Introduction

The biopsychosocial model as characterized most notably by George Engel [1] is an essential asset for the field of Psychosomatic Medicine. But how to avoid vacuous and arbitrary “holistic” statements and how to validly apply this model to actual research and care of patients is a question not easily answered.

Diagnostic Criteria for Use in Psychosomatic Research

Few, if any, have dedicated as much conceptual inspiration and hard research and clinical work to answering it as Giovanni Fava and his group of talented researchers and clinicians. The journey was well under way already 30 years ago, when Giovanni published a mission statement on the concept of psychosomatic disorder [2]. It describes his intention of refining the methods for diagnosing psychosocial aspects of disease in medicine, motivated not least by his critical assessment of the then and now current “gold standard” of diagnosing mental symptoms and disorders with the Diagnostic and Statistical Manual of Mental Disorders (then DSM-IV, now DSM-5-TR) [3, 4]. The concept of “abnormal illness behavior” (AIB), i.e., the persistence of a maladaptive mode of perceiving, experiencing, evaluating, and responding to one’s health status, is a primary focus of his attention to relevant psychosocial aspects not covered in the DSM-III-R approach. The delineation of different modes of AIB he provides in 1992 is a precursor to the next important step in his journey when, in 1995, he published, with an international group of co-authors, the Diagnostic Criteria for Psychosomatic Research (DCPR) [5].

In its current revised form, the DCPR [6] comprises 14 psychosomatic syndromes with 3–4 precisely described criteria, each of which can be elicited in a semi-structured interview. Thereby, these criteria transform psychosocial factors into operational tools, allowing for their application in so-called clinimetrics in research and clinical care. The 40-year development and history of clinimetrics was recently succinctly summarized by G.A. Fava [7].

The clinimetric approach by Fava et al. [6] divided the syndromes into the following 4 groups.

Stress: allostatic overload.

Personality: type A behavior, alexithymia.

Illness behavior: hypochondriasis, disease phobia, thanatophobia, health anxiety, persistent somatization, conversion symptoms, anniversary reaction, illness denial.

Psychological manifestations: demoralization, irritable mood, somatic symptoms secondary to a psychiatric disorder.

Particularly the dimensions “demoralization and irritable mood,” both already introduced in 1995 [5], are still highly relevant to date, and a recent systematic review on allostatic load and its impact on health [8] has impressively summarized the special importance of this construct. To summarize, many single studies and several reviews [9] have shown that these criteria are very useful in differentiating subgroups of patients in a clinically meaningful way in multiple medical and psychiatric settings, regardless of the “functional” or “organic” nature of the illness. This proves that the DCPR criteria achieve, in contrast to other approaches claiming this label, a truly “personalized medicine.”

Irrespective of these successes, the journey of Fava and colleagues will certainly continue. One might expect, for instance, that the rationale for selecting, e.g., thanatophobia and anniversary reaction and for omitting potential other psychosocial factors like “distrust in the health care system” or “high utilization of the health care system” will be further elaborated on. This process might also be helped by referring the single psychosomatic syndromes to a framework that is even more overarching than AIB like, e.g., the enactive approach of viewing psychosomatic disorders as disorders of sense making or, in other words, as disorders of the embodied self [10, 11].

How can Fava et al.’s DCPR [5, 6] be positioned within the most relevant diagnostic classification systems? Fava and colleagues published the original DCPR three decades ago, shortly after the appearance of ICD-10 [12] and DSM-IV [3]. The closest relationship is found between the syndromes defined in the DCPR and functional disorders, somatoform disorders, and somatization disorders defined in ICD-10 and DSM-IV. Fortunately, in recent years, the scientific community has distanced itself from the stigmatizing diagnostic concepts described in ICD-10 and DSM-IV for somatoform and somatization disorders, describing patients as “difficult,” unable to accept that somatic symptoms are not caused by specific pathophysiological mechanisms, and therefore asking for repeated medical examinations. To Fava et al.’s credit, the DCPR never adopted this stigmatizing diagnostic view.

