Introduction

Depression in its clinical and subclinical manifestations is a highly prevalent condition (Cuijpers et al., 2004). Since access to psychological treatments is often difficult for affected individuals (Kohn et al., 2004), internet interventions for depression have been developed to overcome some of the barriers limiting the access to treatment (e.g., a shortage of trained professionals, waiting lists, costs and stigma, Cuijpers, 1997) and, furthermore, to deliver accessible and scalable treatment options. Stand-alone self-help interventions, a type of internet therapy delivered without guidance of a therapist, are especially cost-effective and scalable (Blanck et al., 2018). They are highly structured and standardized and usually comprise several modules containing information and exercises. There is strong evidence from meta-analyses on randomized-controlled trials that unguided internet interventions for depression are efficacious with small to moderate effect sizes (e.g., Anderson & Cuijpers, 2009; Reins et al., 2021; Richards & Richardson, 2012).

Most of the unguided internet interventions for depression utilize cognitive-behavioral (CBT) approaches (Schröder et al., 2016). While these CBT interventions were consistently shown to be effective, developing more diverse approaches to the internet treatment of depression could be useful. Effect sizes of unguided internet interventions are in the small to moderate range and adding treatment elements with a different therapeutic focus might increase their effects. Moreover, developing different interventions with more diverse treatment principles gives individuals more options to choose a preferred type of intervention. Since treatment preference is a moderator of treatment outcome (Swift et al., 2018), giving individuals a choice between different effective treatments might increase the overall effect of internet intervention for depression.

One promising target for the treatment of depression might be the human body. During the past two decades, basic research has shown that motoric and emotional processes are interrelated in non-clinical as well as in clinical populations. A large number of studies have investigated the effects of emotional processes on the motor system (e.g., posture, facial expression) and, importantly, vice versa in non-clinical individuals. Meta-analytic aggregations of various studies have shown that motor displays affect a broad range of emotional processes like affective responses and overt behavioral responses (Elkjær et al., 2022a; Körner et al., 2022).

Moreover, a number of studies on depressed individuals have found evidence that the motor system might also be relevant in this clinical condition. A recent meta-analysis (Elkjær et al., 2022b), including 71 studies, found differences in motoric parameters between healthy and clinical (depression and anxiety) groups (g = 0.26). Most studies in the field of depression investigated gait speed and other gait parameters. Moreover, Elkjær and colleagues also conducted a narrative review of experimental studies investigating the effects of short motor manipulations within clinical groups. They reported that four out of five studies found significant effects of motor system manipulation on affective outcomes. For example, Michalak et al. (2018) asked depressed individuals to perform one of two different Qi Gong movements. Qi Gong is an element of traditional Chinese mind–body medicine incorporating orchestrated body postures and movements, breathing practices and meditation (a more detailed description of Qi Gong is given below). One movement sequence was an upward-opening Qi Gong practice, which runs counter the slumped and downward movement pattern usually observed in depressed individuals (e.g., Michalak et al., 2009). The other movement sequence was also a regular Qi Gong practice but its downward-closing style did not run counter the habitual depressed movement pattern (see Video 1 for the upward-opening movement sequence; Video 2 for the downward-closing movement sequence; https://www.uni-wh.de/gesundheit/department-fuer-psychologie/lehrstuehle-und-professuren-psychologie/lehrstuhl-fuer-klinische-psychologie-und-psychotherapie-ii/). During these two different movement sequences, patients were presented 10 positive and 10 negative cue words. Their task was to respond to each word with an autobiographical event that the word reminded them of. The event should be specific in the sense that it happened at a particular place and time and lasted for a day or less. After the movement sequences stopped, an incidental recall of the cue word was conducted. The results showed that patients practicing a downward-closing Qi Gong movement showed the typical negative memory bias of remembering more negative words than positive words, while patients practicing an upward-opening Qi Gong movement recalled a significantly higher proportion of positive items. Thus, the movement had effects on the negative memory bias typically observed in depressed individuals (Matt et al., 1992). Moreover, the upward-opening group produced more specific autobiographic memories than the downward-closing group. Thus, in addition to effects on negative memory bias, the Qi Gong movement affected another important characteristic of depressed memory: the tendency to report unspecific autobiographic memory (Williams et al., 2007).

