Does treatment specific-, disorder specific- or general therapeutic competence predict symptom reduction in posttraumatic stress disorder?

ABSTRACT

Background: Literature on the association between therapist competence and treatment success in posttraumatic stress disorder (PTSD) treatments is scarce and results are mixed.

Aims/Objective: The relationship between different types of therapeutic competence, therapeutic alliance, and PTSD symptom reduction in patients treated with Dialectical Behaviour Therapy for PTSD (DBT-PTSD) or Cognitive Processing Therapy (CPT) was assessed. Competence types were PTSD-specific competence, treatment specific competence, and general competence in cognitive behaviour therapy (CBT).

Method: Videotaped therapy sessions from N = 160 women with PTSD and emotion regulation difficulties after child abuse participating in a large randomised controlled trial (Bohus et al., 2020) were rated. Three therapeutic competence-types were assessed using specifically developed rating scales. Alliance was assessed via patient ratings with the Helping Alliance Questionnaire (HAQ). PTSD symptoms were assessed at pre- and post-treatment via clinician rating with the Clinician-Administered PTSD Scale for DSM-5 (CAPS-5) and via self-rating with the PTSD-Checklist for DSM-5 (PCL-5).

Results: No significant association between competence and clinician or self-rated PTSD symptoms was found. PTSD specific competence predicted clinician rated PTSD symptom severity on a trend level. Alliance predicted both clinician and self-rated PTSD symptom reduction.

Conclusion: Our results provide a starting point for future research on different competence types and their association with PTSD treatment gains. Therapists were highly trained and received weekly supervision, hence a restricted competence range is a possible explanation for non-existing associations between competence and PTSD symptom reduction in our sample. More research in naturalistic settings, such as dissemination studies, is needed.

HIGHLIGHTS

• Three different types of therapeutic competence and their association to treatment gains in women with posttraumatic stress disorder after child abuse were assessed.

• Therapist competence was high in all three domains of competence.

• No association was found between any of the competence types and reduction in posttraumatic stress disorder symptoms.

Antecedentes: La literatura sobre la asociación entre la competencia del terapeuta y el éxito del tratamiento en el trastorno de estrés postraumático (TEPT) es escasa y los resultados son contradictorios.

Objetivos: Se evaluó la relación entre los diferentes tipos de competencia terapéutica, la alianza terapéutica y la reducción de los síntomas del TEPT en pacientes tratados con Terapia Dialéctica Conductual para el TEPT (DBT-TEPT por sus siglas en inglés) o Terapia de Procesamiento Cognitivo (TPC). Los tipos de competencia fueron competencia específica para el TEPT, competencia específica para el tratamiento y competencia general en terapia cognitivo-conductual (TCC).

Método: Se evaluaron las sesiones de terapia grabadas en vídeo de N = 160 mujeres con TEPT y dificultades en la regulación de las emociones tras maltrato infantil que participaban en un gran ensayo controlado aleatorizado (Bohus et al., 2020). Se evaluaron tres tipos de competencia terapéutica utilizando escalas de valoración específicamente desarrolladas. La alianza se evaluó a través de las valoraciones de los pacientes con el Cuestionario de Alianza de Ayuda (HAQ por sus siglas en ingles). Los síntomas de TEPT se evaluaron antes y después del tratamiento mediante la valoración del clínico con la Escala de TEPT administrada por el clínico según el DSM-5 (CAPS-5) y mediante la autovaloración con la lista de chequeo de TEPT según el DSM-5 (PCL-5).

Resultados: No se encontró ninguna asociación significativa entre la competencia y los síntomas de TEPT autoevaluados o evaluados por el clínico. La competencia específica para el TEPT predijo la gravedad de los síntomas de TEPT calificados por el clínico en un nivel de tendencia. La alianza predijo tanto la reducción de los síntomas de TEPT evaluados por el clínico como los autoevaluados.

Conclusiones: Nuestros resultados proporcionan un punto de partida para futuras investigaciones sobre los diferentes tipos de competencia y su asociación con los beneficios del tratamiento del TEPT. Los terapeutas estaban altamente capacitados y recibían supervisión semanal, por lo tanto, un rango de competencia restringido es una posible explicación para la inexistencia de asociaciones entre la competencia y la reducción de los síntomas de TEPT en nuestra muestra. Se necesitan más investigaciones en entornos naturalistas, como estudios de difusión.

背景：关于创伤后应激障碍（PTSD）治疗中治疗师胜任力与治疗成功之间关联的文献很少，结果混杂。

目的/目标：评估接受PTSD辩证行为疗法（DBT-PTSD）或认知加工疗法（CPT）治疗的患者不同类型治疗胜任力，治疗联盟和PTSD症状减轻之间的关系。胜任力类型是PTSD特定胜任力、治疗特定胜任力和认知行为治疗（CBT）的一般胜任力。

方法：对参加一项大型随机对照试验（Bohus 等人，2020 年）的 N = 160 名儿童虐待后患有PTSD和情绪调节困难的女性的录像治疗课程进行了评分。使用专门开发的评分量表评估了三种治疗胜任力类型。联盟通过患者评分与帮助联盟问卷（HAQ）进行评估。在治疗前后通过临床医生管理DSM-5 PTSD量表（CAPS-5）进行评分，并通过DSM-5 PTSD检查表（PCL-5）进行自我评估，从而评估PTSD症状。

