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. 2026 Mar 20;123(6):149–156. doi: 10.3238/arztebl.m2025.0239

Digital Acceptance and Commitment Therapy for the Treatment of Chronic Pain

Findings of a Randomized Controlled Efficacy Trial

Anne Etzelmüller 1,2,*,✉, Antonia Barke 3,*, Marie Feiler 2, Matthias Guth 4, Elena Heber 2, Harald Baumeister 5, David Daniel Ebert 1,2
PMCID: PMC13193243  PMID: 41607292

Summary

Background:

People with chronic pain are confronted with limited access to established forms of treatment. Acceptance and commitment therapy (ACT) has been found to be an effective extension of cognitive behavioral therapy (CBT) for chronic pain. In this study, we evaluated the ACT-based online therapy program HelloBetter Chronic Pain in a clinical sample of patients with chronic pain in Germany.

Method:

In a randomized, controlled, and investigator-blinded trial, the program was tested against a treatment-as-usual control group (waiting list). HelloBetter Chronic Pain comprises a sequence of seven units with interactive content and audio, video, and textual elements. Written support was delivered by psychotherapists (in training) based on standardized templates incorporating automated components. 360 patients with a medically confirmed diagnosis of chronic pain were included in the trial. The primary endpoint was the degree of pain interference (on the interference scale of the Multidimensional Pain Inventory) at 12 weeks. The efficacy analysis was based on linear regression models (intention to treat [ITT], multiple imputation).

Results:

At 12 weeks, the patients in the intervention group exhibited significantly lower pain interference scores (d = 0.69; 95% confidence interval: [0.46; 0.92]) than those in the control group; they also had fewer depressive symptoms (d = 0.40; [0.17; 0.63]) and experienced better health-related quality of life (d = −0.23; [−0.40; −0.06). These effects were still present at 6 and 12 months.

Conclusion:

HelloBetter Chronic Pain effectively and sustainably reduces impairment by pain to a clinically relevant extent, alleviates symptoms overall, and may contribute to the successful implementation of guideline-based care for patients with chronic pain.

Chronic pain is a common condition (1, 2) and can lead to functional impairments and emotional distress (3, 4). In the primary care setting, the prevalence of chronic pain is about 20% (5–8). Guidelines for the management of chronic pain recommend a multidisciplinary approach to treatment based on the biopsychosocial model (8). Cognitive behavioral therapy (CBT) and its advancement, Acceptance and Commitment Therapy (ACT), are key elements of this strategy (9). ACT-based interventions for treating chronic pain are targeted at reducing pain interference (10), focusing on the need to accept chronic pain in order to minimize functional impairment (11). According to meta-analyses, CBT and ACT achieve small to moderate clinically relevant effects on pain interference in patients with chronic pain (12–14).

Despite the proven effectiveness of the ACT-based approach and recommendations to integrate it into a multimodal therapy concept, affected individuals find that the availability of established forms of treatment remains limited in clinical practice (15–17). The reasons include a shortage of psychotherapeutic resources, long waiting times and limited access (18). Since digital treatment options involve no waiting times, are highly scalable and not limited by time or location, they can overcome these barriers (18, 19). In Germany, doctors and psychotherapists can prescribe and bill digital health applications (DiGA) since 2019. As a result, psychotherapeutic components of multimodal pain treatment are now available to supplement standard care. Meta-analyses revealed small to moderate effects of digital interventions on the degree of pain interference (20–22). A 2016 meta-analysis on web-based therapy programs, including 19 randomized controlled trials (RCTs), found an effect size of Hedge‘s g = 0.41 for chronic pain which is comparable to small to moderate effects of face-to-face interventions (14).

