of the study design or in the collection, analysis, or interpretation of the data, in the writing of the report, or in the decision to submit the paper.