结果：胜任力与临床医生或自我评估的PTSD症状之间没有发现显著关联。PTSD特定胜任力在趋势水平上预测临床医生评估PTSD症状严重程度。联盟预测临床医生和自评PTSD症状减轻。

结论：本研究结果为未来研究不同胜任力类型及其与PTSD治疗获益的关系提供了起点。治疗师训练有素，每周接受督导，因此胜任力范围有限是胜任力与PTSD症状减轻之间不存在关联的可能解释。需要在自然环境中进行更多的研究，例如传播研究。

KEYWORDS:

• Posttraumatic stress disorder
• treatment integrity
• therapeutic competence
• PTSD-specific competence
• treatment specific competence
• dialectical behaviour therapy for PTSD
• COGNITIVE processing therapy

PALABRAS CLAVE:

• Trastorno de estrés postraumático
• integridad del tratamiento
• competencia terapéutica
• competencia específica para el TEPT
• competencia específica para el tratamiento
• terapia dialéctico-conductual para el TEPT
• Terapia de Procesamiento Cognitivo

关键词:

• ：创伤后应激障碍；治疗完整性；治疗胜任力；PTSD特定胜任力；治疗特定胜任力；PTSD辩证行为疗法；认知加工疗法

1. Introduction

Trauma-focused psychological treatments have been shown to be effective treatments for posttraumatic stress disorder (PTSD; Lewis et al., 2020). Treatment guidelines recommend numerous cognitive behavioural therapies as first line treatments for PTSD, including cognitive therapy, prolonged exposure, or cognitive processing therapy (CPT; Resick et al., 2016). In a recent randomised controlled trial (Bohus et al., 2019; Bohus et al., 2020), CPT was compared to dialectical behaviour therapy for PTSD (DBT-PTSD, Bohus et al., 2013; Steil et al., 2011), a treatment specifically developed for patients with PTSD and emotion regulation difficulties. In both treatments statistically and clinically significant reductions in symptoms of PTSD were observed with DBT-PTSD being more effective than CPT (Bohus et al., 2020). This study aligns with previous findings supporting general efficacy of trauma-focused treatments. Yet not all patients benefit in the same way from treatments like CPT and DBT-PTSD. For trauma-focused therapies, as well as for psychotherapy in general, there is a gap in the precise understanding of how psychotherapies impede or facilitate therapeutic change (Kazdin, 2007). In the context of psychotherapy research, processes that occur between patient and therapist are hypothesised and studied as predictors of changed (de Orlinsky & Howard, 1986).

One therapist specific factor that has been studied as a mechanism of change is therapeutic competence. Therapeutic competence refers to the knowledge and skilfulness with which a treatment is applied (Waltz et al., 1993). Together with the domains of adherence (the level to which specific elements and procedures described in the treatment manual were used) and treatment differentiation (the degree to which strategies from other therapy forms were used), therapeutic competence is part of the concept of treatment integrity (Perepletchikova et al., 2007; Waltz et al., 1993). In the pursuit of finding possible predictors of symptom change, the assessment of treatment integrity has been pointed out as being a process that can help to gain insights on change mechanisms in clinical trials in general (Perepletchikova & Kazdin, 2005) and in PTSD treatments specifically (Barber, Triffleman, et al., 2007).

Findings on the association between competence and treatment outcome are mixed. In one meta-analysis, including 36 psychotherapy studies, weak to no associations between competence and clinical outcome were found (Webb et al., 2010). In a more recent meta-analysis, authors performed separate analyses for studies with hierarchical and non-hierarchical analyses and found small-to moderate positive associations between competence and treatment outcome, but only for non-hierarchical studies (Power et al., 2022). In both meta-analyses the type of disorder targeted in the studies emerged as a moderator between outcome and competence: Webb et al. (2010) found that studies targeting depression showed greater associations between competence and outcome, Power et al. (2022) found this moderating effect in studies targeting depression and anxiety.

Only very few studies have studied the role of therapeutic competence in the context of trauma-focused treatments of PTSD. A relationship between competence in a trauma specific treatment and the reduction of PTSD symptoms has been shown in the context of CPT. Higher competence in CPT predicted lower self-reported PTSD symptoms in the subsequent session in a study by Keefe et al. (2021). Furthermore, competence interacted with therapeutic alliance. When both competence and alliance were high, the reduction of PTSD symptoms in the next session was especially high (Keefe et al., 2021). In an implementation-effectiveness study, in which CPT sessions where rated for treatment fidelity, higher competence ratings showed a positive association with posttraumatic stress symptom reduction (Marques et al., 2019). In another study on the effect of adherence to and competence in four central elements of CPT, authors found that higher therapist competence in socratic questioning and in the CPT element ‘prioritizing assimilation before overaccommodation’ were related to greater PTSD symptom improvement over the course of treatment. Therapeutic competence in the other two central CPT components (‘attention to practice assignments’ and ‘emphasis on expression of natural affect’) was not related to PTSD symptom improvement (Farmer et al., 2017).