The HelloBetter Chronic Pain online therapy program is based on ACT; with its focus on reducing pain interference, it addresses a key treatment goal in the management of chronic pain. As a DiGA, HelloBetter Chronic Pain can be integrated into a multimodal pain management strategy as an additional treatment option and complement key components of guideline-compliant patient care with low-threshold psychotherapy-based pain therapy. The program builds on the ACTonPain intervention, whose efficacy was evaluated in a randomized controlled trial (N = 302) against a waiting-list control group (23). For the guided version, a significant decrease in pain-related impairment was observed both immediately after the intervention and at six months (Cohen’s d = 0.58; Number Needed to Treat [NNT] = 3.14). For the unguided version, no significant effect was found (p = 0.09). While differences between the two versions did not reach statistical significance, patients in the guided group completed more modules and dropped out less frequently. The DiGA can be used within the treatment-as-usual framework of the German statutory health insurance (SHI) system:

  • as a stand-alone therapy

  • for the secondary prevention of comorbid conditions

  • for tertiary prevention

  • for bridging waiting times (for example, for psychotherapy)

  • as a component of multimodal pain therapy

  • for therapy support.

The aim of this trial was to evaluate the efficacy of HelloBetter Chronic Pain in patients with a medically confirmed diagnosis of chronic pain within the framework of the German healthcare system. Since its approval as a digital health application, doctors and psychotherapists can prescribe the program, the costs of which are covered by statutory health insurance. In this trial, we evaluated for the first time the use of a digital health application in routine care for chronic pain in Germany and expanded our understanding of digital treatment methods by including a clinical sample of patients diagnosed with pain disorders according to the International Classification of Diseases (ICD-10).

Methods

Study design

We designed this efficacy trial (DRKS00027176) as a two-arm RCT with parallel design and waiting list control. Based on a meta-analysis, the sample size was calculated assuming an intergroup effect with a standardized mean difference (SMD) of 0.32 for the primary endpoint (13). A total of 360 participants were randomly assigned to either the intervention group (IG) with direct access to HelloBetter Chronic Pain or the control group (CG). Patients in both trial groups had unrestricted access to treatment-as-usual (TAU) care, including family physician and pain specialist care, psychotherapy, pharmacotherapy, physical therapy, and exercise therapy. Upon request, patients in the control group were granted access to the program after the post time point. The trial was approved by the Ethics Committee of the Technical University of Munich (591/21-S-SR).

Population

From January 2022 to August 2022, people with chronic pain and a confirmed pain-related diagnosis were recruited nationwide in Germany through specialists, newspaper ads, patient support groups, and social media. Confirmed pain-related diagnoses included:

  • Persistent somatoform pain disorder [F45.40]

  • Chronic pain disorder with somatic and psychological factors [F45.41]

  • Chronic back pain [M54]

  • Fibromyalgia [M79.7]

  • Chronic intractable pain [R52.1]

  • Other chronic pain [R52.2]).

The inclusion and exclusion criteria, including confirmation of diagnosis, were assessed in the initial screening (see the eSupplement for further information). Endpoints were assessed using online questionnaires at baseline, at the post time point (12 weeks after randomization), and at 6 and 12 months (follow-ups). Since participants in the control group were granted access to the program at 12 weeks, both follow-ups were uncontrolled.

Intervention

The HelloBetter Chronic Pain program comprises seven weekly course units, each of 45–60 minutes duration, incorporating texts, videos, audio recordings, and exercises (eSupplement). The program is a stand-alone software and a medical device in risk class I according to Rule 11 of EU Medical Device Regulation 2017/745 (MDR).

For risk management reasons, written support is provided by licensed psychotherapists or psychotherapists in training (eSupplement) to participants in the program. The supporting psychotherapists used standardized templates and automated components (e.g., email reminders), supervised the progress of the participants, and, in the event of a crisis or worsening of symptoms, directed patients to services offering treatment as usual.

Endpoints of the trial

The trial’s primary endpoint was pain interference, operationalized using the interference scale of the West Haven-Yale Multidimensional Pain Inventory (MPI), measured at 12 weeks (24, 25). The pain interference scale of the MPI comprises nine items rated on a 7-point scale, ranging from 0 (“no interference/change”) to 6 (“extreme interference/change”), thus resulting in total scores between 0 and 54. Confirmatory secondary end-points included emotional functioning, operationalized via depressive symptoms measured by the Patient Health Questionnaire-9 (PHQ-9) (26, 27), as well as health-related quality of life, operationalized via the Assessment of Quality of Life (AQoL-8D) instrument (28, 29).

