A qualitative longitudinal study was integrated into a monocenter rater blinded RCT (Hahne et al. in process; preregistered at clinicaltrials.gov: NCT04730518), comprising YoGI as an add-on treatment to the regular inpatient treatment as usual (TAU). Participants included in the study were randomly allocated to two groups: the control group received TAU, while the experimental group received YoGI in addition to TAU. Rater-blinded assessments, as well as qualitative semi-structured interviews were completed at baseline (T₀) and at post-intervention (T₁) 4-weeks later (see Figure 1). Participants who received TAU were interviewed as well, at both time points (T₀ and T₁). This allows for a more differentiated comprehension of potential mechanisms at action and possible impacts of YoGI adjunct to the comprehensive standard treatment. Data collection took place between May 2021 and June 2022.

Recruitment of participants took place on the ward for psychotic disorders at Charité –Universitätsmedizin Berlin, Campus Benjamin Franklin. All inpatients were screened and the eligibility to part-take in the study was assessed by a multidisciplinary team in weekly medical rounds. After being informed about the study by the study assistants and expressing willingness to participate, patients were verified according to the following inclusion criteria: (a) diagnosed with a Schizophrenia-Spectrum-Disorder (SSD) (ICD-10: F20–F29) by a qualified psychiatrist, (b) aged between 18 and 75 years, (c) able to communicate effectively in German language, and (d) able to give written consent about their willingness to participate in the study. Exclusion criteria were defined as (a) any neurological disorder, (b) any item rated > 6 on the P-Scale of the PANSS suggesting an acute psychosis with severe psychotic symptoms, (c) acute substance use or substance abuse (except nicotine) according to ICD-10 criteria assessed by a qualified psychiatrist, (d) acute suicidality assessed by a qualified psychiatrist, and (e) contemporaneous co-therapies such as electroconvulsive- or ketamine therapy.

In total, N = 33 participants (n = 19 YoGI+TAU and n = 14 TAU) from the ward for psychotic disorders at the Charité – Universitätsmedizin Berlin were included in the present study. Of these participants, n = 20 participants were diagnosed with schizophrenia (F20), n = 6 with schizoaffective disorder (F25), n = 4 with acute polymorphic psychotic disorder (F23), n = 2 with delusional disorder (F22), and n = 1 with schizotypal personality disorder (F21), all according to ICD-10 criteria. Except for one person (n = 1), all received psychotropic medication. There were no significant differences between both conditions on any demographic and clinical measures at baseline, which is displayed in detail in Table 1. There was a total of n = 5 dropouts (n = 2 YoGI+TAU and n = 3 TAU), all due to premature discharge against medical advice. Therefore, no post-intervention (T₁) interviews could be conducted with these participants.

Treatment as usual (TAU) consisted of the comprehensive standard care inpatient treatment offered at the ward for SSD at the Charité – Universitätsmedizin Berlin. An interdisciplinary team with multiple professionals such as psychiatrists, clinical psychologists, social workers, occupational therapists, physiotherapists, and psychiatric nurses was carrying out the interventions. Each patient received an individualized weekly therapy plan according to official treatment guidelines. The treatment program included pharmacological treatment, individual cognitive behavioral therapy (CBT) once a week and several group therapies such as concentration practice, psychoeducational groups, metacognitive training, self-confidence training, occupational therapy, physiotherapy, and physical exercise.

The 50-min class, as an add-on to TAU, was held weekly by a clinical psychologist and a yoga teacher as a co-therapist, who helped with mental support and hands-on-alignments during the intervention. The class was openly offered to all patients in the in-patient ward, regardless of study participation. Group sizes varied between 3 and 10 participants. YoGI was tailored specifically to patients with SSD. The intervention was based on a semi-structured manual (Table 2). The manual was developed continuously in close collaboration with various psychologists, yoga teachers, as well as the patient’s. The criteria for the asanas selected were that these would be doable for all participants regardless of their physical fitness. The structure of YoGI was supported by preliminary findings of our research team (69, 70). The results of the studies highlight the importance of adaptations to deal with potential challenges and ensure inclusivity. The yoga mats were arranged in a circle so that all participants faced each other as well as the teacher. This was chosen to create a heightened sense of security and to support a group feeling. Props such as blocks, and blankets were provided to assist the performance of the postures. Participants with physical limitations could participate from a chair and were given separate instructions in this case. Following recommendations concerning implementing mindfulness for psychosis, prolonged phases of silence were kept to a minimum and basic anchoring methods were used, as well as comprehensible language (72, 73). Instructions emphasized curiosity about bodily sensations and encouraged participants to find a balance between “ease” and “effort” in relation to their physical engagement in the practice. Therefore, choices to modify postures, to stay in or return to a particular posture, were always offered. YoGI started with an invitation to bring awareness to what is present in that moment. Afterward, there was room for patients to share their intentions or wishes for the upcoming class. The participants were guided through a sequence that included posture sitting, standing, and laying down. The class ended with a deep relaxation savasana, where participants were guided through a brief body scan or listened to relaxing music. Afterward, there was a final round, where they could share about their experience.

