Depression is one of the most common mental health–related diagnoses worldwide [1]. It causes debilitating psychological pain, problems in one’s social life, and loss of productivity to individuals who have it. Furthermore, the hopelessness that many patients with depression feel is linked to suicidal behavior [2]. For many individuals, depression has a recurring trajectory over the life span, and each recurrent episode increases the likelihood of development of later episodes [3]. Beyond the hardships that individuals go through, depression also imposes a considerable burden on health care systems worldwide as the psychological and pharmaceutical treatments for depression are costly [4].

Cognitive behavioral therapy (CBT) is an effective and well-researched psychotherapy approach with extensive evidence on its effectiveness in the treatment of a wide range of mental health disorders, including major depression and dysthymia [5-7]. Especially for the treatment of depression, CBT has been shown to provide superior treatment outcomes compared with alternative psychotherapy methods [8]. In CBT, a high degree of adherence to the therapy is key to a successful treatment process and long-term outcomes. Insufficient engagement with therapeutic resources (especially between sessions) and dropouts from psychotherapy because of poor engagement are potential hazards for patients that may impair its effectiveness [9]. Research shows that patients’ adherence to assigned homework within their treatment program—especially behaviorally demanding assignments—is considerably low [10,11]. According to therapists, more than half of patients face difficulties in completing their homework as prescribed, which in some cases leads to considerable negative consequences for therapy outcomes [12]. In contrast, there is a wealth of evidence that homework compliance is a significant predictor of better treatment outcomes [13-16]. Given these circumstances, it is not surprising that relapse and recurrence rates are high in CBT treatments. For example, a meta-analysis addressing relapse and recurrence rates following CBT programs for depression reported that relapse and recurrence rates can be as high as 46.5% throughout the treatment and highly predicted by residual depressive symptoms after the completion of therapy [17].

To alleviate these problems and support patients in CBT adherence, scholars have proposed to leverage the advantages of internet-based CBT (iCBT) in conventional face-to-face CBT treatment plans [18]. iCBT treatment options consist of web-based platforms offered to patients for use through smartphones or computers that provide them with psychoeducational content and homework tasks digitally [19]. By integrating an iCBT app and face-to-face CBT treatment into the same treatment protocol, a blended CBT (bCBT) modality offers a new treatment method that aims to incorporate the merits of both [20]. Although it promotes patient autonomy and makes psychotherapy easily accessible outside the therapy sessions, bCBT still preserves personal contact with a therapist and recognizes the therapeutic relationship as an important factor in treatment success [21]. bCBT programs have been suggested to intensify the therapy process by making it easier to record a patient’s activities and thoughts, review the content of the therapy between sessions, and organize homework. Organizing homework in particular leads patients to focus on completion and enhances learning as a result [22]. bCBT programs also promise to reduce the total therapy duration [23,24].

Although there is no consensus in the literature on a single taxonomy for bCBT programs [18,25,26], bCBT treatments have primarily been categorized as either sequential or simultaneous according to how the face-to-face and digital components of blended therapy are introduced and scheduled [18]. In sequential bCBT treatments, patients’ individual work with a digital mental health app either precedes or follows the face-to-face treatment with a psychotherapist [18]. Stepped care approaches could exemplify sequential blended treatments [27,28]. Simultaneous bCBT programs offer face-to-face and digital elements within the same period [18], oftentimes in the form of working on therapeutic homework through the digital app between face-to-face sessions with a therapist [29,30]. Our focus in this study is on simultaneous bCBT treatment as we believe this approach has the greatest potential to efficiently achieve positive long-term therapy goals.

Several studies have confirmed the additional benefits of simultaneous bCBT compared with face-to-face therapy in alleviating depression symptoms and mental health–related burdens on patients [18,25,29,31-33], whereas there are also studies where patient mental health outcomes in bCBT conditions were found to be similar to usual treatment [21,34-36]. Important is that none of those studies found that bCBT resulted in worse mental health outcomes. Similarly, some studies find bCBT to be a more cost-effective alternative to standard CBT [24,34,37], whereas others find longer total treatment time and higher costs in bCBT conditions when the amount of therapist contact remains constant [21,38]. More research is needed to shed light on these various outcome findings. The bCBT programs in these studies face shortcomings as they are rarely developed as a unique synthesis of the digital app and face-to-face therapy but simply use them simultaneously as distinct or adjunct therapy elements [29,39]. As an alternative to adjunct programs, more personalized and interconnected digital and face-to-face elements would offer an integrated bCBT program [25,30].