In addition, the following explorative secondary end-points were assessed:

  • Impact of pain (West Haven-Yale Multidimensional Pain Inventory [MPI]) (24, 25)

  • Pain intensity and interference (Brief Pain Inventory [BPI]) (30, 31)

  • Pain interference in daily living (Pain Disability Index [PDI]) (32, 33)

  • Anxiety (Generalized Anxiety Disorder Scale-7 [GAD-7]) (34, 35)

  • Pain processing (FESV, German pain processing questionnaire [Fragebogen zur Erfassung der Schmerzverarbeitung]) (36)

  • Pain Acceptance (Chronic Pain Acceptance Questionnaire [CPAQ]) (37, 38)

  • Psychological flexibility (AAQ-II Acceptance and Action Questionnaire, German version [Fragebogen zu Akzeptanz und Handeln II] (39)

  • Psychological Inflexibility in Pain Scale [PIPS]) (40, e1)

  • Pain-specific self-efficacy (Pain Self-Efficacy Questionnaire [PSEQ]) (e2, e3).

More information on the assessment of the endpoints and other additionally measured variables is provided in the eSupplement.

Randomization

We used stratified block randomization (1:1) with variable, randomly assigned block sizes to achieve an even distribution of the diagnostic groups (eSupplement). An independent researcher generated the randomization lists using the Randlist software (Datinf GmbH, Tübingen, Germany; www.randomisation.net).

Statistical analyses

The statistical analyses were performed using the R software (version 4.2.2) and conducted and reported in accordance with the Consolidated Standards of Reporting Trials (CONSORT) statement (e4) (eConsort checklist). The significance level was set at α = 0.05 (two-tailed). Hierarchical hypothesis testing was conducted for the primary endpoint and the confirmatory secondary end-points in accordance with guidelines on the testing of multiple endpoints (e5, e6) (eSupplement). The primary efficacy analysis was based on the intention-to-treat (ITT) principle; missing data were estimated using multiple imputation with m = 50 imputation sets (e7, e8) (eSupplement).

The effect of the intervention was assessed using linear regression models, adjusting for baseline symptoms and the covariate “diagnosis group”. Effect sizes are reported as standardized mean differences (Cohen’s d) (e9). In addition, response rates were calculated for the primary endpoint (reliable symptom change according to the Reliable Change Index [RCI], reliable and clinically significant change, relative change of >30%; eSupplement).

Robustness of the results was assessed using sensitivity analyses (per-protocol analysis, study completer analysis, and analysis using reference-based multiple imputation) (eSupplement).

Analyses performed on the exploratory endpoints were also descriptive. As no adjustment was made for multiple testing, the calculated p-values were purely descriptive and were not used to assess statistical significance.

The proportion of participants with reliable worsening of pain interference was calculated based on the RCI and compared between groups using the chi-square test. Descriptive analyses were performed on data related to negative effects (Negative Effects Questionnaire [NEQ]) (e10), satisfaction (Client Satisfaction Questionnaire, German version [CSQ-8]) (e11, e12) and subjective change (Patients’ Global Impression of Change [PGIC]) (e13).

Results

A total of 1163 persons signed up and completed the initial screening. A total of 360 persons met all inclusion criteria and no exclusion criteria and were included in the trial (IG: n = 178; CG: n = 182; [Figure 1]). The mean age was 49.17 years (standard deviation [SD] = 11.56); 85.8% (n = 309/360) were female (Table 1) (For additional sociodemographic characteristics, refer to the eSupplement).

Figure 1. Flowchart - Efficacy analysis based on the intention-to-treat principle (ITT).

Figure 1

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IG, intervention group; CG, control group

Table 1. Sociodemographic and clinical characteristics of the participants.