To be able to draw conclusions about the relationship between therapist competence and treatment outcome, it is crucial that competence is measured in a methodologically sound way. Recommendations for a methodological sound assessment of therapeutic competence and treatment integrity in general include a systematic rating of videotaped therapy sessions, use of psychometrically validated rating scales, ratings by more than one rater, and random selection of therapy sessions to be rated, preferably from different phases of therapy (Hogue et al., 1996; Weck et al., 2019).

Whereas the measurement of the treatment integrity element adherence relies on the treatment manual that is used, which means checking if interventions described in the manual are being used or not, the definition and hence the measurement of therapeutic competence is more challenging. It greatly depends on the context (e.g. patient behaviour, underlying theory of the treatment, setting of the therapy) in which the therapist behaviour can be seen as competent (Waltz et al., 1993). Therefore, therapeutic competence assessment requires both qualified raters and validated instruments. One widely used and psychometrically validated rating instrument for the assessment of therapeutic competence is the Cognitive Therapy Scale (CTS; Young & Beck, 1980). While the CTS assesses more global competencies in the field of cognitive therapy, different domains of therapeutic competence have been postulated to account for the complexity of the construct (e.g. Barber, Sharpless, et al., 2007; Kaslow, 2004). Barber, Sharpless, et al., (2007) differentiate between global competence and limited-domain competences. Global competence is defined as a broader concept of clinical skills and knowledge, limited-domain competences are ‘expressed within the context of a specific psychotherapy intervention or treatment modality’ (Barber, Sharpless, et al., 2007) and can therefore be treatment- or disorder specific. For the measurement of these specific competence domains, only few instruments exist, and consequently, the effects of those different competence domains on treatment outcome have rarely been studied. In one study by Ginzburg et al. (2012), authors reported that treatment-specific competence in cognitive therapy for social phobia predicted treatment outcome. To our knowledge no previous study examined whether treatment- or disorder specific competence predict the outcome of PTSD treatments.

To be able to measure different domains of competence, our workgroup developed rating scales to measure PTSD-specific competence, as well as treatment specific competence to CPT (Dittmann et al., 2017) and DBT-PTSD (Steil et al., 2022). With these rating scales, a very fine-grained and methodologically sound assessment of therapeutic competence was possible, allowing for identification of therapeutic competences that are related to symptom improvement in PTSD treatments.

Apart from the appropriate therapeutic competence assessment, it is important to consider potential influential factors when investigating the association between competence and PTSD treatment outcome (Barber, Triffleman, et al., 2007). Therapeutic alliance has been found to be both an important predictor of change in trauma-focused therapy (Cloitre et al., 2004; Ehlers et al., 2021) as well as a mediator between competence and treatment outcome (Weck et al., 2015). Therefore, we assessed and included therapeutic alliance in our examination of the role of therapeutic competence on PTSD treatment gains.

The aim of the present study was to assess if the therapeutic competence domains of PTSD-specific competence, treatment-specific competence, and/or general CBT competence are associated with PTSD symptom reduction in patients with PTSD treated with either CPT or DBT-PTSD while controlling for therapeutic alliance. We hypothesised that higher therapeutic competence in all three competence types would be related to greater PTSD symptom reduction from pre- to post-therapy.

Because patients in our study were treated with two different trauma-focused therapies, we also exploratorily assessed if the three competence types had a different effect in each treatment.

2. Method

2.1. Procedure

2.1.1. Clinical trial

The data for this study originate from the RELEASE study (RELEASE study, German Clinical Trials Registration ID: DRKS00006095). The RELEASE study was a large multicentre randomised controlled clinical trial that compared the efficacy of the newly developed therapy programme DBT-PTSD (Bohus et al., 2013; Steil et al., 2018) to the well-established trauma-focused treatment CPT (Müller-Engelmann et al., 2016; Resick et al., 2016) in women with PTSD and emotion regulation difficulties after childhood abuse. The study was conducted at three sites in Germany. Approval was obtained from the ethics committees of the three participating universities. Patients who met DSM-5 criteria of PTSD following sexual or physical abuse before the age of 18, who additionally reported three or more criteria of borderline personality disorder, including criterion six (affective instability), and who were available for 1 year of treatment were randomised in a 1:1 ratio to DBT-PTSD or CPT. Exclusion criteria were a lifetime diagnosis of schizophrenia, bipolar I disorder, intellectual disability, or severe psychopathology requiring immediate treatment in a different setting (e.g. a body mass index <.16.5); life-threatening suicide attempts within the last two months, current substance dependence, medical conditions contradicting exposure protocol (e.g. pregnancy), highly unstable life situation (e.g. homelessness), scheduled residential treatment and participation in either CPT or DBT-PTSD treatment during the last year. Both treatments consisted of up to 45 weekly sessions over the course of one year, and up to three monthly booster sessions in the following three months. Diagnostic assessments were administered at six assessment points: intake, three months, six months, nine months, 12 months and the end of treatment (after 15 months). Further details of the trial, such as the CONSORT flow diagram, can be found in the publication of the main results (Bohus et al., 2020), and the study protocol (Bohus et al., 2019).