To overcome the obstacles associated with conventional CBT programs and leverage the advantages that bCBT programs promise, understanding the demands and requirements of an integrated bCBT program is essential. Accordingly, this study aimed to discover patients’ and therapists’ attitudes and expectations from digital mental health apps to develop better-integrated bCBT protocols. Existing knowledge on how to design an efficient digital mental health app for a bCBT protocol is heavily based on qualitative data collected during pilot studies of newly developed apps [30,40,41]. Unlike those studies, this research aimed to collect input from patients and therapists who were naive in bCBT programs, which means that they were not currently receiving a bCBT treatment and were not introduced to any bCBT app for the goals of the research. Principally, we also assumed that they had no previous experience with a bCBT program as integration of digital health apps in the psychological health care system is new in Germany and there were no bCBT options at the time of data collection or earlier [42,43]. As a result, we were able to identify the needs and expectations of patients and therapists from a perspective of inexperience with bCBT programs. Such an approach would also allow us to discover if patients and therapists have different user needs in the digital working spaces within a mental health app. Developers of new apps in this field would thereby have a general perspective on the needs of users rather than user reflections guided (and directly influenced) by previous interactions with already extant platforms.

We designed this explorative study to this end. The following research questions were addressed: (1) What are therapists’ and patients’ attitudes toward integrating digital interventions into conventional face-to-face CBT? What are the expected benefits? What are their concerns? (2) Do patients and therapists have different needs or attitudes regarding digital apps? (3) How do these attitudes and needs (including differences) translate into features of a digital mental health or software app?

We used a qualitative research design for this study. Qualitative methods are especially suitable for studies based on explorative research as these methods enable deriving direct insights from this study without presuppositions from earlier research [44,45]. We conducted semistructured interviews with both CBT-oriented psychotherapists and patients who were in psychotherapeutic treatment at the time of the study to unravel the perspectives of both sides of a therapeutic relationship. We deliberately targeted a patient sample with depression as the advantages of bCBT over face-to-face therapy appear most evident in this patient population [25,29,33,34]. Patients and therapists were given an explanatory introduction to the concept of bCBT programs to ensure a common understanding of the target topic of inquiry before the interviews took place. In these interactions, we made clear that our focus was on simultaneous bCBT protocols that present digital apps within the same period as face-to-face treatment [18]. We communicated that our goal would ultimately be to develop a digital app based on and incorporating the participants’ feedback.

The study was approved by the Ethical Board of the University of Mannheim (EK Mannheim 38/2020). Interviews were conducted by coauthor MS, who is experienced as an interviewer and has conducted several qualitative studies in the past focused on digitalization and product development. There was no relationship between the interviewer and participants before this study. Interviews with participants were conducted between February 2021 and May 2021. Participants did not receive any monetary compensation for taking part.

The transcripts and meeting notes from the interviews were coded according to grounded theory, a systematic data analysis methodology that focuses on inductively developing abstract theoretical conceptions from empirical data [46,47]. For the coding of transcriptions, Dedoose software (version 8.0.35; SocioCultural Research Consultants) for qualitative research was used. Patient and therapist interviews were coded separately and each interview independently. First, patient interviews were coded. Then, therapist interviews were coded. As a result of qualitative analysis of patient interviews, 4 main categories (expected features of bCBT apps, expected qualities of bCBT apps, qualities to avoid in bCBT apps, and concerns regarding bCBT apps) and several subcategories within these main categories were formed by inductive category formation based on the content of the interviews and codes assigned to text passages within them. Similarly, based on therapist interviews, 5 main categories (day of a therapist, attitudes toward digital apps, expected features of bCBT apps, expected qualities of bCBT apps, and concerns regarding app integration into therapy) and several subcategories within these main categories were formed inductively. We iterated between the developing model and the data until a viable set of first-order codes, second-order themes, and aggregate dimensions was identified, stopping when we reached “theoretical saturation” [48]. A joint agreement was reached among all authors to stop recruitment when saturation was achieved. The coding procedure was conducted by multiple researchers to ensure intercoder reliability—EA completed the first round of coding the data, and MS reviewed the coding scheme. A second coding round was then performed by EA and MS. Subsequently, the coding scheme was reviewed again by EA, MS, and JAH, and some adaptations were discussed. Finally, JAH approved the categories. As there were only minor adaptations that emerged from cross-checking, 2 coding rounds were considered sufficient. The completed COREQ (Consolidated Criteria for Reporting Qualitative Research) [49] checklist can be found in Multimedia Appendix 1. The interview quotes included in this paper were translated by a professional translator from German into English.