The American Psychiatric Association and the World Health Organization published their new diagnostic manuals in 2013 with a text revision in 2022 (DSM-5 and DSM-5-TR) [4, 13] and in 2019 (ICD-11) [14], respectively. The successor concepts for somatoform disorders, namely, somatic symptom disorder (DSM-5-TR) and bodily distress disorder (ICD-11), were considered imprecise by some researchers, including Fava and Cosci [15, 16] whose revised version of the DCPR [6] does not include a corresponding concept for either somatic symptom disorder or bodily distress disorder. Of note, the authors of the DCPR designed it as a complementary system to the ICD and DSM classification, not with the aim of replacing them. However, a current scoping review based on the published evidence since the appearance of DSM-5 concluded that with the application of the diagnostic criteria for somatic symptom disorder, a both somatically and psychologically substantially impaired patient population is described [17], which justifies giving a diagnosis and the initiation of therapy. In addition, the review revealed that the diagnosis of somatic symptom disorder has good reliability, validity, and clinical usefulness, clearly better than its predecessor diagnoses [17, 18].

Current Discussion of Diagnostic Criteria in the Field of Persistent Somatic Symptoms

While the original version of the DCPR included diagnostic criteria for “functional somatic symptoms secondary to a psychiatric disorder” [5], these criteria were revised to “somatic symptoms secondary to a psychiatric disorder” in the updated version of the DCPR [6]. However, psychological and somatic symptoms are usually deeply interwoven, and clear temporal or even causal interrelationships are in many cases difficult to determine. Clearly, the DCPR is also committed to the biopsychosocial model; thus, the designation “secondary to” should not be understood as causal. Just recently, the EURONET-SOMA group has proposed a new classification for functional somatic disorders [19], which might occupy a neutral space within disease classification systems, favoring neither somatic disease etiology nor mental disorder [19]. Also, of particular interest is the development of the Hierarchical Taxonomy of Psychopathology (HiToP), which aims to reflect psychopathological dimensions in an evidence-based hierarchical dimensional framework [20]. Thereby, a somatoform entity, located in the internalizing spectrum of the HiToP classification, seems to become increasingly empirically established [21, 22].

It must be the goal of a sophisticated diagnosis to describe the patient’s symptoms as accurately as possible, and this includes that the characteristics of the affected patient are described as comprehensively as possible. Thus, parallel to a diagnosis of somatic symptom disorder (DSM-5-TR) or bodily distress disorder (ICD-11), it should also at least be examined whether the diagnostic criteria of a functional somatic disorder (ICD-11/EURONET-SOMA) [19] are met. If so, the diagnoses of a functional disorder and a somatic symptom disorder/bodily distress disorder should be assigned comorbidity. In addition, the DCPR and the HiToP criteria should also be applied. In this way, they can be scientifically compared and validated with each other, and the affected patient can be best characterized until generally agreed and empirically based diagnostic criteria are available.

Recent scientific insights into the mechanisms underlying persistent somatic symptoms will also contribute to the diagnosis and treatment of a wide range of psychosomatic disorders in the future [23]. These include, for example, the recognition that symptom perception is a generative process that can best be explained with predictive coding models [24, 25]. Current empirically based models have already incorporated this knowledge and also clearly indicate that the etiology of persistent somatic symptoms is biopsychosocial and multifactorial [23, 26].

With the development of the DCPR and its scientific discussion, Giovanni Fava and colleagues have made significant contributions to the further development of the diagnosis of mental disorders, and with the DCPR, they have developed a clinically useful tool. It is hoped that in the long run, this work will contribute to our major common scientific goal of an empirically based and generally accepted diagnostic system of mental disorders.

Involvement of the Patient Perspective in Clinical Medicine

Alvan Feinstein, the pioneer of the clinimetric approach already described in his landmark paper, published in the Annals of Internal Medicine 40 years ago (1983), his approach as follows: “The domain of clinimetrics is concerned with quantitative methods in the collection and analysis of comparative clinical data, and particularly with improved ‘measurement’ of the distinctively clinical and personal phenomena of patient care” [27]. In an editorial, N. Sartorius [28] summarized the special value of patient-reported outcome measures (PROMs) as a relevant involvement of the patient perspective and stated that “The recent trend for recognizing the need that patients actively participate in the assessment of the outcome of treatment is a welcome development, not only because it adds valuable data, but also because its recognition of the partnership role that the patients should have in research on outcome of mental illness” (N. Sartorius). Although we value the PROMs as self-rated scales and indices developed to improve the detection of the patients’ subjective experience, we have to evaluate their validity and usefulness in a specific research or clinical setting. Carrozzino et al. (2021) [29] discussed the relevance of the clinimetric methodology in choosing the appropriate PROMs. They called their concept the “CLIPROM criteria” and stated that they may also guide the development of new indices and the validation of existing PROMs to be employed in clinical setting.