2.1.2. Treatments

DBT-PTSD is a multiple-components phase based programme of up to 45 weekly sessions and was specifically developed to meet the needs of patients with Complex PTSD. It is based on the principles of standard DBT (Linehan, 2014) but also contains trauma-focused cognitive–behavioural interventions, such as exposure (Ehlers et al., 2005; Foa et al., 2007), and techniques from compassion-focused therapy (Gilbert, 2010) and acceptance and commitment therapy (Hayes et al., 2011). Detailed information on DBT-PTSD can be found in Bohus et al. (2013) and Steil et al. (2011).

CPT (Resick et al., 2016) was chosen as the active control condition for the RELEASE study. CPT is a trauma-focused cognitive therapy, and a well-established treatment for patients with PTSD. For the RELEASE study, the CPT manual was adapted in close cooperation with the treatment developer P. Resick (Duke University, Durham, USA). To be comparable to DBT-PTSD the CPT manual for the RELEASE study comprised up to 45 sessions. Four sessions were included in the beginning of the treatment to establish the therapeutic relationship and to develop emergency plans to cope with suicidality and severe self-harm. The 12 original CPT sessions were administered afterwards in these sessions, focussing on the index trauma of the patient. From session 17 onwards, the further treatment can be adapted to the needs of the patient. The topics are derived from the patient’s stuck point log. Either the index trauma can be further focussed or, as patients with complex PTSD often experienced more than one traumatic event, also other traumatic events can be focused using the cognitive methods typical for CPT. For the RELEASE study, the ‘cognitive only’ version of CPT without a written account of the traumatic event was used. For further information see Müller-Engelmann et al. (2016).

2.1.3. Participants

Altogether, 193 participants were included in the RELEASE study (Bohus et al., 2020), and video recorded therapy sessions from 160 participants were rated. Therapy sessions of 33 participants could not be rated due to one of the following reasons: early drop out with no video recorded sessions available (23), withdrawal of consent for video ratings (4), and missing video recordings (6). Early remission was achieved by 11 patients, which means the patient recovered and was able to end therapy early. Such cases were counted as treatment completion and not as treatment dropouts. To achieve early remission, all of the following predefined conditions had to be fulfilled: (1) patient claimed recovery prior to session 45, (2) therapist agreed, (3) therapist’s supervisor agreed, (4) blind rater assessed that the patient no longer met PTSD diagnostic criteria.

The 160 women from whom ratings were available had a mean age of 36.75 years (SD = 10.95 years; range = 18–62 years) and did not differ on any of the outcome variables at baseline from the originally included sample. Therapy was completed according to protocol by 129 of the participants, who received between 12 and 45 h of therapy (M = 39.6 h; SD = 6.7 h). In 31 cases, patients dropped out before therapy was completed. These patients received between 4 and 39 h of therapy (M = 17.3 h; SD = 8.7 h). Participants who had a psychiatric hospitalisation of two weeks or longer or who missed six consecutive sessions were considered dropouts.

2.1.4. Therapists

Therapy was delivered by 49 therapists (43 female, 6 male); 26 delivered DBT-PTSD and 23 delivered CPT treatment. Therapists’ mean age was 32.67 years (SD = 5.18), and they had an average of 1.21 years (SD = 1.90) of experience with the treatments delivered in the study. All therapists were trained in a 4-day workshop in either DBT-PTSD or CPT, and 60% completed a pilot case preceding the trial. Therapists in both conditions had 1.5 h of group supervision per week and monthly case-consultations with the treatment developers. Both therapy groups were balanced regarding therapists’ characteristics such as experience, age, or number of treated patients (for more information see Bohus et al., 2020).

2.2. Variables and instruments

2.2.1. Clinical outcome measures

PTSD symptom severity was assessed as the primary outcome using the Clinician-Administered PTSD Scale for DSM-5 (CAPS-5; Weathers et al., 2018) in its German version, which has been psychometrically validated (Cronbach's alpha = .93; intraclass correlation coefficient (ICC) = .81–.89; Müller-Engelmann et al., 2020). The total score of the CAPS can range from 0 to 80, with higher scores indicating greater symptom severity. Furthermore, self-rated PTSD symptom severity was measured by the PTSD Checklist for DSM-5 (PCL-5; Weathers et al., 2013) in its German version which has excellent psychometric properties (Cronbach's alpha = .95; test-retest reliability r = .91; Krüger-Gottschalk et al., 2017). The PCL-5 total score can also range from 0 to 80 with higher scores indicating greater symptom severity. Both outcome measures were administered at all six assessment points.

2.2.2. Assessment of therapeutic competence

Raters. Two independent raters watched video recordings of therapy sessions and assessed therapeutic competences. Both raters were licensed cognitive behavioural therapists with 3 and 8.5 years of clinical experience, respectively. They had participated in workshops on both treatments, and they had also treated patients with both CPT and DBT-PTSD under the supervision of the treatment developers. Furthermore, both raters were involved in the development of the competence rating scales. Three pilot cases for both treatments were assessed, and discrepancies were discussed to practice the administration of the scales before starting with assessments for this study. These pilot cases were not included in the present study. Both raters were blind to clinical outcome.