The experimental study of Michalak and colleagues (2018) has shown that a short Qi Gong practice, lasting for 11–13 min, can have short-term effects on dysfunctional memory processes that are relevant in the aetiology of depression. Other research has investigated the effects of more extensive Qi Gong training programs on depressed patients’ psychopathology. Two reviews and meta-analyses aggregated evidence of Qi Gong-based therapy for depression. Guo et al. (2019) included seven randomized controlled trials (RCTs) on Qi Gong therapy for adults diagnosed with Major Depressive Disorders, Liu et al. (2015) included 18 RCTs with Qi Gong as a treatment for individuals with depressive symptoms. Both meta-analyses indicated that Qi Gong appears to have beneficial effects on depression. However, authors of both meta-analyses stress that the results have to be interpreted with caution since many of the included studies had low methodical quality.

In addition to this preliminary evidence from RCTs on the effects of Qi Gong interventions, there are several other arguments for the possible utility of Qi Gong as a treatment component for depression. Qi Gong encompasses a variety of different practices including movements, breathing practices and imagination. Movements can be targeted to the specific bodily alterations of depressed individuals. For example, upward-opening movements can be used to counteract negative effects of the habitual slumped and downward movements of depressed individuals and to realign posture and movement patterns. Therefore, Qi Gong might have effects beyond the well-known general positive effects of physical activity on depression (Imboden et al., 2021; Pearce et al., 2022). Moreover, Qi Gong movements are usually carried out with a mindful focus on the body. This embodied mindfulness might assist participants to step out of dysfunctional ruminative states of mind and reconnect with the lived experience of the present moment (Farb et al., 2012; Khoury et al., 2017). Moreover, there is preliminary evidence that depression is associated with dysfunctional breathing patterns (Zamoscik et al., 2020). Therefore, the Qi Gong breathing practices aiming to train healthy breathing patterns might have beneficial effects on depression. In addition, intrusive mental images are very common in depression and these intrusions are related to strong emotions (Görgen et al., 2015; Patel et al., 2007). Rescripting negative mental imagery can be effective in the treatment of depression (Moritz et al., 2018). Therefore, training individuals to form positive mental images, which is another core Qi Gong practice, might be another beneficial element in Qi Gong treatment of depression. Another speculative line of reasoning for the potential utility of Qi Gong practice is that it might address a core phenomenological feature of depression, the loss of energy and vitality (DSM-5: MDD criterion A5; American Psychiatric Association, 2013). Phenomenological studies claim that loss of vitality is at least as important for the subjective experience of depression as depressed mood (Fuchs, 2013). The term ‘Qi’ in Qi Gong can be translated as 'vital energy', ‘Gong’ as ‘cultivation’ or ‘work’. Although more research is certainly needed on the phenomenology and actual “energy cultivating” effect of Qi Gong, Qi Gong aims, at least by its own admission, to influence phenomenologically important aspects of the subjective experience of depression (e.g. loss of vitality).

Inspired by empirical evidence from basic and clinical research on the effects of short-term motor manipulations on emotional processes, by the preliminary evidence of the efficacy of in-person Qi Gong training for depression and by the potential utility of various components of Qi Gong practice for the treatment of depressive symptoms, we developed Body, Breath, and Mind (BBM). BBM is a minimally monitored internet intervention for the treatment of depressive symptoms that combines Qi Gong and behavioral activation (BA). This combination seems especially promising because BA is equally effective as other psychotherapies for depression (Dimidjian et al., 2006; Jacobson et al., 1996; Richards et al., 2017), but less complex (Ekers et al., 2011). This feature makes it specifically suitable for an internet intervention (Furukawa et al., 2021). Moreover, the value-based types of behavioral activation that assist participants to clarify personally relevant values and to formulate behavioral goals in the direction of these values might, besides the general increase of activation, help participants to orient their mind in a value-based and healthy direction. In summary, the goal of BBM is to address the body by movement-oriented Qi Gong exercises, the breath by breathing Qi Gong exercises and the mind by value-based behavioral activation. Therefore, BBM tackles three important and interrelated ‘layers’ of the human existence to strengthen vitality and treat depressive symptoms (see Fig. 1).

