Introduction

The current version of the Diagnostic and Statistical Manual of Mental Disorders (DSM-5) defines SSRDs as a set of psychopathological manifestations characterized by physical symptoms not attributable to organic pathology. The common feature of these disorders is the symptoms prominence neither intentionally produced nor simulated; some medical conditions may be present; however, this can explain neither the intensity nor the pathophysiological mechanisms [1].

These diseases incidence is growing sharply, especially in childhood and adolescence, with a higher prevalence in the female population.

SSRDs include somatic symptom disorder (SSD), conversion (functional neurological symptom disorder), illness anxiety, factitious disorder, psychological factors affecting other medical conditions, additional specified somatic symptoms and related illnesses, unspecified somatic symptoms, and related disorder.

The research examined only the disorders where physiotherapy treatment is reported and indicated as somatic symptoms, conversion disorder, and fictitious disturbances.

Somatic Symptom Disorder is defined based on three criteria and three specifiers described in Table 1. Diagnostic criteria for conversion and fictitious disorders are shown in Tables 2 and 3.

Table 1 The diagnostic criteria for Somatic Symptom Disorder noted in DSM 5
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Table 2 The diagnostic criteria for Conversion Disorder noted in DSM 5
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Table 3 The diagnostic criteria for Factitious Disorder noted in DSM 5
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Currently, there is a lack of precise data referring to the European situation, but according to a recent American study, these disorders cost the US health system up to 100 billion dollars a year [2, 3].

The role of poor physical activity as a risk factor in developing SSRDs is well known. A study [4] revealed a strong correlation between a low level of physical activity (b = 0.005, bootstrap 95%-IC: 0.01 to 0.09) in a cohort of 1816 adolescents with SSD, a sedentary life (b = 0.10, bootstrap 95%-CI: 00.6 to 0.14) and the onset of the disorder. Furthermore, in a consolidated pragmatic perspective, physicians are aware of the protective role of physical activity in preventing SSD. Besides, regular physical exercise can also facilitate social relationships, avoiding isolation, an additional well-known risk factor [5]. A recent study reported that 10% of patients with mental health problems entered the hospital using walking devices such as wheelchairs or crutches not required by any clinical diagnosis [6]: these patients had a greater need for multidisciplinary support with paediatricians, child psychiatrists, psychologists, nurses and physiotherapists [7].

The physiotherapist is considered an essential role within the multidisciplinary team for these reasons. However, the proposed interventions are very heterogeneous, and the evidence of their efficacy is limited [8].

This systematic review aims to evaluate the available evidence on the effectiveness of physiotherapy treatments in the paediatric population affected by SSRDs.

Materials and methods

Search strategies

For this review, we conducted a literature search on the following electronic databases: MEDLINE / PubMed, CINAHL, Cochrane Library, PsycINFO, and PEDro, using the terms listed in Table 4, split according to the population, pathology, and treatment groups.

Table 4 Keywords used for database searches
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Inclusion and exclusion criteria

The inclusion and exclusion criteria employed to select the articles are described in Table 5.

Table 5 Inclusion and exclusion criteria
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Due to limited publications and poor methodological quality, we considered all research in electronic databases from 1999 to October 2021. Regardless of the study design, we selected all the papers written in Italian and English in full-text form.

Studies with a population of patients aged 8 to 21 years with SSRD disorders (defined according to DSM-5 criteria) requiring physiotherapy treatment, i.e., somatic symptom disorder, conversion disorder, and factitious disorder, were included. Research that considered illness anxiety disorders, disorders with psychological factors affecting other medical conditions, and publications dealing with the definition of “general chronic pain” in children were excluded.

Only the publications in which physiotherapy treatment was cited and described, albeit briefly, in its objectives and methods were examined, while research that did not indicate efficacy results was ruled out.