In somatic medicine, mandatory psychosocial stress screening is well established, particularly in the field of oncology. In Germany, in order to obtain the status of a comprehensive cancer center, it is mandatory that cancer patients undergo psychosocial stress screening. A number of short screening instruments have been established. In addition, innovative approaches using digital tools also directly record the patient’s further psychosocial care wishes and forward them electronically to the corresponding psycho-oncology unit at the end of the survey. This approach creates a direct link between diagnostics and treatment [30]. The large field of post-COVID-19 syndromes is another highly relevant area where a consistent expansion to a biopsychosocial perspective and framework is urgently needed in diagnostics and the derived therapeutic options [31]. In particular, the post-COVID fatigue is recognized as one of the most commonly presented long-term complaints in individuals previously infected with SARS-CoV-2 [32]. In this area in particular, subjective theories of illness and inferred illness behaviors will play a central role in illness coping and recovery.

Structured postgraduate programs at the national and European [33, 34] level are needed to develop the adequate research questions and the appropriate research design in our discipline. However, in order to successfully conduct translational and clinical research in the field of psychosomatic disorders, access to clinical treatment settings is also needed. Therefore, in the next paragraph, we will briefly report on the particular structure of psychosomatic medicine and psychotherapy in Germany as a timely model.

From Diagnostics to Therapy

To bridge the gap from diagnostics to therapy in the following paragraph, we provide a short update [35, 36] of the clinical infrastructure and specialization training for psychosomatic medicine in Germany, which is unique in international comparison. The “German way,” with its own specialist and corresponding psychosomatic facilities, is also one of the essential prerequisites for the development of our discipline in recent decades.

The institutionalization of psychosomatic facilities at German universities in 1970 and the introduction of the specialization of Psychotherapeutic Medicine in 1992 (the title was changed to Psychosomatic Medicine and Psychotherapy in 2003) set the stage for a rapid and continuous increase in the number of psychosomatic hospitals as well as psychosomatic practices in Germany. The residency in Psychosomatic Medicine and Psychotherapy requires a total of 5 years. Of these, 4 years must be completed in psychosomatic medicine and 1 year in another clinical specialty. At the core is a training in psychotherapy of 1,500 h under close supervision (every 4th hours of therapy), which can be done in three different tracks (psychodynamic track, cognitive-behavioral therapy track, or systemic/family therapy track).

Inpatient Treatment

The most recent publication of the Federal Office of Statistics’ (Destatitis) report of 278 psychosomatic hospitals with a total of 12,733 beds in 2020 and 156 day-patient units [37] (Destatis, April 2022). The mean duration of treatment across all hospitals was 40.8 days. Furthermore, 156 psychosomatic facilities provide treatment in day clinics. The growth of psychosomatic medicine and psychotherapy was associated with increasing differentiation into different structures and types of hospitals, ranging from smaller psychosomatic departments in university hospitals, general hospitals, and centers for psychosocial medicine to larger psychosomatic hospitals. The majority of psychosomatic hospitals are integrated into somatic and general hospitals. In sum, psychosomatic medicine shows – as a relatively young specialization – a development within the last 30 years that is unique compared to all other medical specializations in Germany.

Psychosomatic hospitals and day clinics offer well-established treatment programs which are centered on multimodal and integrated care for the following psychosomatic and mental disorders: somatic symptom disorders, eating disorders, dissociative disorders, somatopsychic disorders (e.g., psycho-oncology), psychotraumatology, depressive disorders, anxiety disorders, and personality disorders. Compared to outpatient treatment, multimodal inpatient treatment provides a “combination therapy” integrating classical psychotherapy with specialist therapies (e.g., body, art, music therapy), primary nursing, relaxation therapy, physical therapy, competence trainings, social counseling, and involvement of the family.

