CHRONIC FATIGUE SYNDROME IN CANADIAN ADULTS: PROFILING DEMOGRAPHIC AND SOCIOECONOMIC FACTORS, MENTAL HEALTH DIAGNOSES AND CONDITIONS, AND LIFE EXPERIENCES

Background: Chronic fatigue syndrome (CFS) is a debilitating condition characterized by a complex assortment of biological, psychological, and functional issues. In the literature, while a debate persists in terms of CFS etiology and treatment options, very rudimentary queries also linger in terms of associated CFS demographic and socioeconomic characteristics, comorbid psychiatric diagnoses, and potentially deleterious life challenges and experiences which, if more definitively clarified, may help elucidate illness origin and management. Methods: Using data extracted from the Canadian Community Health Survey – Mental Health (CCHS-MH) (Statistics Canada, 2013) for adults aged 20 to 64 years of age, the current study developed a descriptive statistical profile of demographic, socioeconomic, psychiatric, and life experience characteristics of Canadians reporting a diagnosis of CFS. Further, a series of two-factor Chi Square tests were carried out to determine whether featured variables were significantly more likely for CFS sufferers as compared to adult Canadians without a CFS diagnosis. Results: It was observed that those reporting a CFS diagnosis were significantly more likely to be female, between the ages of 45-64, divorced or separated, living alone, unemployed or unable to work, and of relatively low personal income. CFS sufferers were also more likely to have comorbid psychiatric diagnoses including lifetime and 12-month Major Depressive Disorder (MDD), Generalized Anxiety Disorder (GAD), and substance dependence, as well as self-reported posttraumatic stress disorder (PTSD), attention deficit hyperactivity disorder (ADHD), sleeping troubles, and reported histories of childhood physical and sexual maltreatment. Conclusions: A very compelling demographic, socioeconomic, psychiatric, and life history profile of CFS sufferers emerged in this study, corroborating many findings in the literature.