Our study explored patients’ and psychotherapists’ attitudes toward the introduction of a digital mental health app into their ongoing psychotherapy process, including their expected features and concerns regarding bCBT protocols. We gained valuable insights into the perspectives of both potential user groups. Both patients and therapists had positive attitudes toward bCBT and digital health apps in general. The results provide not only a rich frame of reference regarding what functions are expected from an integrated digital app but also a guide on what to avoid.

We suggest that this qualitative study is an important contribution to the relevant literature as scientific inquiry into how to construct a digital app for bCBT protocols has not been extensive enough to create a solid framework [26]. Current knowledge is mostly based on interview data with patients or therapists regarding their personal experiences with existing bCBT programs combined with initial evaluations of programs that have been developed [30,40,41]. Our study alternatively offers fruitful data on patient and therapist experiences and expectancies that were not guided by any particular digital program. As patients and therapists in our study were not actively using a bCBT program and were assumed to lack experience with such programs given that these were not available earlier [43] (and no sample intervention was provided), they were not oriented toward a specific existing digital health program while voicing their views on potentially helpful and unhelpful digital program features. In conducting such an exploration without focusing on a particular digital health app, our study resonates with the work by van der Vaart et al [50], although their study used survey questions and qualitative data in parallel. A similar methodological approach to ours was used in the qualitative investigation by Cerga-Pashoja et al [51], but they conducted their exploration only with therapists. With this study, those who wish to develop integrated blended solutions for existing problems in psychotherapy can find the voices of both patients and therapists regarding potential problems and practical solutions. To our knowledge, the explicit distinction between adjunct and integrated digital app designs in bCBT programs has not been made earlier in the literature. On the basis of studies on existing digital apps calling themselves as such [29,30], we pointed out this distinction and showed in this study that an integrated bCBT design is more desirable to potential users.

In this study, patients and therapists mostly agreed on which functions would be expected in a digital app, and the differences were few but notable. Data security proved to be one of the fundamental issues that therapists needed assurance about, whereas patients were not as concerned. Conversely, patients saw potential negative connotations attached to the prescription of a digital mental health program, whereas therapists did not. These findings inform researchers and developers working in the field of digital mental health apps on how different functional aspects were viewed positively or negatively and underline how psychotherapy is experienced differently by patients and therapists.

Our findings are in line with the existing consensus in the bCBT literature on the need for customizability of digital apps to an individual patient’s needs in terms of both content and use [26,41,50]. Both therapists and patients view the rigidity and nonexclusiveness of existing digital tools as the reasons for their current limited use [52]. Our study supports these findings. Similarly, references to a desire for high usability in a digital program were made by both therapists and patients, supporting an earlier study with therapists pointing to “intuitive usability and logical structure of online platform” as a facilitator of bCBT use [41]. Attempts to develop new digital mental health programs or modify existing ones should address these concerns.

Aside from simply replicating the findings on the need for personalization, we argued that there could be 2 different interpretations of what personalization of a digital program means. According to one interpretation of the data, different patients should not be given identical psychological intervention content or feedback, which is consistent with previous research [26,41,50,53,54]. A second interpretation suggests that some patients view any restricted means for personal expression as a feature to avoid (as in the example of smiley faces or multiple-choice questions). Patients reported that these methods were inadequate to their communication needs. To our knowledge, this call for more open-ended and expressive means of recording one’s mood and symptom history as well as personal thoughts is a new interpretation of customization in the digital mental health domain.