Selection of studies

By searching the databases with the keywords mentioned above, 987 studies were selected, with seven additional publications taken from the reference bibliographies of some chosen articles (Fig. 1). Thirty-six full-text articles were evaluated for eligibility, and only 9 met the inclusion criteria. Twelve publications were rejected as they did not describe the objectives and methods pursued by the rehabilitation treatment. We excluded four works that did not consider the effectiveness of the treatments described, and six studies were dropped due to patients with symptomatic manifestations that did not meet the diagnostic criteria of the DSM-5. Finally, four articles were ruled out because they included subjects over 21 in the study population.

Fig. 1
figure 1

Study selection flow chart

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The articles were searched between July and September 2021 and involved two independent reviewers, R.S. and A.D.T., who simultaneously selected the papers starting from title and abstract following the inclusion and exclusion criteria. A third reviewer, R.C., resolved any disagreements.

Characteristics of the studies

The characteristics of the studies examined are described in Table 6. The age of the participants varied from 0 to 21 years. In five studies [9,10,11,12,13], treatments were proposed during hospitalization, while only one was chosen as an outpatient setting [14]. An initial course of treatment was performed in the hospital in the remaining three, followed by outpatient treatment [8, 15, 16]. Treatments and hospitalizations' duration was very variable, [8, 9, 11] ranging from 3 to 78 days of hospitalization, [9] with a duration of treatment from three days to two years [8]. Furthermore, it was not reported, except by an author, [16] whether the treatment started in hospitalization continued after discharge, following specific modalities, intensity, and setting [9,10,11,12, 17]. Few papers indicated the intensity of the treatments, regarding the duration of the single session [12] and the frequency of treatments. Follow-up times varied considerably from two months [12, 16] to one year [12], and in three studies, the duration was not indicated [11, 14, 17]. Five of the investigations analyzed were case reports and retrospective case series [10,11,12, 14, 16], three were observational studies, [9, 15, 17] one was a systematic review [8], Most of the reviewed publications assessed a paediatric population with conversion disorder [8, 11, 12, 14, 17], two included somatic symptom disorder [10, 15], one examined SSRDs [16], and finally, in one article, the diagnosis was nonspecific and defined as pain associated with disability in paediatric age [9]. All the selected articles concluded that rehabilitation interventions were adequate for the outcomes considered.

Table 6 Characteristics of included studies
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Results

Table 7 shows the figures who are part of the multidisciplinary team to manage the patient with SSRDs. Except for two studies [14, 17], physiotherapy was described as part of a rehabilitation intervention in which various professional figures participated. Physiotherapists, psychologists, and doctors were always involved in the treatment process [9, 10, 12, 14, 15, 17].

Table 7 Members of the multidisciplinary team
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Table 8 shows the outcomes considered by the authors. The restoration of motor functions was the most used [9, 10, 14, 16, 17]; however, only in three studies, it was described with standardized measurement scales such as the Functional Independence Measure (WeeFIM) for children [9], the Functional Disability Inventory (FDI) [10], and the Functional Mobility Scale (FMS) [14]. In the remaining investigations, there was a generic descriptor referring only to the activities proposed in the rehabilitation program [15,16,17] or within overall assessments of the walk and daily life activities [11, 17]. Only one research [15] evaluated the level of activity and participation as result indicators, according to the International Classification of Functioning, Disability and Health for Children and Youth (ICF-CY). However, the adopted measurement scales were not reported, and the evaluative aspects of the field of body structure analysis were neglected. Two studies measured the quality of life, but only one [10] described the specific questionnaire utilized (Child Health Questionnaire—Parent Form 50). Although the improvement of muscle strength was assumed as a specific short-term goal in three publications, the adopted measurement scale did not appear. [10,11,12] In another study, improving postural control and balance was proposed as an integral part of the program; nevertheless, the chosen evaluation scales were not included [12].

Table 8 Considered outcome
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The days of hospitalization, reported by a few authors [9,10,11], had a wide variability ranging from three to 78 days [9]. In no study, the effectiveness of physiotherapy intervention was evaluated independently from the other rehabilitation proposals by the interdisciplinary team members.