Participants’ attendance was documented at each yoga class. All (n = 19) YoGI + TAU participants attended 4/4 yoga sessions.

Rater-blinded assessments were conducted by a resident physician of psychiatric medicine or a licensed psychologist at baseline (T₀). Assessments included three rater-based questionnaires to assess the severity of various clinical symptom dimensions.

The present study collected qualitative data through 61 interviews (YoGI n = 36, TAU n = 25). The interview language was German. A semi-structured interview guideline with open-ended questions was prepared, based on two previous qualitative studies of the research team (69, 70). The interview guide (see Table 3) was created through an iterative process by the researchers involved in this study, including a consultant psychiatrist, a psychotherapist, clinical psychologists, and a sociologist, to assess the content and ensure comprehensible wording. Patient participation was invited during a pilot phase consisting of five interviews. After each interview, feedback on the guideline interview questions was obtained and integrated. All interviews were conducted face-to-face by one interviewer LT, a white, female-identified medical student (6th year) who is a certified yoga teacher and co-instructed the YoGI sessions with IH over a period of 4 months. LT received interview training by KB and LF. The interviews were audio recorded. Questions were asked openly and a detailed response to the question was encouraged.

The baseline interview (T₀) comprised a list of five open-ended questions and lasted between 6 and 39 min (on average 19 min). The post-intervention interview (T₁) contained 12 open-ended questions and took between 6 and 61 min (on average 32 min). The 6-min interviews were conducted with a patient with catatonic symptoms, which complicated her engagement in the conversation. Questions in the baseline interview (T₀) centered around the current mental state of the participants, wishes and goals for the inpatient stay, their motivation regarding the psychotherapeutic treatment options and their prior experience with yoga and mindfulness. The post-intervention interview (T₁) included questions regarding the participants’ overall experience with the psychotherapeutic treatment options, discussing which therapies were found to be particularly helpful and which therapies were not experienced as supportive. Moreover, it was explored what experiences were made during the therapeutic intervention and what was learned during the intervention if regarding a transfer into daily life. Questions emphasized the overall experience of the in- patient stay and participants were asked to talk about their three most favorable therapies. This way of phrasing was intended to minimize the implication that participants were supposed to speak specifically about YoGI, reducing social desirability bias. In light of expressed concerns about a “positivity bias” in mindfulness research (85) (due to researchers’ sympathy for the mindfulness practice and their interest in promoting it), the research design was compiled beforehand to reduce and actively reflect these proclivities (86). In accordance with COREQ guidelines (87) the authors acknowledge the unique relationship between the researcher and the participants, which is especially sensitive in longitudinal qualitative research (88). Participants and researcher LT have been in contact before and after the interview on the ward for psychotic disorders solely for study appointments for YoGI.

To ensure data confidentiality according to “Datenschutz Grundverordnung” (DGSVO) data privacy law, all data was pseudonymized. All electronic data was password protected and stored on secure data servers hosted by the Charité – Universitätsmedizin Berlin. Electronic tablets were used administer quantitative data using the software REDCap which works with encoded connections and manages data in the case reports. Audio recorders and tablets were stored in lockers to which only selected members of the research team had access. The pseudonymous data will be stored for a maximum period of 10 years at Charité – Universitätsmedizin Berlin.