Fig. 1
figure 1

Targets of Body, Breath & Mind

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The aim of our present research was to explore the feasibility, acceptability, adherence, and preliminary outcomes of this new 8-module BBM internet intervention in a sample of participants with elevated levels of depressive symptoms. We examined participant feedback to the overall program and to individual Qi Gong and behavioral activation components, with the perspective to evaluate BBM in a future RCT, if it is found to be acceptable and feasible. We hypothesized, that this program would be acceptable to participants and lead to significant reductions in depressive symptoms.

Methods

Participants and Design

The participant flow diagram is shown in Fig. 2. Participants were recruited via university news release, social media and self-help forums. Inclusion criteria were at least moderate depressive symptoms (i.e. Patient Health Questionnaire, PHQ-9, score ≥ 10, Kroenke et al., 2001), legal age, sufficient language level and access to internet and e-mail. Participants with high psychomotor agitation or suicidality (criteria A5 and A9 for major depression, DSM-5, American Psychiatric Association, 2013) were excluded from participation, since the activating treatment components of BBM and the minimal therapeutic support would probably not meet their needs. Exclusion criteria were assessed via phone, using the German version of the Structured Clinical Interview for DSM-IV (SKID-I, Wittchen et al., 1997). Informed written consent was obtained from all participants. The study was approved by the local ethics committee (number of ethic approval: S-18/2021). Participants were informed that they could contact the study team via email/chat if any problems or negative events emerged during BBM. In this case, the procedure was as follows: the PI (J.M.) contacts the participant, clarifies the severity and potential causality of an (serious) adverse event in relation to the intervention, assists the participant to seek medical or psychological support and documents the event.

Fig. 2
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Participant flow chart

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The participants included in our study were on average M = 44.34 (SD = 12.69) years old, mostly female (85%, n = 93), and most had a high school diploma (71%, n = 76). With regard to their relationships, 26% (n = 29) were single, 20% (n = 22) had firm partnership, 44% (n = 48) were married and 10% (n = 11) divorced/widowed. Participants had, on average, a moderate level of depression at baseline (M = 14.25, SD = 2.83).

Body, Breath and Mind

BBM is an online intervention that aims to reduce depressive symptoms. It combines Qi Gong elements with value-oriented behavioral activation (BA; Dimidjian et al., 2008; Jacobson et al., 2001; Martell et al., 2001, 2010). In eight modules, an advanced Qi Gong teacher guides through mindful Qi Gong movement, breathing, relaxation, and imagination exercises. All modules (for an overview of module procedure see Fig. 3) started with a video with J.M. and T.P. that shortly introduced the Qi Gong and BA elements of the modules (for an overview of exercises see Table 1). The choice of Qi Gong exercises included in BBM was based on findings from research on embodiment in depression presented above. For example, lifting and opening movements, in contrast to the habitual slumped posture, were trained (modules 2, 3, 7), exercises to regulate breathing (modules 2, 4) and generally activating Qi Gong exercises (module 1) were included. In addition, Qi Gong exercises to strengthen self- and other compassion (Gilbert, 2010) by embodied friendliness (i.e., smiling to towards oneself and towards the surroundings) were introduced (modules 5, 6).

Fig. 3
figure 3

Procedure of Body, Breath & Mind modules. BA Behavior activation

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Table 1 Body, Breath & Mind – module overview and satisfaction ratings
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Moreover, Qi Gong exercises chosen for BBM were inspired by ideas of traditional Chinese medicine (TCM) about causes of depression (Maciocia, 2009). It should be noted, that in TCM depression is not understood as a unified disease, but rather as different psychosomatic disharmonies, which can cause different disorders, that are, in western nosological systems like the DSM-5 or ICD, subsumed under the umbrella term ‘depression’. TCM developed interventions like acupuncture, herb therapy or Qi Gong to specifically address psychosomatic disharmonies. The Qi Gong exercises included in our program focused on the different disharmonies supposed to be associated with depression in TCM (see Table 1).