Physiotherapeutic strategies were multiple, but only some studies reported the approach in detail [17](Table 9). Most authors [10, 14,15,16,17] proposed gradual exercises of increasing intensity and difficulty, structured so that performance could be rigorously measured. In all the investigations [9,10,11, 14,15,16,17,18], the importance of establishing clear short-term therapeutic goals (daily/weekly) was emphasized to provide rewarding result feedback to the patients. Empowerment and the therapeutic relationship were considered fundamental ingredients of treatment [8, 10, 14, 16, 17]. In most publications, the general objectives were stated with sufficient clarity. However, only in one study, the operational tools to achieve them were described to be reproduced [17]. In no study was the rationale behind the choices of personalized programs explicit.

Table 9 Proposed rehabilitation activities
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Evaluation of the methodological quality of research

The study design quality was assessed according to the guidelines indicated on the Equator Network for each type of research considered. Specifically, the following scales were used: STROBE (Strengthening the Reporting of Observational Studies in Epidemiology) for observational studies; PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) for revisions; CARE (CAse REports Guidelines) for case reports. The results are shown in Table 10.

Table 10 Methodological quality of the studies
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All the guidelines checklists used to assess the quality of the studies were divided into the sections such as title and abstract, introduction, methods, results, discussion of the results, and conclusions. The main problems were encountered in the paragraphs dedicated to illustrating the methods and the data processing. Apart from three publications [10, 11, 16] that met all the evaluation criteria, the remaining six were methodologically deficient, especially regarding the description of the study design, the statements of the methodological changes in progress, and the research strategies extraction and processing of the collected data.

No article described the result indicators chosen, nor did it report the evaluation scales used.

The CERT (Consensus on Exercise Reporting Template) guideline, a checklist comprising 16 items, was employed to estimate the quality of physiotherapy treatment reporting. The analysis of the articles demonstrated the poor quality of the description of the treatment programs adopted. No author described the devices (e.g., treadmill, exercise bike), the motivational strategies adopted, the progression of the exercises and their characteristics (repetitions, description of the modalities), or the proposed play activities. The only satisfactory items concerned the setting and description of qualifications, teaching skills, and training carried out by the exercise instructor. Our systematic review considered [8], while stating the lack of clear and precise descriptions of physiotherapy programs in most of the researchers analyzed, did not indicate the evaluation tool used to evaluate the reporting.

Discussion

This review could not confirm the effectiveness of physiotherapy in the setting of SSD in children and adolescents. Except for two [14, 17], all the reviewed papers considered physiotherapy in the context of the rehabilitation intervention for patients with SSD, which involved various professional figures. Therefore, it was not easy to establish whether and in what terms physiotherapy programs contributed to obtaining the declared results. Furthermore, the study designs, case reports, and observational studies were not appropriate for evaluating the effectiveness of the treatments, rendering the results unreliable. The previous systematic review [8] evaluated only the publications concerning the conversion disorder, concluding that there was no clear evidence of the effectiveness of physiotherapy at the current state of knowledge.

The physiotherapy treatments proposed by the various authors were very heterogeneous and neither reproducible nor comparable due to the lack of reporting quality and declaration of the measurement scales adopted [10, 11, 15, 16]. In addition, in various studies, they were classified as such techniques not specifically within the remit of the physiotherapist. The inclusion of these techniques, such as relaxation strategies [8, 9, 11], cooping [8,9,10], and the therapeutic relationship [8, 10, 14, 17], resulted in a less rigorous analysis of the results. The importance of attributing the achievement of specific goals to the competent specialist (for example, paediatrician, physiotherapist, occupational therapist, psychologist) was only emphasized in one research [16].