Data was analyzed following inductive Thematic Analysis (89), a well-established method for reporting and analyzing data and describing patterns in detail. As LQR is “not tied to any particular methodology or analytical approach” (88), thematic analysis was chosen, because it is suitable to give voice to the individual’s subjective experience in a longitudinal qualitative study design (88, 90) while offering a structured mode of categorizing the data. Throughout the complete analysis, the researchers engaged in a process of continuous critical reflection on their own preconceived notions and ideas. Therefore, they paid particular attention to the fact that themes do not naturally reside in the data but instead reflect on the active, interpretative, and selective role of researchers within the analytical process (89).

When a case number of 30 participants (n = 50 interviews) was reached, the data analysis began. 11 additional interviews were collected until code and meaning saturation set in (91). From this point onward, data collection and data analysis occurred simultaneously as it is commonly practiced in LQR (92). Data was systematically managed using MAXQDA20, a qualitative analysis software to systematically manage and store data. The following process were conducted:

The study was approved by the local ethical committee of Charité – Universitätsmedizin Berlin, Germany (EA4/239/20) and preregistered at clinicaltrials.gov: NCT04730518. The object of the study was fully explained to the participants and written consent about participation and audiotaping was obtained before the interview. The interviewer LT emphasized the optionality of taking part in the study. Furthermore, the participants were informed of their right to withdraw from the study and stop the interview at any time. Participants were not financially compensated for their participation.

One mechanism of action is based on participants’ reports of reduced distress related to psychotic symptoms due to acquiring competence in relaxation–using various techniques they acquired during YoGI (e.g., breathing exercises, present-moment awareness, detachment, and mindfully moving into yoga postures). These findings are consistent with the qualitative literature on the stress-reducing effect of yoga for SSD (69, 96), as well as for other clinical populations (97–100), highlighting the transdiagnostic effects of yoga practice. The application of these self-regulatory techniques took place not only during YoGI. Participants reported using them spontaneously as flexible coping strategies when dealing with auditory hallucinations, anxiety, rumination, sleep disturbances, and pain during their inpatient stay. The enhanced ability to relax was perceived as a key benefit of YoGI, as the symptoms of SSD are related to and can be exacerbated by stress and anxiety (101, 102).

Furthermore, research suggests that it is not the occurrence of psychotic symptoms itself that leads to a distressing experience, but the individual’s reaction to these symptoms and the associated meaning (103, 104). Therefore, self-regulatory techniques may support more functional management of psychotic symptoms, through both acceptance of their presence and an active engagement with them, leading to desensitization and symptom decline through exposure (105–107).

Our qualitative findings on increased interoceptive awareness as a mechanism of action of YoGI, align with previous qualitative findings stating that yoga practice increases body awareness in non-clinical populations (108), as well as in individuals with schizophrenia (96). Participants of YoGI reported how increased interoceptive awareness and feeling more anchored within their body reduced anxiety, mirroring the mechanisms of MBIs overall in supporting individuals to acknowledge their anxiety. Increased interoceptive awareness also contributes to the ability to identify opportunities to take self-responsible action within the yoga practice (e.g., changing a pose if it causes physical pain or intensifying a stretch if it feels good). Here, a rediscovery of one’s ability to execute behavior occurred: the participants began to feel self-efficacious, and able to make decisions according to their own physical and emotional needs. A qualitative study conducted with adolescents with psychosis conceptualized personal empowerment as “taking control and making decisions for oneself” (109). These findings align with other studies indicating that self-determination and agency play a critical role in the recovery of schizophrenia, as it enables individuals to understand better their health-related needs (109–111).

Obesity is common amongst individuals with SSD (112–115), often leading to dissatisfaction with body image (116). Those study participants with obesity described a reduction of body-related shame, as well as increased self-compassion through experiences of positive embodiment in YoGI, such as being grounded and sensing the body vs. being in the head and focusing on physical deficits and limitations. These outcomes are in line with previous findings that show that yoga practitioners display a more positive body image than non-yoga practitioners (117) elucidating the effects of yoga practice on positive body image and increased self-acceptance as well as -compassion (118–122).