In each module, a video, with detailed instructions on the exercise(s) newly introduced in the module, is presented (for a detailed description of BBM Qi Gong exercises see supplement 1). The instructions lasted approximately 5–10 min (for an overview of Qi Gong exercises introduced in the modules, see Table 1). After that, a practice video is shown (length: approximately 30 min). The participants use this video to practice the new Qi Gong exercise(s) with the Qi Gong teacher. In modules 2 to 8, before the introduction to the new exercise(s), a video is presented with in-depth instructions to review the exercise from the last module. Then, a video is shown in which the exercise(s) from the last module are practiced (approximately 10 min). General instructions for useful principles when practicing Qi Gong (e.g., helpfulness of regular daily Qi Gong practice of approximately 30 min, the importance of patience and trust, dealing with physical and psychological limitations) are presented in module one. Moreover, participants can access an optional extra module specifically developed for dealing with problems during the BBM course (e.g., lack of motivation, physical difficulties) in all eight modules.

Videos were embedded within the modules. In addition, six videos for everyday practice between the modules were separately provided every week. For each day of the week one of two exercises were recommended for practice: the exercise that was newly learned and the exercise from last week's module.

After the Qi Gong part of the module (i.e., repetition of the exercise from the last module and practice of the new exercise) the BA module theme and the BA exercise were presented (for an overview, see Table 1). The BA themes were interwoven with important principles of the Qi Gong. For example, in module 4 participants are told that Qi Gong exercises and value-oriented activities can promote each other. If through the Qi Gong exercises they gradually learn to realize a good degree of physical activation in their everyday life and if they change an unfavorable, slumped posture, then this can also give them more energy for the implementation of value-oriented activities. And vice versa, if they carry out more activities in their everyday life that correspond to their values, it will also help them to feel more vital on a physical level. Furthermore, in module 7, the idea was introduced that Qi Gong exercises can help participants to reduce rumination. If they practice Qi Gong regularly, and strengthen the mindful “connection” with the body, it will be easier for them in everyday life to direct attention from their head into their body and also to "connect" more with their surroundings (e.g., nature).

The BA elements contain psychoeducation, identification of one’s own values, planning and implementing value-based activities, strategies for dealing with difficulties in implementing activities, mindfulness and strategies for dealing with rumination and for relapse prevention. These BA are elements regularly included in BA interventions (e.g., Hofheinz et al., 2017; Jacobson et al., 2001; Martell et al., 2001, 2010). They were presented mainly in text-based format with audio-instructions in some modules (e.g., 5- and 20-min versions of mindfulness practice in module 6).

Time to complete an entire module, including Qi Gong exercises and BA elements, takes one to two hours. Participants could decide whether they want to work on the entire module all in one go or step by step.

BBM was implemented on the platform Minddistrict (https://www.minddistrict.com). Participants could contact team members (graduate students in psychology, supervised by J.M.) in case of technical problems or when they had questions concerning Qi Gong or BA elements. This function was used by 30% of participants. On average, responses by team members took no more than 10 min. Correspondingly, the total time spent for administration per participant was less than 3 min.

Outcomes

Depressive Symptoms

In each module, we assessed participants’ depression symptoms with the Patient Health Questionnaire (PHQ-9, German version by Löwe et al., 2003). With 9 items, the PHQ-9 scores each of the DSM A-criteria of major depression on a scale for 0 “not at all” to 3 “nearly every day” (e.g. “I feel down, depressed, or hopeless”). Studies have shown that the PHQ-9 shows high reliability (Cronbach’s α between 0.88 and 0.89) and validity (Kroenke et al., 2001).

Participant Satisfaction

From the second module onwards, participants were invited to retrospectively evaluate the previous module. They separately evaluated the Qi Gong exercise and the BA element (scale: 0 “not helpful at all”, 1 “only partly helpful”, 2 “somewhat helpful”, 3 “very helpful”, 4 “extremely helpful”). Moreover, after module 8 participants evaluated the entire program retrospectively with the ‘Questionnaire to measure patient satisfaction’ (QMPS; Schmidt et al., 1989). The original version of the QMPS comprises 8 items (e.g., “Did the treatment you received help you to deal more appropriately with your problems?”, “Overall, how satisfied are you with the program you received?”) and was developed to assess satisfaction with psychiatric treatment in a clinic. For the present purpose, one item that had a reference to the clinic setting was adapted for the online program, and one item that had a reference to the clinic setting was removed. Participants rated their satisfaction on a scale form 0 “quite dissatisfied” to 3 “very satisfied”, accordingly the total scores can range between 0 und 21. The 7-item version of the QMPS had internal consistency of α = 0.94 in the present study.