Characteristics All (n = 360) IG (n = 178) CG (n = 182)
Sociodemographic characteristics
Age, mean (SD) 49.17 (11.56) 48.57 (11.45) 49.76 (11.67)
Gender: female, n (%) 309 (85.8) 157 (88.2) 152 (83.5)
Working, n (%)
 No 169 (46.9) 85 (47.8) 84 (46.2)
 Yes 138 (38.3) 69 (38.8) 69 (37.9)
 Yes, but currently on sick leave 53 (14.7) 24 (13.5) 29 (15.9)
Diagnosis according to ICD-10, n (%)
Persistent somatoform pain disorder (F45.40) 17 (4.7) 9 (5.1) 8 (4.4)
Chronic pain disorder with somatic and psychological factors (F45.41) 88 (24.4) 44 (24.7) 44 (24.2)
Back pain (M54) 48 (13.3) 23 (12.9) 25 (13.7)
Fibromyalgia (M79.7) 173 (48.1) 85 (47.8) 88 (48.4)
Chronic intractable pain (R52.1) 8 (2.2) 4 (2.2) 4 (2.2)
Other chronic pain (R52.2) 26 (7.2) 13 (7.3) 13 (7.1)
Utilization
Psychotherapy, n (%) 146 (40.6) 77 (43.3) 69 (37.9)
Medication, (pain-relevant and prescription-only) n (%) 223 (61.9) 114 (64.0) 109 (59.9)
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CG, control group; IG, intervention group; SD, standard deviation; ICD-10, International Classification of Diseases, 10th revision

At the post time point, participants had completed an average of 4.72 (SD = 2.68) of the 7 course units; 48.9% (n = 87/178) completed the entire online therapy program; 60.1% (n = 107/178) completed at least five units.

Descriptive statistics for all endpoints are presented in the eTable and mean differences within the study groups in eSupplement Table 7.

eTable. Descriptive statistics for all endpoints.

Baseline Post time point
MCG(SD) MIG(SD) MCG(SD) MIG(SD)
Primary endpoint
 Pain interference (MPI) 4.25 (0.94) 4.31 (0.94) 4.00 (1.01) 3.39 (1.17)
Confirmatory secondary endpoints
 Emotional functioning (PHQ-9) 14.49 (4.79) 15.09 (4.64) 13.58 (4.82) 12.06 (4.86)
 Health-related quality of life (AQoL-8D) 53.70 (11.27) 52.22 (12.13) 54.82 (12.10) 56.26 (12.33)
Exploratory secondary endpoints
Impact of pain (MPI)
 Pain intensity 4.08 (0.89) 4.07 (0.82) 3.86 (0.93) 3.56 (1.02)
 Life control 2.87 (1.09) 2.70 (1.10) 3.15 (1.02) 3.17 (1.04)
 Affective distress 3.52 (1.18) 3.67 (1.13) 3.31 (1.16) 3.10 (1.14)
Pain intensity and interference (BPI)
 Total scale BPI 5.81 (1.75) 5.85 (1.76) 5.52 (1.85) 4.81 (1.82)
Interference of pain with daily activities (PDI)
 Total scale 38.35 (12.32) 38.11 (13.66) 36.95 (13.19) 32.28 (14.10)
Anxiety (GAD-7)
 Total scale GAD-7 9.52 (4.38) 9.83 (4.79) 9.02 (4.81) 8.60 (4.27)
Pain processing (FESV)
 Action-planning competencies 12.99 (5.00) 12.55 (4.64) 13.90 (4.84) 16.16 (3.77)
 Cognitive restructuring 12.29 (4.82) 11.13 (4.51) 11.93 (4.75) 14.61 (4.29)
 Experience of competence 12.26 (4.44) 11.44 (4.34) 12.67 (4.52) 14.33 (4.23)
 Mental distraction 10.52 (3.96) 9.86 (3.88) 10.33 (3.66) 10.99 (4.22)
 Counteracting activities 9.87 (4.22) 9.61 (4.18) 9.99 (4.17) 10.39 (4.28)
 Rest and relaxation techniques 11.20 (5.03) 10.47 (4.39) 11.15 (4.70) 14.01 (4.50)
 Pain-related helplessness and depression 19.81 (6.21) 19.90 (6.16) 18.95 (6.13) 16.68 (5.67)
 Pain-related anxiety 14.04 (5.14) 14.20 (5.39) 13.72 (5.30) 11.83 (4.53)
 Pain-related anger 15.14 (6.84) 15.23 (6.51) 15.08 (6.74) 13.68 (5.83)
Pain acceptance (CPAQ)
 Total scale CPAQ 49.71 (15.58) 48.34 (17.67) 51.41 (15.97) 58.75 (15.86)
 Activity willingness 27.70 (9.85) 26.67 (11.22) 28.16 (10.16) 32.45 (10.28)
 Pain willingness 22.02 (8.63) 21.67 (8.68) 23.25 (8.14) 26.30 (7.70)
Psychological flexibility (AAQ-II)
 Total scale AAQ-II 26.48 (9.07) 27.73 (10.01) 26.58 (9.24) 24.62 (8.62)
Psychological flexibility (PIPS)
 Total scale PIPS 55.68 (10.98) 55.68 (11.65) 53.50 (10.92) 47.35 (10.73)
 Pain avoidance 35.42 (8.69) 35.25 (8.66) 33.94 (8.26) 29.74 (8.21)
 Cognitive fusion with pain 20.26 (4.17) 20.43 (4.27) 19.55 (4.11) 17.60 (4.32)
Pain-specific self-efficacy (PSEQ)
 Total scale PSEQ 29.81 (12.43) 26.59 (12.49) 30.59 (12.43) 33.84 (11.87)
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Where questionnaires report both total scores and subscale scores (CPAQ, PIPS), both the total score and the subscale scores are reported.

