Commentary: The framework for systematic reviews on psychological risk factors for persistent somatic symptoms and related syndromes and disorders (PSY-PSS)

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Introduction
A framework (1) for research on psychological risk factors for persistent somatic symptoms (PSS) is a milestone in stimulating and improving future research in this area, and we appreciate the attempt to systematize the complex field of PSS by defining relevant patient groups and psychological variables.In their work, the authors attempt to compile a comprehensive list of search terms for further systematic reviews on psychological risk factors for PSS and PSS-related outcomes (PSY-PSS).However, the paper omits factors related to personality functioning and mentalizing (2, 3) that are highly relevant for the understanding and treatment of patients with PSS (4)(5)(6)(7)(8).In this commentary, we therefore want to outline further areas of psychological risk factors that have already shown their significance for patients with somatic symptom disorder (SSD) and in other PSS-related syndromes and disorders, such as irritable bowel syndrome (IBS).

Risk factors in patients with PSS related to personality and personality functioning
First, we would like to acknowledge that a number of factors related to personality are already integrated in the list provided by the authors (1).Notably, the reception of alexithymia, emotion regulation, adverse childhood events, parent-child relationship, and interpersonal factors does also partly include a perspective of PSS as a disorder related to attachment and affective processing (9).The concept of alexithymia especially refers to an emotional blindness with specific deficits in distinguishing and expressing emotional states (10).Relatedly, the cognitive-developmental model of emotional awareness conceptualizes different states of emotional understanding (11) and has been evaluated in patients with somatoform disorders (12).Alexithymic characteristics in this patient group describe the difficulty of identifying and describing feelings that go along with the misinterpretation of bodily sensations that accompany emotional arousal (13).In addition to individual deficits, emotional avoidance often fulfills an interpersonal function in patients with PSS (14).However, modern approaches describe phenomena of alexithymia regarding affective processing as deficits in embodied mentalization (15), deficits in affective theory of mind ( 16), or as specific deficits of basic abilities such as affect differentiation or affect tolerance (3), all of which share an explicit or implicit dimensional model of personality functioning.Surprisingly, these aspects are missing in the presented framework (1).

Empiric evidence of deficits in mentalization and personality functioning
In the next section, we will briefly outline the importance of personality-oriented variables such as mentalizing or-more broadly speaking-personality functioning for understanding and treating patients with PSS.According to the concept of embodied mentalization, a main problem of patients with PSS is to distinguish emotional and physical states from each other and to classify them in a reflective way (15).Mentalization capacity is shaped by early mirroring and containing processes within the parentchild-relationship (2).A prospective study showed a significant negative relationship between maternal sensitivity at 18 months and somatization at age 5 years as well as a strong connection between attachment anxiety and health anxiety in adulthood (17).From this perspective, current psychodynamic therapies for patients with PSS have been derived, which aim at three key systems: attachment, mentalizing, and impairments in epistemic trust (18).This adds to other meta-analytic evidence for the effectiveness of psychodynamic approaches in functional somatic disorders (19).Furthermore, a recent systematic review stresses the need to integrate dimensional assessment of personality functioning in patients with SSD (20).The concept of structural integration or personality functioning has many similarities with the DSM-5 AMPD and ICD-11 approach for personality disorders (21).Empirically, personality functioning served as a mediator between childhood maltreatment and somatic symptoms and mental health due to capacities of self-reflection, regulation and identity formation (22).Finally, personality functioning can be directly used for tailored treatment planning (23, 24) and therefore should not be neglected in research about PSS.
More specifically, the importance of deficits in mentalizing and personality functioning, especially specific structural deficits in affective processing, are empirically well-supported for patients with PSS: In recent studies, patients with IBS showed higher mentalizing deficits than healthy controls (4, 8) and patients with inflammatory bowel diseases (4).Additionally, in gastroenterological patients, the diagnostic B-criterion of SSD was associated with higher mentalizing deficits and deficits in personality functioning according to the Operationalized Psychodynamic Diagnosis System (6).Furthermore, experimental research indicates that higher order emotional awareness, which includes comprehension as a form of mentalization compared to symptom attention without comprehension, protects from somatic complaints (7).A further study compared patients with IBS and healthy controls according to specific dimensions of affective processing and showed that the deficits are especially prominent in understanding and tolerating difficult affective states captured as affect tolerance and affect differentiation (5).Both are subscales of the OPD-SQ (25), which is recommended as a measurement tool in a narrative systematic review on emotion regulation processes in SSD and related conditions (26).From these results, it was hypothesized that deficits in understanding and regulating physical and emotional states-as it is part of the mentalization and personality functioning concept-are functionally connected to increased anxiety, worry, and behavioral preoccupations in patients with SSD (6).

Discussion
In this General Commentary we report the empiric evidence of deficits in mentalization and specific structural deficits in affective processing in patients with PSS and related syndromes as IBS.So far, mentalization, reflective functioning, embodied mentalization, affective theory of mind, psychic structure, personality functioning, affect tolerance and affect differentiation are not integrated as search terms in the referred systematic review (1).Empirical evidence tentatively suggests their relevance for patients with PSS, including related empirically supported treatment models, which would otherwise be excluded, and therefore we argue for their inclusion.Overall, we appreciate the effort put forth by Hüsing et al. and believe that by including these additional psychological risk factors, their framework could serve as an even more valuable resource for researchers, clinicians, and other stakeholders in the field of PSS.