Previous findings on the needs of patients and therapists within the context of bCBT programs agreed that digital apps should avoid overwhelming patients [40,51]. For example, the volume of homework exercises delivered through the digital app [40] and the reminders and notifications provided [51] should not be excessive. Our findings endorse these earlier studies. Similarly, our findings supported the findings of van der Vaart et al [50] that therapists are concerned about preserving boundaries and keeping in-person therapy sessions central. Our study suggests that face-to-face and web-based elements should focus on distinct goals within a bCBT protocol, with the latter concentrating on the practical aspects of the therapy (such as homework assignments, diaries, and psychoeducation), whereas process-related matters and evaluation of the patient’s condition are reserved for face-to-face meetings with the therapist [50]. Therapists had differing views on the potential effect of digital mental health apps on the therapeutic relationship between a patient and a therapist, with some suggesting that treatment through bCBT protocols may foster this relationship, whereas others expressed skepticism. Remarkably, none of the therapists thought that digital mental health apps would hinder the relationship between patient and therapist. These findings are important considering that the therapeutic relationship is known to be one of the strongest predictors of treatment success [55-57].

Receiving extra assistance in a bCBT treatment was put forth as an important potential benefit by both patients and therapists in our interviews. Given that both patients and therapists are eager to try a digital app to promote their therapy progress, digital apps appear to offer a practical solution to widespread adherence issues regarding patients completing assigned homework [10,12].

As our patient sample included only those who were diagnosed with depression and was small (n=11), the needs and expectations of this patient group might not be generalizable to all patients in psychotherapy. Patients with different mental health diagnoses might have different needs and express them differently than the population we studied. Moreover, our study included a selective sample of adult patients who were already undergoing CBT-oriented therapy and were seemingly motivated and held positive attitudes regarding bCBT programs. Patients who are not yet in treatment for their symptoms, such as those on waiting lists, or those who are not receiving a first-line treatment such as CBT might hold different views from those of our sample. Similarly, we cannot make claims about the potential of bCBT programs in children and teenagers with our findings as we deliberately targeted only adult patients. Further research is needed to understand if and in what conditions nonadult users can benefit from bCBT programs. For some patients, careful evaluation of their suitability for a bCBT program might be necessary. For instance, based on our finding that therapists believe it is crucial to ensure that digital app use does not lead to excessive use of digital devices and potential addiction as a result, patients who are prone to technology addiction may need higher caution before a bCBT program is introduced to them.

A limitation of our study is that we did not ask patients about their current or previous involvement with stand-alone iCBT programs or other digital apps. Differential familiarity with such programs might potentially influence user views. Furthermore, we did not record how long participating patients had been in psychotherapy. Different experiences in terms of completed therapy duration might have led to differing opinions of patients. In contrast, examining patient views independent of the duration they had spent in therapy could also be considered a strength because, as we did not set any patient duration in therapy as an inclusion criterion, our study potentially covers a higher variety of patients. Finally, the explicit distinction we made between adjunct and integrated bCBT programs was mainly based on our observations in the literature. More research is needed to support the validity of such a clear conceptual distinction.

Our therapist sample consisted of only those working with a CBT orientation and was small (n=23). It should be noted that previous research has showed that therapists who work with a CBT orientation have more positive attitudes toward the idea of using digital and blended interventions in the context of psychotherapy compared with therapists using other psychotherapy orientations [58,59]. Thus, the results of this study might not be generalizable to all psychotherapists regardless of their therapy orientations.

All patients and therapists participating in this study resided in or close to Cologne, Germany. Hence, one cannot directly generalize findings to other cultures or other regions of Germany.

Further research is needed to investigate expectations and opinions of different patient samples as well as comparisons of participant expectations of various psychotherapy approaches.

Our qualitative study found that patients and therapists who had never participated in a bCBT program could imagine themselves using one. They were willing to incorporate a digital app into their current face-to-face therapy practices. Both parties in the therapy relationship were open and curious about the possibilities and opportunities that technology could bring to their treatment journey. Participants provided a detailed framework for what features should be included in digital apps, independent of any particular mental health app introduced to them before the study. Therefore, researchers and developers of new technological solutions can use our findings as an independent guide when constructing new digital apps.