Alongside increased interoceptive awareness, participants in the present study stated how they gained meta-cognitive insights–defined by Flavell as “cognition about cognition” (123)–through connecting external actions (e.g., “I did the child’s pose”) to internal states (“I felt soothed”). Here, the bodily experience functioned as a vehicle for self-knowledge and self-regulation. These findings are in line with a recent systematic review (26) that proposed increased meta-cognitive awareness through mindfulness practice as an underlying mechanism of action for decreasing negative symptoms (124). Increased meta-cognition, as well as a furthered “knowledge about oneself” (125) and the capacity to distinguish oneself as separate from depressive and negative symptoms (e.g., negative thoughts), have shown to be effective in the treatment of SSD (126, 127)

In terms of a pluralistic psychiatric approach, YT could be an effective additional therapeutic option, as it promotes increased self-awareness and as self-efficacy. This could have a synergistic effect, increasing medication adherence, as impaired insight is one of the key drivers of medication non-adherence, contributing to impaired long-term functioning in SSD (128–130). Furthermore, research among patients with post-traumatic stress disorder has shown that yoga practice might promote engagement in psychotherapy (100, 131, 132), suggesting that yoga practice may increase awareness of internal states and strengthens emotional regulation, which occurs before effective engagement in psychotherapy (100, 133). Therefore, simultaneous participation in YT and psychotherapy could lead to better therapeutic outcomes in SSD as well as other psychiatric disorders than either modality alone, as they promote similar effects, such as emotion regulation and developing the capacity for introspection (132). Future studies might examine this relationship more closely by investigating the simultaneous engagement of both therapeutic modalities.

Almost all participants considered the group format of YoGI to be valuable, although the format of YoGI included relatively little time devoted to verbal sharing. The results demonstrate the positive impact of group therapy–as a low-cost and low-threshold treatment modality–for individuals with SSD. The group format promoted feeling connected and receiving mutual support, temporarily easing social isolation and stigma (134, 135). Qualitative studies show that the relationship between instructor and participant, as well as between participants themselves, plays an important role in the successful delivery of MBIs (136). Positive social interaction has been empirically identified as an important recovery factor (137, 138). Participants in YoGI described the normalizing and empowering experience of being addressed as a “fellow human being” and being included for who they are, regardless of mental disorder and/or physical limitations. Previous literature highlights the importance of interpersonal recognition and acceptance for the recovery process in SSD (139–141). Nonetheless, participants continue to deal with social and mental illness-related stigma and exclusion outside of YoGI, impacting their treatment offers, identity and lifestyle. This touches on a limitation of YoGI, as it does not address the social context in which participants live. If limiting social conditions (e.g., high prices for yoga classes, low availability of inclusive, mental-health informed YT) are not considered, it is questionable how sustainable the therapeutic change can be in the long-term, as regular practice might be a key factor in the effectiveness of YT. This highlights the importance of integrating the social conditional aspects in the future development of YTs theory and practice for individuals with SSD.

The main findings within the mechanism of spiritual wellbeing were related to dimensions such as meaning in life, purpose, and hope. Spirituality is empirically linked to lower stress levels (142, 143) and studies suggest that it supports adaptive coping in individuals with mental disorders (144, 145). However, most of the yoga research, ignores the spiritual dimensions of yoga (146–149). Interestingly, despite the secular nature of YoGI, participants responses suggest that even a yoga practice without explicit spiritual teachings can influence aspects of spirituality. In line with previous studies (146, 150–152), the introspective character of the yoga class supported a sense of basic trust, openness, and helped to maintain hope in surviving life’s adversities, such as an acute psychotic episode. The distinction between YoGI and other therapies (such as exercise therapy) also becomes apparent through the analysis of the language used to describe participants experiences. These findings show that there is an emic difference between YoGI and other in-patient therapies, as participants used descriptions like “connecting to the soul” and “inner peace.” Participants narrations point to an important source of hope connected to YoGI: the simple moments in yoga class when participants transcended the here-and-now of their current psychiatric in-patient status and experienced moments of presence and flow. Exploring one’s spirituality may promote a person’s sense of hope for the future by rediscovering what is important to them and, therefore, may facilitate personal recovery (153–156). Participants reports imply that many turned to spirituality to cope with their illness and therefore welcome the therapeutic integration of holistic approaches. These findings are in line with a recent study that suggests the clinical incorporation of spiritual aspects to broaden the spectrum of evidence-based treatments for individuals with mental health conditions (157). The extent to which yoga, due to its comprehensive philosophy, is superior to other body-oriented methods and relaxation techniques (e.g., progressive muscle relaxation) should be further investigated, as empirical findings comparing effectiveness are rare (158).