For the following instruments, higher values indicate better results: AQoL-8D, subscale of MPI (life control); subscales of FESV (action planning competencies, cognitive restructuring, experience of competence, mental distraction, counteracting activities, rest and relaxation techniques), CPAQ, PSEQ.

M, mean; SD, standard deviation; CG, control group; IG, intervention group; MPI, Multidimensional Pain Inventory;

PHQ-9, Patient Health Questionnaire-9; AQoL-8D, Assessment of Quality of Life 8-Dimension; BPI, Brief Pain Inventory; PDI, Pain Disability Index; GAD-7, Generalized Anxiety Disorder Scale-7; FESV, German Pain Processing Questionnaire;

CPAQ, Chronic Pain Acceptance Questionnaire; AAQ-II, Acceptance and Action Questionnaire-II (German version); PIPS, Psychological Inflexibility in Pain Scale; PSEQ, Pain Self-Efficacy Questionnaire

In the intervention group, the degree of pain interference decreased by 0.91 scale points from baseline to the post time point (95% confidence interval [CI]: [0.66; 1.17]; dwithin = 0.92; 95% CI: [0.67; 1.18]), and in the control group by 0.25 scale points (95% CI: [0.04; 0.45]; dwithin = 0.34; 95% CI: [0.06; 0.62]). At the post time point, the degree of pain interference in the intervention group was 0.65 points lower compared to the control group (95% CI: [0.44; 0.86]). The regression analysis confirmed a significant difference between the groups (t = 5.95, p<0.001; d = 0.69; 95% CI: [0.46; 0.92]; Figure 2).

Figure 2. Raincloud plot.

Figure 2

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(combined box, violin and scatter plot) of key findings for the primary endpoint

Combined graphical representation of the distribution of central tendency and dispersion

Left: Scatter plot (each individual observation); Center: Box plot (central tendency [median and interquartile range]);

Right: Violin plot/density plot (probability density)

With regard to the confirmatory secondary endpoints, the intervention group showed significantly higher emotional functioning at the post time point (t = 3.38, p = 0.002 [Holm-Bonferroni corrected]; d = 0.40, 95% CI: [0.17; 0.63]) and a better health-related quality of life (t = -2.65; p = 0.008 [Holm-Bonferroni corrected]; d = -0.23, 95% CI: [-0.40; -0.06]).

Descriptive advantages were found for the intervention group in all exploratory secondary endpoints except for life control, anxiety, and pain processing (counteracting activities). In addition, Table 2 lists intergroup effects, regression analyses and sensitivity analyses, which confirm the robustness of the ITT results for the primary endpoint (Details can be found in the eSupplement).

Table 2. Between-group effect sizes and findings of the regression analysis.