Introduction
The disease state known as chronic fatigue syndrome (CFS) has gone by many names, including myalgic encephalomyelitis, systemic exertion intolerance disease, Gulf War syndrome, historically as neurasthenia/nervous exhaustion, or simply medically unexplained symptoms [1][2][3][4][5][6]. Along with the changes in nomenclature, have come many iterations of diagnostic criteria (See Table 1 for selected criteria). As the name suggests, CFS results in significant mental and physical exhaustion on the part of the individual [7], specifically resulting in a 50 percent reduction in activity level [3]. However, sufferers may also experience a range of immune and gastrointestinal symptoms, energy production and transportation impairment, and neurological symptoms including pain, cognitive decline, sleep disturbances, and sensory concerns [3] which can last for decades [8], resulting in a significant disease burden for this population.
As the diagnostic criteria have varied over the years, it has been difficult to fully establish demographic and socioeconomic characteristics of individuals with CFS, with heterogeneous findings across the current body of literature. This is also evident in the variability of prevalence rates, ranging between 0.2 to 3.2 percent depending on the criteria used, and whether based on clinician-assessment or self-report [9,10]. Nonetheless, women have been found to be 1. 5-2.7 times more likely to experience CFS [11,12], and depending on symptom severity, and given CFS's pervasive nature, many are unable to maintain employment, may require reduced work hours, or are completely housebound [11,13].
The limitations of employment and activity level have frequently been found to limit personal income capacity such that CFS is more often found within lower class households with an income discrepancy of $20,000 per year, or with total household incomes less than $40,000 per year [10,12,14,15,16]. Year Criteria Holmes et al. [54] 1988 Must have new onset of persistent or relapsing fatigue with no previous history of similar symptoms that does not resolve with rest, and impairs functioning below 50%, which is not better accounted for by another condition. An additional 8 of following must be present: mild fever, sore throat, painful lymph nodes, unexplained muscle weakness, muscle discomfort/myalgia, prolonged fatigue post-exercise, headaches, arthralgia without swelling or redness, neuropsychologic complaints, sleep disturbance, development over a few hours to a few days. Further, two of the following must also be documented by a physician: fever, pharyngitis, tender lymph nodes.
Fukuda et al. [55] 1994 Chronic (persistent or relapsing) fatigue for a minimum of six months, as well as four of the following: impaired memory/concentration, sore throat, tender lymph nodes, muscle pain, multi-joint pain, new headaches, unrefreshing sleep, postexertion malaise Carruthers et al. [56] 2003 New onset, unexplained, persistent, or recurrent fatigue, postexertional malaise, sleep dysfunction, and pain. Additionally, at least two cognitive symptoms, and at least one symptom from two of the following categories: autonomic, neuroendocrine, immune manifestations.
Carruthers et al. [3] 2011 Post-exertional exhaustion which lasts for a minimum of 24 hours, at least one neurological impairment (cognitive, pain, sleep disturbance, sensory/perceptual/motor), at least one immune/gastrointestinal/genitourinary impairment, at least one energy production/transportation impairment.
Note. Represents most commonly used definitions. Those which have not been used in the review of relevant literature have not been featured.
While it is unclear as to whether income limitations of individuals with CFS are a direct function of academic attainment levels, some evidence does suggest that the highest prevalence of CFS is among well-educated, white women [15]. However, this contention seems less reliable within the larger body of literature [17]. Regardless, the socioeconomic and employment challenges that seem highly associated with CFS often result in increased stigma which serves to exacerbate the severity of illness for sufferers [10,12,14,15,16,17]. This stigma is also perpetuated by the confusion surrounding the etiology of illness for this population.
While a number of possible causes have been explored, none have been able to independently account for the onset or maintenance of CFS. As such, it has been proposed that CFS be considered a set of symptoms rather than the result of one particular disease state [18].
Further, there is ongoing debate as to whether CFS might be best classified within the category in the DSM-5 of Somatic Symptom and Related Disorder (SSRD) [19]. This illness conceptualization captures the perspective that many healthcare professionals view CFS as a new label for medically unexplained somatic symptoms, whereby patients often continue to search for a medical cause in spite of continual negative findings [20]. However, this does not account for the numerous findings related to a biological origin of CFS.
With regard to a probable biological etiology, while 72 percent of individuals diagnosed with CFS believed their illness was related to a viral infection, only 33 percent were able to specifically verify such a history [7]. Viruses implicated in onset include enterovirus, Epstein-Barr virus, influenza, Hepatitis A, and toxoplasmosis, but such physical causes alone are insufficient to completely account for CFS onset and maintenance [21]. CFS sufferers have also been found to be immuno-compromised, have increased cellular stress linked to aging, as well as gastro-intestinal difficulties prior to the onset of illness [22]. Interestingly, in an effort to find a biomarker of CFS, an analysis of the electrical conduction of blood cells revealed that those with CFS had a significantly different electrical resistance pattern from a control group which may be unique to CFS [23]. While there have been findings of biological basis and physiological markers of illness, it is of particular interest that individuals who believe their CFS has a biological origin experience significantly more functional impairment than those who report other causes, such as psychological or social [8,13,24].
There has also been a focus on potential psychological influences with respect to the onset of CFS. Comorbidity of CFS with major depressive disorder (MDD), for instance, has led to suggestions that the manifestation of CFS is the experience of a psychiatric disorder primarily characterized by fatigue [2,25]. This interpretation stems from the overlap in physical symptoms seen in CFS and depressive mood disorders including fatigue, loss of energy, difficulty sleeping, and difficulty concentrating [19] but is perpetuated by several findings. Individuals with CFS, for example, have been found to present with significantly more symptoms of depression, and with greater symptom severity than individuals who are otherwise healthy, and those with autoimmune disorders [26]. Further, upon treatment, the remission of CFS symptoms often occurs in conjunction with remission of depressive symptoms, and the return of symptom severity of CFS occurs when depressive symptoms return [2].
Individuals with CFS also report significantly more traumatic life events, and greater perceived stress than non-CFS controls in the year leading up to onset and diagnosis [27,28].
Sufferers are also more likely to report clinically significant symptoms of PTSD than non-CFS controls [27]. Also of particular interest is the prevalence of early childhood trauma in this population. Not only have those with CFS been found to be significantly more likely than the general public to report emotional, physical, and/or sexual trauma during childhood, but the presence of childhood trauma has repeatedly been observed to predict fatigue, fatigue severity, and overall symptom severity in this population [27,28,30,31].
In addition to depressive and trauma-related disorders, several other psychiatric comorbidities have been implicated in the development and maintenance of CFS. Anxiety disorders, including social anxiety disorder and panic disorder have been observed to be significantly more prevalent among those with CFS than healthy controls, as well as individuals with other chronic health conditions [32,33]. Attention-deficit/hyperactivity disorder (ADHD) has also been found to be significantly more prevalent among CFS sufferers, as well as substance-related disorders, and sleep-wake disorders [33,34]. Further, a linear relationship between somatic and psychological symptoms has been demonstrated in individuals with CFS suggesting greater distress could result in increased severity of disease [25]. This finding would be consistent with the view of CFS as being possibly a SSRD whereby psychological distress presents in individuals as physiological symptoms [4]. However, not all individuals with CFS have a comorbid psychiatric disorder, and as such, this illness conceptualization has been insufficient in accounting for the prevalence of CFS [2,25].