Multimodal inpatient treatment in psychosomatic hospitals has been shown to be effective in numerous studies. However, findings are restricted to naturalistic studies as the design of RCTs is impaired by methodological, pragmatic, and ethical reasons [38]. A prospective naturalistic study was initiated at 19 German university hospitals for psychosomatic medicine and psychotherapy, which included a total of 2,094 patients and is currently in final evaluation [39]. A previous systemic review and meta-analysis including 59 studies on inpatient treatment reported a medium within-group effect size for symptom change of d = 72. The lower effect size in the meta-analyses may result from a lack of standardized assessments and small sample sizes of the included studies [40].

Outpatient Treatment

The psychosomatic-psychotherapeutic treatment is offered mostly on an outpatient basis. Of a total of 4,126 practicing psychosomatic specialists in Germany [41], two-thirds work in outpatient settings predominantly in private practice, one quarter in hospitals, and the rest in other fields including public health departments.

The outpatient psychosomatic health care service consists of a tripartite system including general practitioners with a training in psychosomatic basic care (“Psychosomatische Grundversorgung”), specialists in somatic medicine with an additional qualification in psychotherapy, and specialists for psychosomatic medicine and psychotherapy. This allows a differentiated and need-based stepped care approach in psychosomatic health care in Germany. Specialists for psychosomatic medicine and psychotherapy together with other specialists with an additional qualification in psychotherapy overtake the major part of medical psychotherapy in Germany. Specialists in psychiatry and psychotherapy often show a different treatment focus and offer classical psychotherapy to a lesser extent.

Psychosomatic specialists work at the interface between clinical/somatic and mental disorders. Their therapy profile is broader than focusing exclusively on classical psychotherapy. Their work includes the evaluation of psychosomatic aspects in clinical diseases to work on a psychosomatic disease understanding, psycho-educative interventions, preventive interventions, and crisis interventions. However, these specialist interventions are not financed adequately by the insurance, making it less attractive to offer, e.g., an open psychosomatic consultation hour. In sum, Psychosomatic Medicine and Psychotherapy has also shown a dynamic development in the outpatient sector in the last 30 years. However, the general conditions of the outpatient specialization, financing, and need for ambulatory psychotherapy planning have to be adapted to further improve psychosomatic health care in Germany.

A Tribute from German Psychosomatic Medicine

As representatives from the German psychosomatic field, we not only want to thank Giovanni Fava for his incredible job as editor of our most influential journal, his impact on the field of clinimetrics, and not to forget his impact on the development of a tailored and very well-conventionalized Well-Being-Therapy but also for sharing his views and his clinical experience on a regular basis with the German psychosomatic field. In his editorials with the title “Fava’s Pen” in our central journal Ärztliche Psychotherapie und Psychosomatische Medizin, Giovanni Fava presents very interesting and critically reflective case histories of successful and enriching encounters from a physician’s and patient’s perspective – and he summarizes his abundant experiences under the motto: “the really important thing is that we both wanted to get out of the tunnel!” A summary of his contributions was published recently in a book with the very enigmatic title “Not Sick Is Not Healthy Enough” [42].

Acknowledgments

All authors are professors at German Departments of Psychosomatic Medicine and Psychotherapy. Parts of this editorial were presented by Stephan Zipfel at the 26th ICPM conference in Rochester, NY, USA, 2022.

Conflict of Interest Statement

The authors have no conflicts of interest to declare.

Funding Sources

No funding sources were involved in writing of this editorial contribution.

Author Contributions

All authors (Stephan Zipfel, Bernd Löwe, Katrin Giel, Hans-Christoph Friederich, and Peter Henningsen) had made substantial contributions to the conception of the editorial. Stephan Zipfel, Bernd Löwe, and Peter Henningsen were particularly involved in designing the part on “Diagnostic Criteria for Use in Psychosomatic Research,” whereas Hans-Christoph Friederich and Katrin Giel drafted the chapter “From Diagnostics to Therapy.” All authors were involved in reviewing and final approval of the version to be published.

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