Rating Process. Two video recorded therapy sessions per patient, one from the first and one from the second half of the therapy, were randomly selected for the rating process. Video recordings from the first four sessions were not included. If a patient had dropped out before the second half of the treatment, only one video recording was randomly chosen and rated. From the CPT treatment, 136 video recordings were rated and from the DBT-PTSD treatment, 161 video recordings were rated. Hence, altogether 284 video recordings were rated and included in the analyses. From the CPT arm, 30 videos were doubly rated by both raters and 40 videos from the DBT-PTSD arm. Interrater-reliability for these doubly rated videos was calculated with the intraclass correlation coefficient (ICC) using Model 2 (ICC_(2,2); Shrout & Fleiss, 1979)

Competence Rating Scale. To assess therapeutic competence, we used a rating scale consisting of three parts: the first assessing global therapeutic competence in CBT, the second assessing PTSD-specific competence, and the third assessing treatment-specific DBT-PTSD and CPT competence respectively.

For measuring disorder-specific competence, we developed the Competence Rating Scale for PTSD (CRS-PTSD; Dittmann et al., 2017) which has shown good psychometric properties (Intraclass correlation coefficient (ICC) = .94 to .97; Dittmann et al., 2017). The scale was developed by surveying 22 internationally known experts in PTSD treatment, who identified the most important therapeutic competences in PTSD. From their answers, 7 items were developed to measure PTSD-specific competence on a 7-point Likert scale ranging from 0 = poor competence to 6 = excellent competence. Example items include ‘identification and modification of avoidance behavior’, ‘appropriate handling of the patient’s emotions’ or ‘managing PTSD-specific symptoms’. In our sample, interrater reliability of the CRS-PTSD was good with ICC = .95. For further information, see Dittmann et al. (2017).

To assess treatment-specific therapeutic competence, we developed one scale for each treatment (CPT and DBT-PTSD respectively). The Treatment Specific Competence Rating Scale for CPT (CRS-CPT) consists of four items that represent the most important skills in CPT that can be assessed in every CPT session. The same 7-point Likert scale ranging from 0 = poor competence to 6 = excellent competence was used. The CRS-CPT demonstrated good psychometric properties (ICC = .95 to .97; Dittmann et al., 2017). Example CRS-CPT items include ‘Identification and appropriate expression of stuck points’ or ‘use of socratic dialogue and other cognitive methods to modify stuck points/core beliefs’. The CRS-CPT showed good interrater reliability in our sample with ICC = .97 For further information, see Dittmann et al. (2017).

The Treatment Specific Competence Rating Scale for DBT-PTSD (Release Version; CRS-DBT-PTSD-R) consists of six items representing the therapeutic skills considered most important in DBT-PTSD. Example CRS-DBT-PTSD-R items include ‘Adequate skill development with respect to distress and emotion regulation’, ‘Focus on validation strategies’ or ‘promotion of a mindful and benevolent supportive attitude of the patient towards him-/herself’. Items are again rated on the same 7-point Likert scale. The CRS-DBT-PTSD-R provided good psychometric properties (Patient-level ICC = .98, Reliability α_p = .82; Steil et al., 2022). An English translation of the CRS-PTSD, the CRS-CPT, and the CRS-DBT-PTSD-R are provided in the supplement. The English translation of the scales has not yet been psychometrically validated.

For measuring global CBT competence, we used the already existing German adaptation of the CTS (Young & Beck, 1980). The German version (Weck et al., 2010) contains 14 items rated on a 7-point Likert scale ranging from 0 = poor competence to 6 = excellent competence and has shown good psychometric properties (ICC = .85 to 93; Weck et al., 2010). Additionally, we included one more item (Item 11: ‘Focus on the behavioral model’) to account for the use of this scale in more behaviourally oriented treatments. For the CTS, the overall interrater reliability in our sample was again high with ICC = .94.

For each of the three specific competence scales, the mean score can be calculated (range from 0 = poor competence to 6 = excellent competence), representing a therapist’s global CBT -, PTSD-specific- and treatment specific competence in CPT or DBT-PTSD.

2.2.3. Therapeutic alliance

Therapeutic alliance was measured using the Helping Alliance Questionnaire (HAQ; Bassler et al., 1995). With this 11-item questionnaire both the patient (HAQ-P) and the therapist (HAQ-T) are asked to rate statements related to therapeutic alliance (e.g. ‘I believe that my therapist is helping me. / I believe that I can help my patient.’) on a 6-point Likert scale ranging from 1 (No, I strongly feel the statement is not true) to 6 (Yes, I strongly feel the statement is true). Then a sum score is built that can range from 11 to 66, with higher scores indicating stronger therapeutic alliance. The HAQ was completed after every session by both therapist and patient. The reliability and validity of the German version of the HAQ has been demonstrated (Bassler et al., 1995). In the present study, we used the patients’ rating of alliance as patient rated alliance seems to be more strongly related to treatment outcome than alliance rated by the therapist (Barber et al., 1999).