Before and after the intervention, participants reported having the idea that yoga could help them to cope with their mental disorders, which motivated them to engage in YoGI. However, the provision of YT in an institutionalized context for patients with SSD is scarce. This is likely based on the myth that meditation can induce psychosis (159–162), causing skepticism and reluctance due to safety concerns. This view is held by both treatment providers and individuals with SSD themselves. In general, adverse events are insufficiently emphasized in both psychotherapy (163) and mindfulness research (85). A recent study about adverse events in relation to meditation practice pointed out that participants with pre-existing mental disorders were more likely to report unpleasant experiences as well as higher severity of those experiences, possibly due to strong identification with unpleasant emotions and a reluctancy to let them pass (164). Practicing yoga or meditation may lead to greater awareness of one’s physical sensations, feelings, and thoughts (165), and so subjecting individuals to an increased confrontation with their symptoms.

The current study shows that three out of 19 participants during YoGI experienced an increase in symptoms (e.g., ruminating thoughts, de-realization) or showed other adverse effects, such as anxiety about losing control during yoga practice (e.g., lying on the floor, closing their eyes). The qualitative nature of this study allowed an in-depth analysis of the difficulties arising during yoga practice. Thereby, the results of this study can inform about necessary treatment adaptations. Consistent with trauma-informed yoga protocols (166), strategies for dealing with these adverse phenomena include the yoga teacher’s a non-directive, empowering stance. This includes encouraging participants to modify the practice by offering different variations within the postures. For example, for the final relaxation (savasana), participants can choose to remain in a seated posture, instead of lying down on the floor with closed eyes. The awareness of having a choice can help participants to stay present in their experience and recognize that they are safe, even when uncomfortable sensations or feelings arise. Given the increased risk of adverse experiences, future yoga interventions for individuals with SSD should give more time for spontaneous expression of emotions and concerns so that strategies can be found to work collectively through the difficulties that may arise during practice. Participants of YoGI described didactic and structural aspects of YoGI that they perceived as supportive in regard to yoga practice (see Table 6). Yoga, as a practice that connects a person’s body, mind, and/or spiritual experience, could be a fruitful adjunct treatment for individuals with SSD, as it assists participants in accessing their personal resources. This is consistent with the paradigm shift in therapy for individuals with SSD: from a focus on disability to a focus on empowerment and recovery (155, 167–171).

There are several important strengths and limitations to this study. To the best of the authors’ knowledge, this is the first qualitative longitudinal study evaluating persons with SSD experiences with yoga. Another strength of this study is the inclusion of a control condition, who received TAU, allowing a better distinction between the general effects of the in-patient stay and the specific mechanisms of action and processes of YoGI. Two researchers analyzed the data independently by two researchers to reduce the influence of subjective bias and to strengthen the results’ comprehensibility. Over 1 year of research, findings were regularly discussed within the research team, and thus improving intersubjectivity and the overall quality of the analysis through a stepwise analysis process.

There are also limitations, as qualitative data is inappropriate for determining the impact of the intervention on measurable mental health outcomes. We, therefore, conducted this qualitative study alongside a RCT in which quantitative outcomes of YoGI on multiple dimensions, including symptom representation and cognition, are assessed by displaying a mixed-methods design. This study aimed to investigate YoGI for in-patients who displayed residual symptoms, with chronic symptom representation (mean duration of illness for YoGI: 11.63 and TAU: 18.85 years) and moderate positive and negative symptoms, as well as comorbid depressive symptoms. For a limited period (4 months), the interviewer was involved in conducting YoGI, making the interviews more susceptible to social desirability bias. However, to minimize this effect, interviews did not explicitly inquire about YoGI, but rather asked about the participants’ three favorite therapies at the ward. An important limitation was the availability of a single coder due to cost and time constraints. Results are, however, based on a pretest-posttest design. Therefore, no conclusion can be drawn about the long-term effects of YoGI. Future qualitative longitudinal studies should consequently include follow-up periods of up to 3 or 12 months to capture the long-term effects. The single-center design prevents generalizability of applicability to other inpatient and outpatient settings. In future stages of this and other studies, multicenter designs should be considered.