Practice Time

We assessed Qi Gong practice time retrospectively at the start of each module with two items: ‘How many days a week on average (considered the past 7 days) did you practice Qi Gong exercises?’ (scale: 0–7 days), ‘How many minutes a day on average (considered over the past 7 days) did you perform the Qi Gong exercise?’ (minutes a day).

Statistical Analysis

The overall attrition rate across the eight measurements was 69% loss in participation. Of the maximum possible assessment points (110 participants × 8 modules = 880) participants responded to 491 (55.8%). To address the resulting missing data, we used mixed-effects models to substitute and analyze the data (Chakraborty & Gu, 2019). Based on maximum-likelihood estimation, these methods use all available data, take into account the dependency of measurements within persons, and have been found to result in less biased coefficients in the presence of missing data than data other methods (Olsen et al., 2012; Salim et al., 2008). To analyze individual changes in depression, we used mixed models/multilevel analysis (Bolger & Laurenceau, 2013). It was tested whether progression in the intervention would predict depression symptom severity. In addition to this multi-level approach, we complemented our analyses with more conservative ways of assessing pre-post changes and computed effect sizes with last observation carried forward-, per-protocol (i.e., participants completing at least four modules) and completer analysis (i.e. participants completing all modules).

Moreover, we descriptively analyzed data on participants’ adherence, satisfaction and practice frequency/time.

Results

Adherence

Figure 2 shows adherence to the BBM program. One hundred and ten participants completed module 1. The entire program with eight modules was completed by 34 participants (31%), 60 (55%) participants completed four or more modules. Participants completing all eight modules did not differ significantly from non-completers in baseline PHQ-9 scores, sex ratio and education. However, we found significant difference in age (t[108] = 3.63, p < 0.001), completers were older (M = 50.56 years, SD = 11.01) than non-completers (M = 41.55 years, SD = 12.46), and family status (χ2 = 4.24, df = 4, p < 0.05), completers less likely had a firm partnership and were more likely divorced/widowed.

Reduction of Depressive Symptom Severity

At baseline, participants (N = 110) had, on average, a PHQ- 9 score of M = 14.25 (SD = 2.83).

We analyzed the individual change in depression using hierarchical multi-level regression analysis with depression levels repeatedly measured within persons. We conducted an initial random intercept model, which indicated that with an intra-class correlation of 0.37, a considerable amount of variance in the PHQ-9 scores can be attributed to between-person differences. Progression in the intervention from the first to the last module was conceptualized as time variable. Stepwise χ2 tests confirmed that including time, squared time, random intercepts and random slopes for time contributed to variance explanation and were therefore kept in the final model. Time (F[1, 366.45] = 88.89, p < 0.001) and squared time (F[1, 190.20] = 28.84, p < 0.001) significantly predicted depression symptom severity. On average, to participate in one module reduced the PHQ-9 score by 1.87 due to a linear trend and increased it by 0.15 due to quadratic trend. The latter indicates attenuation of symptom improvement with program progression.

The multilevel analysis predicted an average PHQ-9 score of M = 8.67 (SD = 2.88) for the measurement after module 8. Since most participants completed around four modules, that score corresponds to the reduction of approximately two units in the PHQ-9 due to each completed module (but also includes random effects). The effect size of pre-post symptom reduction resulting from the mixed model was dAV = – 1.82, using averaged standard deviations (Cumming, 2012).

In addition to this effect size estimate based on mixed model approach we computed effect sizes using last observation carried forward: dAV = – 0.98 (N = 110); per-protocol analysis dAV = – 1.42 (at least four modules, N = 60), and completer analysis dAV = – 2.1 (N = 34).

None of the participants reported an adverse or negative event.

Satisfaction

Overall satisfaction rating assessed with the QMPS at post-treatment was M = 16.29 (SD = 4.42) (representing a mean item score of 2.33 [SD = 0.63] on a scale from 0 to 3), indicating a high satisfaction with BBM. Looking at individual items of the QMPS, 35.3% (n = 12/34) of participants completing the program were ‘largely satisfied’, 52.9% ‘very satisfied’ (n = 18/34) with the program. Regarding the question of whether they would recommend the program to a friend, 26.5% (n = 9/34) of participants completing the program rated ‘I think yes’, 61.8% ‘unequivocally yes’ (n = 21/34). Moreover, regarding the question ‘Did the program you received help you deal more appropriately with your problems?’ 50.0% (n = 17/34) of completers rated ‘Yes, it helped a bit’, 41.2% (n = 14/34) ‘Yes, it helped a whole lot.’