2.3. Statistical analyses

To assess the relationship between the three therapeutic competences and clinician rated PTSD symptom reduction from pre- to post-treatment, we performed linear regression models with pre- to post difference of CAPS-5 and PCL-5 as the respective dependent variables. Independent variables were the three competence types and alliance. To obtain scores for the three competence types, we used the ratings of the videotaped therapy sessions. From each therapy, two sessions were rated, one from the first and one from the second halve of the treatment. In a first step, the means of the three competence scales (general competence, PTSD-specific competence, and treatment specific-competence in the CPT and DBT-PTSD group) were calculated. Then, these mean ratings from the first and second treatment halves were again averaged. This way, we received three competence scores for each therapist treating one particular patient (patient-therapist dyad).

The patients’ HAQ ratings were used as an alliance measure. We used the sum scores mean from the weekly ratings in the analyses. Missing HAQ data from 2 patients were imputed with the missForest package in R, which develops random forest models in an iterative process and can thereby impute continuous and categorical data in a non-parametric way (Stekhoven & Bühlmann, 2012). Welch’s t-tests were used to assess if there was a difference in the three competence types or therapeutic alliance between the DBT-PTSD and the CPT group. To assess the correlation between the three competence types and alliance, Spearman correlations were calculated.

In line with Bohus et al. (2020), missing data in the CAPS-5 and PCL-5 at post-treatment were imputed via multiple imputation on the scale level.

Hence, dependent variables could take on values both below and above zero. Higher positive values of the CAPS-5 or PCL-5 reduction depict a better symptom improvement whereas values close to zero represent no change in PTSD symptoms, values below zero indicate a worsening of the PTSD symptoms. Again, Welch’s t-tests were used to evaluate differences in PTSD symptom reduction between the two therapy groups.

Because of high correlations between the three competence types, separate linear regression models for each of the three competence types were investigated. PTSD-specific competence, treatment-specific competence, or general competence were entered into these models as the respective predictor variables. Furthermore, therapeutic alliance was entered as a control variable in the models.

In a second step, to assess if the three competence types had different effects in the two therapy groups, the interaction term competence type x group was added to the models. A two-tailed alpha-level of 0.05 was used when testing for statistical significance.

Cohen’s f² was calculated as a measure of effect size with levels of ≥.02, indicating small effects, ≥.15 medium effects, and ≥.35 large effects (Cohen, 2013).

3. Results

At baseline, participants had a mean CAPS-5 score of 40.12 (SD = 9.87). The mean reduction of the CAPS-5 from pre- to post was 19.75 points (SD = 14.67 points). There was no significant difference in CAPS-5 reduction between the DBT-PTSD group (mean CAPS-5 reduction = 21.22; SD = 14.35) and the CPT group (mean CAPS-5 reduction = 18.03; SD = 14.96, p = .17). Participants’ mean PCL-5 score at baseline was 49.21 (SD = 10.80). The mean pre- post reduction of the PCL-5 was 24.12 points (SD = 17.38), with a higher reduction in the DBT-PTSD group (mean PCL-5 reduction = 28.21, SD = 14.35) than in the CPT group (mean PCL-5 reduction = 19.37, SD = 18.22, p = < .01).

The mean scores for alliance, and the three different competence types in the entire sample as well as in the DBT-PTSD and the CPT group can be found in Table 1. Independent two-sided unpaired t-tests showed that PTSD-specific competence was higher in the DBT-PTSD group than in the CPT group. There were no differences between groups in the other competence types or the alliance. The frequency of the averaged competence ratings is displayed in Table 2.

Table 1. Means (M) and Standard deviations (SD) for the three competence types and alliance in the entire sample and in both therapy groups.

	Entire sample	DBT-PTSD	CPT
	M (SD)	M (SD)	M (SD)	p-value^a
PTSD-specific Competence^b	3.89 (.62)	4.00 (.64)	3.76 (.58)	.013
Treatment-specific Competence^b	3.86 (.77)	3.92 (.64)	3.80 (.90)	.30
General Competence^b	3.70 (.64)	3.68 (.65)	3.72 (.62)	.71
Alliance (rated by patient)^c	52.74 (6.51)	52.44 (5.81)	53.10 (7.23)	.52

^a Calculated from independent two-sided unpaired t-test.

^b The competence scores can range from 0 (not competent) to 6 (very high competence).

^c Alliance scores can range from 11 to 66.

Table 2. Frequency of competence ratings, averaged between first and second treatment half.

Rating	PTSD specific Competence	Treatment specific Competence	General Competence
0–.9	0	2	0
1–1.9	1	2	1
2–2.9	14	19	30
3–3.9	75	66	77
4–4.9	69	67	51
5–6	1	4	1

Note: 0 = poor competence; 1 = between poor and mediocre; 2 = mediocre competence; 3 = between mediocre and good; 4 = good competence; 5 = between good and excellent; 6 = excellent competence.

In Table 3 we present the correlations between the three different competence types and alliance. The three competence types were highly correlated with each other. Correlation between the competence types and therapeutic alliance was in a small to medium range, with treatment specific competence showing the highest correlation to alliance.

Table 3. Correlations between predictor variables.

	PTSD-specific competence	Treatment-specific competence	General competence	Alliance
PTSD-specific competence	–	.75***	.82***	.16*
Treatment-specific competence	–	–	.83***	.25**
General competence	–	–	–	.17*
Alliance	–	–	–	–

Note: ***p < .001; **p < .01; *p < .05.