Objectives and Rationale
To the best of our knowledge, there has never been a nation-wide assessment in Canada or the U.S. of the prevalence, demographic, socioeconomic, mental health, and life experience characteristics of individuals reporting a diagnosis of CFS. It would appear that previous research has consisted of small samples, with the largest state-wide cohort study conducted in Georgia in the U.S. [16], and one meta-analysis examining prevalence related to differing diagnostic criteria [9].
Additionally, research findings have been variable in terms of factors such as sociodemographic characteristics representative of CFS individuals. Some studies, for instance, have indicated that those diagnosed CFS are more likely to be white, middle-upper class women, while others report that CFS is observed equally across race, with significant variability in findings for gender and socioeconomic status [11,15,12,16,17,21].
Potential disagreement among researchers might be indicative of an underdeveloped appreciation of CFS, and specific characteristics those diagnosed with the disorder. Hence, in an effort to understand, diagnose, and better manage/treat CFS, this present study was designed to gain a better understanding of the population diagnosed with this disorder. Additionally, given the purported psychological involvement in the onset and maintenance of CFS, psychological comorbidities and influential life experiences are also explored. section below for details). While self-reported, previous research suggests that it is very unlikely for individuals with CFS to self-diagnose, implicating the indicator's reliability [12].

Data Collection
Data were collected via the CCHS-MH questionnaire, using computer assisted interviewing to ensure participants were asked only those questions which would pertain to them based on previous answers [35]. Participants were selected using random-digit dialing across Canada using pre-selected regions. The majority of interviews were completed in person, with the remainder conducted by telephone. and above), and employment status (i.e., whether respondent did not have a job, or was permanently unable to work). In terms of childhood trauma, the CCHS-MH employed the Childhood experiences (CEX) questionnaire, a six question self-report scale used to measure the instances of physical and sexual violence before age 16 [38]. For the purposes of the present study, two binary variables were created. Specifically, respondents were classified as experiencing physical maltreatment if they reported at least one incident of being "slapped, hit or spanked", "pushed, grabbed, shoved or thrown", or "physically attacked (i.e., kicked/ bitten/ punched/ choked/ burned/ other)" by an adult. Similarly, respondents were classified as experiencing sexual maltreatment if they reported at least one incident of "forced or attempted forced sexual activity."

Assessment of psychiatric disorders-
Data were analyzed using SPSS version 25. Descriptive statistics (i.e., percentages and frequencies) were compared between individuals reporting CFS, and the remaining CCHS-MH adult sample without a CFS diagnosis in terms of demographic, socioeconomic, psychiatric disorder, and other reported conditions. A series of two-factor chi-square tests were conducted to determine whether the likelihood of particular variables was depended on a CFS diagnosis.

Demographic and Socioeconomic Comparisons
Of the 16,972 adult respondents in the entire CCHS-MH sample, 277 reported a diagnosis of CFS by a health professional, or 1.63 percent. As presented in   Table 3 presents the proportion and frequency with which individuals with and without a CFS diagnosis meet the CIDI criteria for lifetime and current (12-month) psychiatric diagnoses. percent), χ² = 5.6, p < .018, cannabis dependence did not differ between the groups (See Table   3).

Other Reported Conditions
As shown in Table 3, CFS Respondents were significantly more likely to report a diagnosis of ADHD (9.

Discussion
The objectives of the present study were to establish a demographic, socioeconomic, psychiatric, and salient experiential profile of adult Canadians with CFS, and explore how they compare to adult Canadians not reporting a CFS diagnosis. It was observed that 1.63 present of the sample of adult Canadians reported a CFS diagnosis, a percentage that falls within the spectrum of findings previously documented in the literature (i.e., between 0.2-2.6 percent of the population) [10,39]. It was further observed that individuals with CFS were significantly more likely to be female, between the ages of 45-64, living alone, and to divorced or separated compared to individuals without CFS. However, they were equally as likely to be white/racial minorities as individuals without CFS. Relative to previous literature, the current findings corroborate other observations in that women are significantly more likely to have a diagnosis of CFS [11,12], and that the distribution of race is comparable in groups with and without a CFS diagnosis [16].
With respect to socioeconomic factors, it was revealed that adult Canadians with CFS were significantly more likely to be without employment or unable to work, and to have a personal income less than $20,000, findings similar to other studies [e.g., 10,39,40]. Taken together, it is unsurprising that individuals with CFS were more likely to report having difficulty meeting household expenses, and while they were more likely to have achieved less than secondary school education, they were also relatively as likely to have post-secondary graduation as individuals without CFS. Notwithstanding, such findings reflect the severity of disability experienced by individuals with CFS, as they are not able to maintain full-time, or in many cases any, employment due to their health status.

