Exploring the comorbidity of musculoskeletal and personality disorders among adults: a scoping review protocol

Separately, mental and musculoskeletal disorders (MSDs) are prevalent across the life course and are the leading contributors to disability worldwide [1, 2]. In 2010, mental disorders [1, 3] were the leading cause of years lived with disability (YLDs), with MSDs being the second [4]. By 2017, major depressive disorder (MDD) was identified as the main driver for mental disorder-related disability, with low back pain the leading cause of the musculoskeletal-related disability, but the order of these two main disease classes remained the same in respect to YLDs [2]. Combined, mental disorders and MSDs are now estimated to account for over 30% of the global YLDs [5, 6]. Little improvement in population health is reported in relation to these disorders—and the associated burden is expected to rise, given increasing population growth and ageing [1, 2].

Recently, a review of the literature reported associations between mental disorders and MSDs among middle-aged and older adults showing that those with depressive and anxiety disorders and poor subjective mental health had compromised bone health and increased risk of osteoporotic fractures, respectively [5]. Furthermore, certain medications used in the treatment of mental disorders have also been shown to independently affect bone [7]. Elsewhere, there is a suggestion that the risk of falling, and associated fracture, may be exacerbated by the presence of depression [7, 8] and other types of mental ill health [9, 10]. However, personality disorder (PD), an often-severe form of mental ill health, with far-reaching public health implications including comorbidity with other physical health conditions [11], has not been thoroughly explored in relation to MSDs. This is despite burgeoning research showing PD co-occurs with sleep disorders, headache and pain disorders, obesity, and other chronic health conditions [11]. People with PD symptomology also perceive their overall health to be worse than people without [12] and report difficulties with general health care compliance [13]. Separately, PD is also associated with high direct medical costs, and high costs, due to productivity loss [14]. However, little is known regarding the burden associated with PD and MSD comorbidity specifically.

By definition, PD is marked by patterns of distressing behaviours, ways of thinking, emotionality, and inner experiences that differ significantly from those in one’s usual social/cultural context—causing significant impairment in important areas of life and distress [15]. PD usually emerges earlier in the lifespan and can be relatively more enduring, inflexible, and disabling than other forms of mental ill health [15]. Traditionally, specific PDs include paranoid, schizoid, schizotypal, antisocial, borderline, histrionic, narcissistic, avoidant, dependent, and obsessive–compulsive PDs [15]. However, there is variation between the two main classification systems (i.e. International Classification of Diseases [ICD] and Diagnostic and Statistical Manual of Mental Disorders [DSM]), in terms of definitions and approaches to diagnosis—with longstanding and unresolved commentary in the literature concerning these issues [16, 17]. Still, their clinical significance is not contested, and exploring their relationship to MSDs and the burden associated with their comorbidity is warranted, given the known links between PD and other adverse physical health outcomes.

A preliminary search revealed no prior review on the proposed topic. One systematic review, however, was found, which reported that people with serious mental illness including schizophrenia, bipolar disorders, depression, and depression with borderline PD had lowered bone mineral density [18]. However, the authors chiefly examined osteoporosis or fractures as outcomes of interests, and other types of burdensome MSDs were not explored. Also, given that PD was not examined as a risk factor per se, studies with a focus on PD in relation to MSDs may have gone undetected. The proposed scoping review will be a valuable contribution to the literature, as it will broaden the currently narrow research focus on common mental disorders and physical comorbidities—and stimulate further research on this topic.

Therefore, we propose to undertake a scoping review to explore the existing clinical- and population-based literature, the comorbidity of PD and MSDs among adults ≥ 18 years, and the potential burden associated with their comorbidity; identify knowledge gaps on this topic; and propose recommendations for future research.

This protocol is guided by Arksey and O’Malley’s five-stage methodological framework [19]—and the extensions to this original framework developed by the Joanna Briggs Institute (JBI) [20, 21]. This protocol is registered in Open Science Framework Registries (https://​osf.​io/​mxbr2/​) and complies, where relevant, to the Preferred reporting items for systematic review and meta-analysis protocols (PRISMA-P) 2015 checklist (see Additional file).

This protocol is structured as follows [19]:

The final scoping review will adhere to and present the PRISMA extension for Scoping Reviews checklist as supplementary material [22]. Each stage is described in more detail in the following sections.

The proposed scoping review will extend existing reviews by employing a robust search strategy to explore, uncover, and bring together in one review what is known regarding the comorbidity of PD and MSDs from published and unpublished evidence sources in both population-based and clinical settings. Uncovering and synthesising the available evidence on this topic may prompt future research including systematic reviews and meta-analyses. It may also reveal literature that describes or postulates the underlying connection between PD and MSDs, and/or the burden associated with their comorbidity. These insights may lead to an improved understanding of the experiences of people with these comorbidities and treatment targets.

In terms of dissemination, the ensuing scoping review will be submitted for publication in a scientific, peer-reviewed journal. The findings from the proposed scoping review may be presented at relevant conferences and used to inform the development of future research studies.

In terms of potential limitations, the nature of the scoping review is exploratory, and the reviewed studies will likely vary widely in terms of their methodology—including definitions of PD, all of which preclude a systematic review or meta-analyses [21, 34]. To overcome these restraints, a scoping review methodology will be the most appropriate methodology to address the research objectives, given the knowledge base on this topic is still emerging and not well understood. Consistent with published guidance [35], critical appraisal will not be performed on eligible studies. However, a summary of the strengths and limitations of reviewed studies will be reported in the discussion. Ethics approval is not required for this scoping review.

The proposed scoping review will valuably contribute to the literature as it will be the first review to explore and provide a descriptive synthesis of what is known regarding the comorbidity of PD and MSDs among adults in different contexts—while offering future research directions.