The choice of a rating scale capable of describing all aspects of the clinical manifestations of SSRDs was a critical factor. The ICF-CY was a standardized assessment tool capable of simultaneously contemplating both aspects of body structures and social behaviour. The ICF-CY organized information in two parts: the first dealt with functioning and disability, the second concerning contextual factors, allowing the evaluation of the functioning of the child and adolescent both from an individual and a social perspective. All authors agreed that it was essential to identify long-term goals, choose the correct level of difficulty for the exercises, and establish a solid therapeutic relationship, to achieve adherence to treatment and patient empowerment. No study cited short-term goals; only two detailed the physiotherapy intervention [16, 17], and only one described the device used [17].

In some studies, reference was made to a physiotherapy intervention model called "Restrained rehabilitation" [8, 10, 11, 16] based on a hierarchical scheme of the proposed activities and on the constraint of achieving the objectives shared with the patient for the discharge from the hospital. This approach was inspired by the therapeutic guidelines adopted for chronic fatigue syndrome patients at King's College Hospital [16]. The patient's favourite and most enjoyable activities became a motivating tool, a sort of reward and compensation [8, 16]. The maintenance of results over time was critical in evaluating the effectiveness of the treatment of SSRDs, since it could also relapse months later. Nevertheless, only three authors analyzed a follow-up time of more than three months [9, 10, 15], while others did not consider it [11, 14, 17].

The intensity of the physiotherapy treatment was a critical element impacting its effectiveness. Nevertheless, only one author [16] reported the frequency and duration of the interventions in hospital and outpatient settings. In the remaining articles, it was unclear whether and how the physiotherapy approach adopted during hospitalization was subsequently proposed after discharge [9,10,11,12, 17].

By analyzing the length of hospitalization, we noticed a wide variety, ranging from 3 to 78 days. Gooch's study claimed that this difference was based on the heterogeneity of cases detected within a population with the same diagnosis, the conversion disorder, and treated with the same type of rehabilitation intervention. The wide variety and severity of symptomatic manifestations in SSRDs explained, on the one hand, the difficulty in conducting methodologically rigorous randomized controlled trials and, on the other hand, the absence of physiotherapy treatment protocols adaptable to different clinical scenarios.

The most critical aspect in reviewing publications on SSRDs was the rigorous selection of research based on the explicit criteria for the diagnostic definition of SSRDs and the failure to use standardized efficacy measures in research. The SSRDs constituted a new nosological category, inserted in the latest version of the DSM-5, which replaced the previous one of the DSM-IV, in which, for example, the DSS were classified as "somatoform disorders". Therefore, the disorders were categorized according to the previous nosological classifications in many articles, which modified the diagnostic criteria.

Despite the stated limitations, this review highlighted that we need to adopt a more rigorous methodological approach, paying particular attention to the quality of treatment reporting, to evaluate the efficacy of physiotherapy in treating SSRDs. If the proposals were not reproducible due to a lack of data relating to the choice of exercises, their duration, the frequency of the intervention, its possible changes in progress, and if standardized measurement scales were not used, it was practically impossible to compare the results and draw evidence-based conclusions. In the current state of knowledge, it was impossible to establish the effectiveness of the interventions performed and whether and in which clinical contexts one intervention was superior to another. It was essential to define possible physiotherapy protocols whose efficacy could be confirmed later by multicentre randomized controlled studies. SSD is a disorder showing a significant increasing trend, requiring multidisciplinary, time-consuming, costly and demanding treatment in the most severe cases. Although physiotherapy can play an essential role in this context, there is an urgent need to develop rigorous criteria defining the type of interventions and outcomes to establish their actual impact.

Conclusions

It was not possible to answer the review question regarding the efficacy of physiotherapy interventions in SSRD due to the low number of publications and their lack of methodological quality. Further randomized controlled pilot trials are needed, conducted with a rigorous research methodology, which pays particular attention to the reporting aspect and the evaluation of the effects of physiotherapy treatments independently from those obtained from the other proposals of the multidisciplinary team. Future research should also consider using the ICF-CY as a standardized assessment tool capable of describing outcomes related to the functioning of body structures and the levels of activity and participation of the child and adolescent from both an individual social perspective.