MD [95% CI] d [95% CI] t p
Primary endpoint
Pain interference (MPI) 0.65 [0.44; 0.86] 0.69 [0.46; 0.92] 5.95 <0.001
Sensitivity analyses
Per-protocol analysis 0.74 [0.54; 0.94] 0.79 [0.58; 1.01] 7.33 <0.001
Completer analysis 0.56 [0.37; 0.75] 0.60 [0.39; 0.80] 5.75 <0.001
Analysis with reference-based imputation 0.49 [0.33; 0.66] 0.53 [0.35; 0.70] − <0.001
Confirmatory secondary endpoints
Emotional functioning (PHQ-9) 1.88 [0.79; 2.98] 0.40 [0.17; 0.63] 3.38 0.002*
Health-related quality of life (AQoL-8D) −2.68 [−4.66; −0.69] −0.23 [−0.40; −0.06] −2.65 0.008*
Exploratory secondary endpoints
Pain experience (MPI)
 Pain intensity 0.29 [0.07; 0.52] 0.34 [0.08; 0.61] 2.56 0.011
 Life control −0.08 [−0.34; 0.17] −0.08 [−0.31; 0.16] −0.63 0.527
 Affective distress 0.29 [0.04; 0.54] 0.25 [0.04; 0.47] 2.31 0.021
Pain intensity and interference (BPI)
 Total scale 0.73 [0.34; 1.11] 0.41 [0.20; 0.63] 3.74 <0.001
Pain interference with daily activities (PDI)
 Total scale 4.47 [1.88; 7.06] 0.34 [0.14; 0.54] 3.39 <0.001
Anxiety (GAD-7)
 Total scale 0.62 [−0.25; 1.50] 0.14 [−0.05; 0.33] 1.40 0.162
Pain processing (FESV)
 Action planning −2.49 [−3.37; −1.61] −0.52 [−0.70; −0.33] −5.54 <0.001
 Cognitive restructuring −3.32 [−4.30; −2.35] −0.71 [−0.92; −0.50] −6.67 <0.001
 Experience of competence −2.15 [−3.06; −1.23] −0.49 [−0.70; −0.28] −4.61 <0.001
 Mental distraction −1.08 [−1.92; −0.24] −0.28 [−0.49;−0.06] −2.54 0.011
 Counteracting activities −0.57 [−1.42; 0.28] −0.14 [−0.34; 0.07] −1.31 0.189
 Relaxation techniques −3.32 [−4.31; −2.32] −0.70 [−0.91; −0.49] −6.54 <0.001
 Pain-related helplessness and depression 2.31 [1.01; 3.60] 0.37 [0.16; 0.58] 3.50 <0.001
 Pain-related anxiety 1.98 [0.95; 3.01] 0.38 [0.18; 0.57] 3.77 <0.001
 Pain-related anger 1.46 [0.16; 2.76] 0.22 [0.02; 0.41] 2.20 0.028
Pain acceptance (CPAQ)
 Total scale −8.22 [−11.34; −5.11] −0.49 [−0.68; −0.31] −5.19 <0.001
 Activity willingness −4.96 [−7.01; −2.90] −0.47 [−0.66; −0.27] −4.74 <0.001
 Pain willingness −3.23 [−4.84; −1.62] −0.37 [−0.56; −0.19] −3.93 <0.001
Psychological flexibility (AAQ-II)
 Total scale 2.86 [1.34; 4.38] 0.30 [0.14; 0.46] 3.69 <0.001
Psychological flexibility (PIPS)
 Total scale 6.14 [3.83; 8.44] 0.54 [0.34; 0.75] 5.24 <0.001
 Pain avoidance 4.08 [2.32; 5.83] 0.47 [0.27; 0.67] 4.57 <0.001
 Cognitive fusion with pain 2.06 [1.15; 2.96] 0.49 [0.27; 0.70] 4.46 <0.001
Pain-specific self-efficacy (PSEQ)
 Total scale −5.51 [−7.89; −3.13] −0.44 [−0.63; −0.25] −4.55 <0.001
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*

p-values are adjusted for multiple testing (Holm-Bonferroni correction)