In addition to overall satisfaction ratings at post-treatment, at the beginning of each module we asked participants to retrospectively rate the satisfaction with Qi Gong exercises and BA elements introduced in the last module (see Table 1). The Qi Gong satisfaction ratings ranged between 1.90 (SD = 1.01) (module 4: ‘Intonating the Ha-sound’) and 2.57 (SD = 0.91) (module 3: ‘Lift, open, lower, close’ in an activating style), representing ratings between ‘somewhat helpful’ and ‘very helpful’. No Qi Gong exercise was rated in the range of not being helpful. Ratings of BA elements ranged between 2.15 (SD = 0.86) (module 2: development of an individualized model of maintaining factors, module 2) to 2.50 (SD = 0.86) (module 7: ‘rumination as a hindrance’), again representing ratings between ‘somewhat helpful’ and ‘very helpful’, with no BA element rated as not helpful.

Practice

Weekly Qi Gong practice frequency and time are shown in Table 2. Participants practiced between 4.12 (week 1) and 3.43 (week 4) days a week and between 18.60 min and 16.88 min a day. This means that participants, on average, practiced slightly more than half of the recommended Qi Gong practice time (7 days per week; 30 min per day).

Table 2 Weekly Qi Gong practice frequency and time
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Discussion

The present study investigated the feasibility of BBM, a minimally monitored internet intervention for depressive symptoms combining Qi Gong and behavioral activation. Feasibility outcomes included adherence, a preliminary assessment of the program’s effectiveness, satisfaction with BBM and practice time.

Our results indicate that BBM might effectively reduce depressive symptoms. In our analysis we found an uncontrolled pre-post effect size for the reduction of depressive symptoms of dAV = – 1.82 based on a mixed-model approach. Although, maximum-likelihood estimations that use all available data have been found to result in less biased coefficients in the presence of missing data than completer analysis and last observation carried forward (Olsen et al., 2012; Salim et al., 2008), we decided to additionally use these alternative methods to calculate effect sizes. Last observation carried forward analysis, the most conservative method, yielded an effect size of dAV = – 0.98, representing a large effect. Completer analysis, as an estimate of the upper bound of effects of BBM, yielded a very large effect of dAV = – 2.1.

All effect sizes we obtained were large and higher than the effect sizes reported in meta-analyses of computer-based psychological treatments for depression (Richards & Richardson, 2012; Schröder et al., 2016). Of course, the pre-post effect size in our study is not directly comparable to post-treatment between-group effect sizes reported in meta-analyses. Pre-post effect sizes tend to overestimate change attributable to the intervention, because of regression to the mean and spontaneous remission. As an estimate of spontaneous remission, Tong et al. (2023) have shown that even waitlist control conditions in randomized controlled trials of digital-based psychological intervention yielded effects of g =  − 0.29. Moreover, the percentage of missing data was high which might have biased our estimate of the effect size derived by the hierarchical multi-level regression analysis.

Another limitation is the overrepresentation of participants with high education level. Over 70% of our sample had a high school diploma. While overrepresentation of higher educated individuals is a common limitation of studies on internet interventions (Späth et al., 2017), future research should clarify whether this limitation might be intensified in treatment approaches that integrate principles stemming from Asian meditation traditions (Carlson, 2018). If so, measures should be taken to increase diversity by developing recruitment strategies targeting the needs and preferences of individuals with lower education level (e.g. by describing treatment principles more in accordance with mental health models of this subgroup and addressing their limited time and financial resources).

Keeping these limitations in mind, the reduction of depression severity we found nevertheless seems to make BBM a promising intervention for further more rigorous tests of effectiveness.

Satisfaction ratings indicate that the program was acceptable for participants. Qi Gong practices and BA elements were rated, on average, between ‘somewhat helpful’ and ‘very helpful’. No Qi Gong or BA element was, on average, rated as not being helpful. However, there were some variations in the satisfaction ratings of the Qi Gong elements. There seems to be a trend that especially the Qi Gong exercises including gentle forms of breathing practices (i.e., nourishing breathing, intonating the Ha-sound) showed less favorable satisfaction ratings. It can be speculated that, because breathing patterns are distorted in depressed individuals (Zamoscik et al., 2020), it might be especially challenging for participants to regulate their breath during the gentle breathing exercises of BBM.