3.1. Association between PTSD-specific competence and PTSD symptom severity reduction

Results of the models with PTSD-specific competence can be found in Table 4. There was a positive relation between PTSD-specific competence and CAPS-5 reduction from pre- to post-treatment, which was not significant (p = .054). Cohen’s f² was .02 indicating a small effect size. Hence, on a trend level, higher PTSD-specific competence was associated with greater pre- to post-reductions in clinician rated PTSD symptoms. Also, higher alliance was significantly related to higher pre- to post differences in the CAPS-5, Cohen’s f² was .16 which indicates a medium effect size.

Table 4. Linear regression models with PTSD-specific competence as predictor variable.

	CAPS-5 reduction					PCL-5 reduction
Fixed Effects	Est.	SE	t	p	Effect size, f^2	Est.	SE	t	p	Effect size, f^2
Intercept	19.75	1.06	18.56	<.001		24.12	1.26	19.16	<.001
PTSD-specific competence	2.1	1.08	1.95	.05	.02	1.35	1.28	1.06	.29	.01
Alliance	5.33	1.08	4.93	<.001	.16	6.84	1.28	5.35	<.001	.18

Note: Est.: Estimate; SE: Standard Error; CAPS-5: Clinician-Administered PTSD Scale for DSM-5; PCL-5: PTSD Checklist for DSM-5.

In the model for the PCL-5, PTSD-specific competence did not predict PCL-5 symptom reduction. Alliance predicted PCL-5 reduction from pre- to post-treatment. Hence, higher therapeutic alliance as rated by the patient was associated with higher reductions in both self-rated as well as clinician rated PTSD symptoms.

3.2. Association between treatment-specific competence and PTSD symptom severity reduction

No association between treatment specific competence and reduction in clinician rated PTSD symptom severity, measured by the CAPS-5 was found (see Table 5). Again, higher alliance was related to higher CAPS-5 reduction from pre-to post-treatment.

Table 5. Linear regression models with treatment specific competence as predictor variable.

	CAPS-5 reduction					PCL-5 reduction
Fixed Effects	Est.	SE	t	p	Effect size, f^2	Est.	SE	t	p	Effect size, f^2
Intercept	19.74	1.07	18.38	<.001		24.12	1.26	19.12	<.001
Treatment-specific competence	.96	1.11	.86	= .39	.01	.89	1.31	.68	=.50	.00
Alliance	5.42	1.11	4.86	<.001	.15	6.83	1.31	5.22	<.001	.17

Note: Est.: Estimate; SE: Standard Error; CAPS-5: Clinician-Administered PTSD Scale for DSM-5; PCL-5: PTSD Checklist for DSM-5.

The same pattern of results was found in the model for PCL-5 reduction. Treatment specific competence did not predict self-rated PTSD symptom severity, and higher alliance was a significant predictor of PCL-5 reduction from pre- to post.

3.3. Association between general CBT competence and PTSD symptom severity reduction

When general CBT competence was entered as a predictor into the model for CAPS-5 reduction, no significant effect of general CBT competence on CAPS-5 reduction from pre- to post-treatment became evident. Again, alliance predicted CAPS-5 reduction.

No association between PCL-5 reduction and general CBT competence was found, while alliance predicted PCL-5 reduction. Results of both models can be found in Table 6.

Table 6. Linear regression models with general CBT competence as predictor variable.

	CAPS-5 reduction					PCL-5 reduction
Fixed Effects	Est.	SE	t	p	Effect size, f^2	Est.	SE	t	p	Effect size, f^2
Intercept	19.75	1.08	18.37	<.001		24.12	1.26	19.09	<.001
General CBT competence	.87	1.09	.79	=.43	.00	.22	1.29.	.17	=.87	.00
Alliance	5.52	1.09	5.04	<.001	.16	7.02	1.29	5.46	<.001	.19

Note: Est.: Estimate; SE: Standard Error; CAPS-5: Clinician-Administered PTSD Scale for DSM-5; PCL-5: PTSD Checklist for DSM-5.

3.4. Effect of competence types on PTSD symptom reduction in two therapy groups

In a second step, an interaction term group x competence type was added to all models. This interaction term did not emerge as a significant predictor in any of the models.

4. Discussion

In the present paper, we assessed the relationship between PTSD treatment gains and three different types of therapeutic competence, namely PTSD-specific competence, general CBT competence and treatment specific competence to either DBT-PTSD or CPT while controlling for therapeutic alliance. Contrary to our initial hypothesis, reduction of clinician rated PTSD symptom severity from pre- to post- was not significantly related to one of the three competence types. However, there was a positive relationship between PTSD specific competence and the reduction of clinician rated PTSD symptom severity from pre- to post-treatment that did not reach statistical significance. No association was found between any kind of competence and reduction in patient self-rated PTSD symptom reduction.

Both clinician and patient-self rated PTSD symptom reduction were related to therapeutic alliance. A higher therapeutic alliance predicted higher PTSD symptom reduction from pre- to post-treatment. This finding goes in line with previous findings that underscore the importance of a good therapeutic alliance in the treatment of patients with PTSD (Beierl et al., 2021; Ehlers et al., 2021). Reasons for the importance of a strong working alliance in the treatment of patients with PTSD could for example be inherent to the nature of PTSD symptoms. Part of the PTSD symptomatology is avoidance, hence a particular good and trustful relationship to the therapist could be necessary to decrease this avoidance and to process traumatic incidents. Furthermore, we cannot rule out a reciprocal relationship between alliance and PTSD symptom reduction in our sample, in which symptom improvement predicts alliance ratings, like it has been demonstrated in other studies (Marker et al., 2013; Xu & Tracey, 2015).