For the following instruments, higher values indicate a better outcome, and thus negative mean differences/effect sizes indicate a better expression of the endpoint in the i ntervention group compared to the control group: AQoL-8D, subscale of MPI (life control), subscales of FESV (action-planning competencies, cognitive restructuring, experience of competence, mental distraction, counteracting activities, rest and relaxation techniques), CPAQ, PSEQ. As is common in studies on digital psychological interventions, women were overrepresented in the sample (85.8%), potentially limiting the generalizability of the results to men. MD, mean difference; CI, confidence interval; d, Cohen’s d; MPI, Multidimensional Pain Inventory; PHQ-9, Patient Health Questionnaire-9; AQoL-8D, Assessment of Quality of Life 8-Dimension; BPI, Brief Pain Inventory; PDI, Pain Disability Index; GAD-7, Generalized Anxiety Disorder Scale-7; FESV, German Pain Processing Questionnaire; CPAQ, Chronic Pain Acceptance Questionnaire; AAQ-II, Acceptance and Action Questionnaire-II (German version); PIPS, Psychological Inflexibility in Pain Scale; PSEQ, Pain Self-Efficacy Questionnaire

At the post time point, more participants in the intervention group showed improvements on the MPI interference scale: reliable improvement (RCI; IG: 43.8%; CG: 14.8%; χ2(1) = 31.16; p<0.001), reliable and clinically significant change (IG: 37.6%; CG: 13.7%; χ2(1) = 24.84, p<0.001) as well as >30% (IG: 32.6%; CG: 6.6%; χ2(1) = 31.43, p<0.001).

The response analyses are presented in Table 3 and described in detail in the eSupplement.

Table 3. Response analyses.

IG (%) CG (%) X2 p NNT [95% CI]
Reliable symptom change according to RCI
 Worsening 5 (2.8) 10 (5.5) − − − −
 No change 95 (53.4) 145 (79.7) 31.16 <0.001 3.45 [2.64; 4.99]
 Improvement 78 (43.8) 27 (14.8)
Reliable and clinically significant symptom improvement
 No 111 (62.4) 157 (86.3) 24.84 <0.001 4.18 [3.07; 6.58]
 Yes 67 (37.6) 25 (13.7)
Reliable symptom improvement (>30% improvement)
 No 120 (67.4) 170 (93.4) 31.43 <0.001 3.85 [2.96; 5.49]
 Yes 58 (32.6) 12 (6.6)
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CG, control group; IG, intervention group; NNT, Number Needed to Treat; CI, confidence interval; RCI, Reliable Change Index

The subgroup analyses by diagnostic group are based on imputed data and presented in the eSupplement. In all subgroups, descriptively lower pain interference scores were noted in the intervention group at the post time point. Additional analyses on psychotherapy and medication are presented in the eSupplement. Effects were observed both without (d = 0.69; 95% CI: [0.34; 0.97]) and in addition to pain medication (d = 0.68; 95% CI: [0.38; 1.03]), as well as without (d = 0.61; 95% CI: [0.33; 0.89]) and with concomitant psychotherapy (d = 0.76; 95% CI: [0.38; 1.14]). Baseline differences with regard to current treatments (Table 1) are the result of randomization .

Analysis of long-term effects

In the intervention group, the effects of the intervention persisted at 6 and 12 months. In the control group too, substantial improvements were noted at 12 weeks after receiving the intervention (eSupplement). Of all control group participants with follow-up, 75.8% had taken part in the program after the post time point. Comprehensive information on the long-term results for all secondary endpoints is provided in the eSupplement.

Negative effects and satisfaction with the program

No cases of suicidal tendencies, suicidal acts or deaths were noted. Except for the usual side effects, no serious adverse events were reported; 43.0% (58/135) of the patients in the intervention group reported at least one negative effect that they attributed to the program. The level of satisfaction with treatment (CSQ-8) was high: 83.7% (113/135) were satisfied overall (“very satisfied“ or “mostly satisfied“), 88.1% (119/135) would recommend the program to others (“definite yes“ or “yes, I think so“). Participants completed a mean of 4.72 (SD = 2.68) out of 7 course units; 48.9% (97/178) completed the program in full, 60.1% (107/178) at least five units.

Findings on negative effects, satisfaction with treatment and overall subjective assessment of change are presented in the eSupplement.

Discussion

This trial demonstrates the efficacy of the HelloBetter Chronic Pain online therapy program compared to a waiting-list control group with unrestricted access to treatment-as-usual care. At the post time point at 12 weeks, a moderate effect size (d = 0.69, according to Cohen [1988]) was found with regard to pain interference (e9). Participants in the intervention group also reported better emotional functioning (d = 0.40) and a higher health-related quality of life (d = -0.23). In addition, a reliable and clinically significant improvement was achieved by more participants in the intervention group (37.6%; n = 67/178) compared to participants in the control group (13.7%; n = 25/182) (e14). Exploratory effects were observed with regard to other pain-related endpoints and measures of general health.