Mental health characteristics.
In terms of psychiatric diagnoses, it was observed that respondents reporting a CFS diagnosis were more likely to have a lifetime and 12-month diagnosis of MDD, GAD, and substance dependence, as well as lifetime alcohol dependence.
Further, CFS respondents were also more likely to report ADHD, PTSD, and having experienced childhood maltreatment in the form of physical and sexual abuse. These findings are all consistent with the existing body of literature, where individuals with CFS have been found to present with significantly greater prevalence rates of psychiatric diagnoses, including mood disorders, histories of childhood trauma, PTSD, and ADHD [2,25,26,27,29,32,33,34].

Clinical Implications
The discrepancies in socioeconomic status between adults with CFS and those without certainly have implications for general health status and well-being. For instance, since low socioeconomic status per se, is often associated with poorer health behaviours, particularly in terms of unhealthy dietary realities [e.g., 41], sedentary behaviour, healthcare interactions, and treatment adherence [e.g., 42,43], such are certainly considerations when advocating for the optimal health of those with CFS. In addition, given significant activity limitations already experienced by individuals with CFS, it is possible that the likelihood of lower socioeconomic status could further exacerbate poor health outcomes already characteristic of this population.
Lower socioeconomic status could also limit accessibility to health care services and various treatment options, as the financial realities of CFS sufferers also limit access to private sector services.
The fact that individuals with CFS are much more likely to live alone, and report being divorced or separated has also been linked with potential negative health consequences.
Specifically, individuals who live alone are more likely to experience cardiac issues, mental health challenges, and even instances of higher mortality in younger age cohorts [44,45].
Further, it is feasible that living alone is indicative with one's sense of social isolation, with compromised access to often limited social networks which could certainly relate with poorer health outcomes [46,47]. As a result, future research should explore the potential health status influence that social contextual factors, such as social support, might play in the life of CFS sufferers.
Based on socioeconomic conditions alone, while it is clear that physical and behavioural concerns are quite likely, they are not to only piece of the CFS health-status puzzle. Indeed, as clearly documented in the present study, the notably high instances of psychiatric disorder diagnoses associated with CFS sufferers, including MDD, GAD, and substance dependence certainly complicate and exacerbate concerns over CFS sufferer wellbeing. Such findings speak to the importance of considering CFS as more than simply a set of physical symptoms in need of treatment, but also examining psychological components of symptomology and how psychological intervention may aid in alleviating symptomology [20].
The relatively high prevalence of reported PTSD and childhood maltreatment are quite striking and troubling in terms of their link with CFS. From a theoretical perspective, it is interesting to note that PTSD has been associated with a concept referred to as disorganized attachment [48]. Approximately 82 percent of children who have experienced maltreatment demonstrate disorganized attachment [49], such that they have develop a negative view of both the self and others [50], which has been further linked to lower social competence, decreased reliance on others, lower romantic involvement, and hostility in romantic relationships [50,51].
Perhaps an indication of this might be evident in the findings herein with a higher prevalence of those with CFS living alone, and reporting being divorced or separated than individuals without CFS. Again, future research involving explorations of social factors, including distinctive relationship characteristics seems very well justified.

Limitations
While the findings of the present study provide insight into a better understanding of the CFS population as a whole, and many challenges experienced, there are several limitations to acknowledge. Firstly, the CCHS-MH sample excluded a small percentage of the population, including individuals living on Aboriginal settlements, members of the Canadian forces, and individuals that are institutionalized this limiting the generalizability of the results. Secondly, since study relied on the self-report of a CFS diagnosis by a health professional, there was no way to verify either the diagnosis, or the particular health profession providing the diagnosis.
Thirdly, since participants were asked whether they had been diagnosed with CFS, there is also a chance of underreporting whereby those living CFS, but not diagnosed were excluded.
Further, with secondary data analysis are limitation in the examination and interpretation of certain variables, such as childhood maltreatment as the measure used does not capture emotional abuse or neglect which has similar implications for physical and psychological functioning as compared with physical abuse or neglect, sexual abuse, and witnessing violence [52,53].

Conclusions
The results of this study have important implications for the research into, and treatment of individuals with CFS. The socioeconomic realities appear to reflect the severity of illness and poor health status of this population. Further, living alone, or being without partnership, suggests a high likelihood of social isolation, and perhaps a sense of feeling misunderstood about their illness which also may provide some insight into well-documented stigma in the literature, and mental health difficulties experienced by this population. Indeed, deficiencies in social support seem quite likely, and worthy of investigation especially given the high prevalence of childhood maltreatment histories, and comorbidity of PTSD, MDD, and GAD.

Declarations
 Ethics approval for this study was not required as data were extracted from a publically   Acknowledgements -Not applicable.