In addition to satisfaction ratings for single BBM elements, post-treatment overall satisfaction with BBM was high and the majority of participants would recommend BBM to a friend. However, it should be noted that satisfaction at post-treatment was only rated by the 31% of participants, who completed all eight modules. It is likely that unsatisfied participants were especially prone to drop out of the program earlier. Therefore, it seems likely that the post-treatment satisfaction assessment is, to some degree, positively biased. However, the session-based satisfaction rating on Qi Gong and BA do not show a trend for more positive ratings in later modules with a higher percentage of completers, and one can therefore speculate that positive bias of post-treatment satisfaction ratings might not be very strong.

The most important limitation of our study is the high dropout rate of 69%. Dropout rates in online-delivered treatments are influenced by the type of support: for example, Richards and Richardson’s (2012) meta-analysis identified a dropout rate of 74% for unsupported programs, 38% for programs with administrative support, and 28% for programs with therapeutic support. Because participants could contact team members when confronted with difficulties, BBM can be classified as an online program with administrative support. However, it should be noted that administrative support was minimal (on average less than 3 min per participant). Moreover, BBM is a program with relatively high demands: modules were relatively long (one to two hours), some Qi Gong exercises required physical effort and daily homework practice of 30 min were recommended. All of these factors might have affected drop out of depressed individuals in the present BBM study.

Although the effects size varied depending on the methods used to handle drop-outs, even in the most conservative intention-to-treat analysis we found a large reduction in depressive symptoms in study participants. The large effect size for participants, who completed the whole program (d = – 2.1), compared to the smaller intent-to-treat effect size, indicates that a sub-group of people, who adheres to the BBM program, benefits more strongly. Further studies should elucidate patient characteristics predicting adherence to BBM. The larger effect size in the intention-to-treat analysis indicates that even participants, who did not complete all eight modules, benefited from BBM. Nevertheless, in future studies measures to reduce dropout from BBM should be taken into account. Modifications of the program could be considered. For example, exercises or modules with relatively low satisfaction ratings (e.g., ‘nourishing’ breathing in module 2 or intonating the Ha-sound in module 4) could be removed from the program. Moreover, although increasing the costs of the program, regular telephone or videophone coaching might be an option to reduce attrition rates. In addition, more regular prompts to continue the program could be helpful (Titov et al., 2013) or a reduction of module length/content and homework practice recommendations. Moreover, future research could also investigate the potential of blended version of BBM, combining online with face to face interventions (Bielinski et al., 2021). Because of the face to face component, blended versions of BBM could reduce dropout rates and would give the opportunity to provide participants individual feedback on Qi Gong exercises and BA elements.

A methodological limitation of our study was the uncontrolled pre-post-design and lack of follow-up assessment. The design was useful to get a first evaluation of the feasibility of BBM. However, to draw stronger conclusions on the effectiveness of BBM, randomized controlled studies are needed, comparing BBM with waiting list and other (gold-standard) internet interventions. With randomized controlled studies factors like spontaneous remission and regression toward the mean can be controlled. Moreover, our results do not allow inferences on the relative contribution of Qi Gong and BA elements to the effects we observed. Dismantling designs will be necessary to investigate whether adding Qi Gong to a CBT intervention like BA has additive treatment effects. However, even if Qi Gong does not increase the effectiveness of CBT interventions, it could be that some individuals with depression are more attracted to an online intervention targeting the body than to an intervention that solely addresses cognition and behavior. Therefore, BBM could be a useful treatment option even in the case of equal effectiveness compared to other programs because it might widen the scope of online programs giving depressed individuals more choice.

Despite the above noted limitations, the present study provides preliminary evidence for the feasibility of BBM, a program that combines body-oriented Qi Gong interventions rooted in TCM with BA. BBM is an example of a program that was inspired by the idea to combine promising interventions from different cultural backgrounds to treat depression, one of the most prevalent and detrimental condition. Future research has to show whether BBM is an intervention that proves its effectiveness in comparison to empirically well-established internet interventions. If so, a program like BBM, also addressing the embodied nature of depression, could give individuals more options in choosing between different online interventions that suit their individual preferences.