Apart from the association between PTSD specific competence and clinician rated PTSD symptom reduction, none of the other competence types was associated with PTSD treatment outcome. Interpretation of our results indicates that therapeutic competence does not play a crucial role in the treatment of patients with PTSD. However, other studies have found effects of competence on PTSD treatment outcome (Farmer et al., 2017; Keefe et al., 2021; Marques et al., 2019). One reason why we did not find a relationship between competence and PTSD treatment gains in our study could be the restricted range of competence ratings in our sample. The majority of therapists in our study received ratings characterised as good therapeutic competence (between 3 and 5 on a scale ranging from 0 to 6; with means between 3.70 and 3.89 (SDs between .62 and .77)). Only very few therapists received ratings indicating either poor or excellent therapeutic competence.

As the data of this paper stem from a large multi-centre randomised controlled trial that assessed the efficacy of DBT-PTSD versus CPT, this restricted range and high level of therapeutic competence was desirable for this trial. It can be explained by thorough training and regular supervision of therapists in the RELEASE study, with all therapists being based at universities and having received significant training and supervision (Bohus et al., 2020). More data from trials with a larger competence range would be necessary to further assess the effect of competence on PTSD treatment success. Because a larger competence range contradicts internal validity and is not desirable in efficacy trials, larger dissemination studies are needed for the relationship between different forms of therapeutic competence in PTSD treatment outcome to be studied without restrictions in competence variance.

Furthermore, it is also possible that important aspects of therapeutic competence were not captured in our study. The PTSD-specific as well as both treatment specific competence scales were developed by our workgroup with the help of experts (Dittmann et al., 2017; Steil et al., 2022) and used for the first time in this study. Possibly, we missed aspects of PTSD-specific or treatment specific competences during our development process which are a crucial part of this construct. Also, it is conceivable that an entirely different domain of competence plays an important role in the treatment of patients with PTSD that was not included in our study.

However, on a trend level, an association between PTSD specific competence and clinician rated PTSD symptom reduction was found. This effect must be interpreted with caution, as it was only evident on a trend level. Yet this finding could point towards the importance of this special competence type in the treatment of patients with PTSD. As the scale was developed by our workgroup (Dittmann et al., 2017) and this paper is the first to use it to measure PTSD specific competence, there is no literature to compare our findings to. The scale was developed by using recommendations by PTSD treatment experts, who indicated which elements of therapeutic behaviour they see as specifically important in the treatment of PTSD patients. If these PTSD specific competence elements prove to have an effect on PTSD symptom reduction, there would be important implications for the training of trauma therapists independent of the particular manual which they are receiving training in. A training focus on the PTSD specific competences would be the logical implication. However, more research on PTSD specific competence is necessary before these implications are valid. Also, more research on the differentiation of the different competence types is necessary.

There are several limitations to our study. First, as priorly discussed, the restricted range of competence in our study is a limiting factor. As high levels of therapeutic competence were desirable for the original randomised controlled trial in terms of internal validity, for the purpose of finding an association between competence and treatment success, the data was not perfectly suitable. Future studies should include therapists with a broader competence range, from lower to excellent.

Second, we used competence rating scales that were specifically developed for this study. Even though this can also offer an advantage, especially as no other scales that measure specific competence to PTSD or DBT-PTSD exist, the use of these scales limits the comparability of our results to existing literature.

Third, our sample consisted of women with PTSD and symptoms of borderline personality disorder after child abuse. This highly selected sample limits comparability to the results of other studies that included different samples of PTSD patients with regards to traumatic incidents, patient gender, and patterns of comorbid symptoms.

Last, the associations between therapeutic competence and symptom reduction are characterised by complex interactions. Noticing that the patient reports or shows less or more symptomatology from session to session is likely to influence the therapists´ actions as much as vice versa. Also, therapeutic competence might be particularly important when using certain interventions, or at certain stages of the treatment. These complex interactions could best be studied using modern network analysis approaches. However, for such investigations, ratings of therapeutic competence as well as symptomatology would be needed for every single session. Assessing therapeutic competence using elaborate expert ratings after watching the whole session is time-consuming and expensive.

Despite these limitations, our study (1) highlights the importance of therapeutic alliance in predicting treatment outcome in PTSD und (2) provides an interesting starting point for future research on different competence types and their association to treatment gains in studies on PTSD treatment with a greater range of therapeutic competence.

Ethics declaration

This study approval was obtained from the independent Ethics Committee of the Medical Faculty Mannheim at Heidelberg University (Reference number: 2013–635N-MA). The study was also approved by the ethics committee of Goethe-University and Humboldt University. All subjects gave written informed consent in accordance with the Declaration of Helsinki.

Disclosure statement

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

Data availability statement

The data that support the findings of this study is available from the corresponding author, Regina Steil, upon reasonable request.