Effect Sizes of Permanently Listed Digital Health Applications (DiGAs) in Germany
This census of Germany's permanently listed Digital Health Applications (DiGAs) reveals that while the majority of efficacy data is accessible and high-quality, a minority of applications rely on non-peer-reviewed publications with potentially inflated effects and insufficient methodological detail.
Original paper licensed under CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). This is an AI-generated explanation of the paper below. It is not written or endorsed by the authors. For technical accuracy, refer to the original paper. Read full disclaimer
In Germany, a new kind of medical treatment has emerged, one that lives entirely on a smartphone screen. These are digital health applications, officially known as DiGAs, which function as software-based medical devices. Unlike a typical wellness app that anyone can download for free, these tools are prescribed by doctors and paid for by health insurance, just like a pill or a physical therapy session. To earn this status, a developer must prove that their app actually helps patients, a requirement that has led to a unique system where companies can get their products listed quickly while they continue to gather long-term proof. By late 2025, forty-seven of these applications had passed the initial hurdles and received permanent approval, a milestone suggesting they offer real, lasting benefits. However, while the government had approved them, the medical community and the public lacked a clear, unified picture of how well these forty-seven apps actually worked compared to one another.
To fill this gap, researchers at the H.P. Zenner Clinical Research Institute and the University of Tübingen conducted a complete review of every single permanently listed app in the country. They did not sample a few favorites or look at just one type of illness; instead, they gathered every available study report, journal article, and regulatory document for all forty-seven applications. Their goal was to measure the size of the benefit each app provided, using a standard way of comparing results that allows doctors to see if an app offers a small, medium, or large improvement over doing nothing or receiving standard care. They also examined the quality of the evidence behind each app, checking whether the results came from rigorous, peer-reviewed studies or from less formal reports that had not been scrutinized by independent experts.
The investigation revealed a landscape of mixed but generally promising results. For the majority of the apps, the evidence was strong and transparent. Thirty-nine of the forty-seven applications had full reports that had been reviewed by scientific journals or government regulators, providing a solid foundation for their approval. When the researchers calculated the magnitude of the benefits, they found a wide range. Some apps showed very large improvements, particularly those treating sleep disorders, bladder issues, and depression. For instance, one app for sleep disorders showed a benefit so substantial it stood out as the most effective in the entire group. Other apps, particularly those for chronic conditions like multiple sclerosis or personality disorders, showed smaller, though still positive, effects. The typical app in this group provided a moderate level of help, a result that aligns with what is generally seen in digital mental health treatments.
However, the study also uncovered significant gaps in transparency that could not be ignored. Eight of the forty-seven apps relied on evidence that had not undergone formal peer review, meaning their data was either published only as brief summaries or as preliminary drafts. These unreviewed apps reported larger benefits on average than the ones with full, vetted reports, a pattern that often suggests the results might be inflated or that smaller, less reliable studies are being highlighted over larger, more rigorous ones. Furthermore, five of the approved apps did not provide a calculable measure of their effectiveness at all. In one notable case, an app for smoking cessation failed to show a benefit when looking at all the users who started the program, only showing success when researchers looked at a smaller group of people who actually used it frequently. In another case, an app for speech disorders was approved based on a study that had no control group to compare against, making it impossible to know if the app caused the improvement or if patients would have improved on their own.
The researchers found that the type of treatment mattered greatly. Apps based on psychotherapy, which guide users through cognitive exercises and behavioral changes, made up the largest group and generally showed consistent, meaningful results. These were most effective for depression and anxiety. In contrast, apps designed to help with physical rehabilitation or complex behavioral changes like quitting alcohol showed more modest results. The study also highlighted that the size of the benefit often depended on how the app measured success. Apps that asked users to rate their own feelings on a questionnaire often showed larger improvements than those that measured hard physical data, such as blood sugar levels or walking distance, which are harder to change quickly.
Ultimately, the review suggests that while Germany's fast-track system has successfully brought a wide variety of digital tools to patients, the quality of the evidence supporting them is not uniform. For most of the forty-seven apps, doctors and patients can be confident that the tools work, backed by high-quality studies. Yet, for a small minority, the evidence remains opaque, relying on unreviewed data or missing key details about how much the apps actually help. The authors conclude that for the system to remain trustworthy, it is essential that all permanently approved apps publish complete, peer-reviewed results that clearly state the size of their benefits. Without this clarity, doctors cannot make fully informed choices about which digital tools to prescribe, and patients cannot know if the app they are using is truly the best option for their health.
Drowning in papers in your field?
Get daily digests of the most novel papers matching your research keywords — with technical summaries, in your language.