The effect size found in our trial is larger than the effect sizes from meta-analyses on the efficacy of CBT and ACT in reducing pain interference in chronic pain patients (SMD = 0.18 to 0.44) (12–14). The effect size is also above the SMD of 0.32 (95% CI: [0.19; 0.45]), which was identified in a Cochrane review (13) on pain interference and prespecified as the threshold for assessing clinical relevance. Furthermore, the effects observed in our trial are larger compared to other online interventions designed to treat chronic pain, which showed small to moderate effects on pain interference (SMD = 0.28–0.42) (20–22). Comparability of effect sizes may be limited due to the use of different measurement instruments (for example, only partial use of MPI) (eSupplement). It should, however, be noted that the effect sizes were larger than in studies that also used the MPI as a measurement instrument.

Limitations

One limitation of our trial is the lack of blinding of the participants to their treatment assignment. Given the nature of psychological interventions, effective blinding of participants is difficult to achieve (e15).

The use of a waiting-list control group with access to TAU is a further limitation, as such an approach could lead to both an overestimation of the specific effects due to expectation effects in the intervention group and an underestimation of the effects due to regression to the mean in the control group. Still, the magnitude of the effects is comparable to that found in studies with similar designs on established forms of therapy, such as cognitive behavioral therapy, which makes the clinical relevance of the results seem plausible given the current body of evidence.

Conclusion

The findings of our trial indicate that the HelloBetter Chronic Pain online therapy program can effectively and persistently reduce pain interference in people with chronic pain compared to the control group. The intervention substantially improved the participants’ symptoms overall with regard to further relevant measures of pain-related and general health. In view of the high burden posed by chronic pain (3, 4), the effects of the program should be considered relevant both clinically and in terms of societal impact. Digital therapy programs have the potential to improve patient care by providing psychotherapy-based pain therapy and to overcome barriers to accessing face-to-face psychotherapy.

Acknowledgement

We would like to thank everyone who contributed to the success of our trial. Our special thanks go to Dr. Luisa Balzus, Vanessa Franke, Dr. Anja Zimmer, Hannah Keller, Gesine Schrade, Annika Montag, Sam Goetjes, Amanda Keller, Johanna Mahns, Marvin Franke, Dr. Victor Stephani, Mathias Harrer, and Christina Schulte. Their strong support, expert suggestions, commitment, and dedication have been instrumental in making this work possible.

Footnotes

Conflict of interest: MG supported the development of the evaluation concept for the inclusion of HelloBetter Chronic Pain in the DiGA directory. The University Hospital Bonn received a fee for this service from the GET.ON Institute for Online Health Training GmbH/HelloBetter. MG received grants from the Federal Ministry of Education and Research (BMBF) and fees from CompuGroup Medical.

HB received consulting fees and fees for lectures and workshops as well as license fees for the HelloBetter Chronic Pain online intervention.

MF, EH, DDE, and AE are employed by GET.ON Institute for Online Health Training GmbH/HelloBetter. DDE and EH are shareholders of GET.ON Institute for Online Health Training GmbH.

DDE received grants from EU H2020, DFG, Innovation Fund, health insurances, and BMBF. He served as a consultant or member of the scientific advisory boards of Sanofi, Novartis, Minddistrict, Lantern, Schoen Kliniken, and German health insurances (BARMER, Techniker Krankenkasse, Ideamed). DDE received fees for workshops from German Boards of Psychotherapists and was a member of the board of the German Psychological Society (DGPs) and President of the International Society for Research on Internet Interventions.

AB was a member of the Data Safety Monitoring Board (DSMB) of the trial.

Data availability

In cases of legitimate scientific interest, anonymized trial data may be requested from the first author AE, citing the relevant research project.

Supplementary material

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References (abbreviated)

Associated Data

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

Data Availability Statement

In cases of legitimate scientific interest, anonymized trial data may be requested from the first author AE, citing the relevant research project.

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