Assessing comorbid PTSD, depression, and anxiety in fibromyalgia patients: a retrospective observational study

Abstract

Background

Fibromyalgia frequently coexists with psychiatric disorders, creating complex challenges in managing the health and quality of life for affected individuals. Existing literature points to significant overlap between fibromyalgia and conditions like posttraumatic stress disorder (PTSD), anxiety, and depression, but no large-scale analysis within a single American healthcare system has yet been conducted.

Methods

This retrospective observational study analyzed 1,516 fibromyalgia patients from HCA Healthcare facilities from January 1, 2022, to December 31, 2023, including only patients aged 18 and older with at least one psychiatric comorbidity. Chi-square tests examined associations between psychiatric outcomes (PTSD, depression, anxiety) and demographic factors such as age, sex, and race. Hospital length of stay (LOS) was analyzed among comorbidity groups using the Kruskal–Wallis test, with Bonferroni correction applied for pairwise comparisons.

Results

The sample had a mean age of 52.2 years, was predominantly female (95.98%) and white (77.51%). Anxiety (61.02%) and depression (39.75%) were highly prevalent, while PTSD was less common (8.64%). Significant age differences emerged. Younger patients had more PTSD than those 65 + years old. Those 30–39 years old had the highest PTSD prevalence. Conversely, the prevalence of depression increased with age, peaking in the 65 + years old group. Anxiety was more prevalent in the middle-aged patients, peaking in the 40–52 years old group. White patients and nonwhite patients did not have significant differences in PTSD, anxiety, or depression prevalence. Sex differences were significant for anxiety only (p = .028), showing higher rates among females (62% in females versus 48% in males). Mean LOS was 1.93 days, with significant differences across comorbidity groups (p = < .0001). Pairwise comparisons revealed that patients with only anxiety tended to have significantly shorter LOS than patients with only depression and with two psychiatric comorbidities (p < .001).

Conclusions

Psychiatric comorbidities are highly prevalent in hospitalized fibromyalgia patients and influence hospitalization outcomes. Anxiety, depression, and PTSD demonstrate unique relationships with age. The presence of multiple psychiatric comorbidities is associated with longer hospital stays, highlighting the need for integrated care approaches.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12888-025-06708-4.

Background

Fibromyalgia often coexists with psychiatric disorders, forming a complex web of symptoms and challenges for those affected. The relationship between fibromyalgia and psychiatric conditions has been a subject of research and clinical interest, shedding light on the interplay between physical and mental health.

Amir et al. [1] explored the connection between fibromyalgia and posttraumatic stress disorder (PTSD), as well as tenderness [1]. Their study revealed a significant association between PTSD and fibromyalgia, suggesting that trauma and stress can contribute to the development or exacerbation of fibromyalgia symptoms. Moreover, the presence of tenderness, a hallmark of fibromyalgia, was also linked to PTSD, indicating a potential overlap in physiological responses and sensitivities. The systematic review by Kleykamp et al. [2] delved into the prevalence of psychiatric comorbidities in fibromyalgia, drawing from a comprehensive analysis. They found a high prevalence of psychiatric disorders such as anxiety, depression, and PTSD among individuals with fibromyalgia [2]. This underscores the importance of addressing not only the physical symptoms but also the psychological well-being of patients with fibromyalgia to provide comprehensive care. Buskila and Cohen [3] highlighted the comorbidity of fibromyalgia with various psychiatric disorders beyond PTSD. Their review encompassed conditions like major depressive disorder, generalized anxiety disorder, and somatoform disorders [3].

The overlap between fibromyalgia and these psychiatric conditions suggests shared pathophysiological mechanisms or a bidirectional relationship where one condition can influence the other, leading to a more complex clinical presentation. A large-scale retrospective study from a single hospital system has not been conducted to our knowledge at the time of this writing.

The objectives of this retrospective observational study were to describe the demographic, psychiatric, and medical characteristics of hospitalized fibromyalgia patients, to evaluate the prevalence of psychiatric comorbidities and their relationship with demographic factors, and to investigate the impact of psychiatric comorbidities on hospitalization metrics, particularly length of stay, to better understand how psychiatric comorbidity may affect hospitalization outcomes and healthcare resource allocation.

Methods

This study examined fibromyalgia patients across Healthcare Corporation of America (HCA) Healthcare facilities from January 1, 2022, to December 31, 2023. This study was a retrospective observational analysis utilizing data extracted from hospitalized patients diagnosed with fibromyalgia. Data were collected from HCA database electronic medical records, including demographic information, psychiatric comorbidities, and hospitalization metrics such as length of stay (LOS). The following variables were obtained from patient medical records: demographic information (age, sex, race/ethnicity), psychiatric comorbidities (post-traumatic stress disorder [PTSD], depression, and anxiety), and hospitalization metrics such as length of stay (LOS). For each psychiatric comorbidity, diagnostic codes consistent with ICD-10 criteria, as these are used for billing, were used to ensure accuracy, that is, PTSD (F43.10–12), depression (F32, F33), or anxiety (F41). Length of stay was recorded in days, including mean, median, and standard deviation. These variables were chosen based on their clinical relevance and hypothesized association with severity of disease and outcomes in fibromyalgia patients along with intensity of resources needed for treatment.

Fibromyalgia was defined based on the American College of Rheumatology (ACR) 2016 criteria, which require the presence of widespread pain lasting more than three months, not explained by another medical condition, along with accompanying symptoms such as fatigue, sleep disturbances, and cognitive difficulties (often referred to as "fibro fog"). The diagnosis was documented in the electronic health records by clinicians based on these criteria and supported by patient history and physical examination findings. All patients included in this study were admitted to inpatient services at HCA Healthcare hospitals. These facilities employ a multidisciplinary approach to patient care, involving internal medicine teams, specialty services (e.g., rheumatology and psychiatry), and allied health professionals such as occupational therapists (OT) and physical therapists (PT). Inclusion criteria were patients aged 18 years and older with fibromyalgia listed among their top three diagnoses and at least one psychiatric-related condition, that is, PTSD (F43.10–12), depression (F32, F33), or anxiety (F41). This yielded 1647 patients, but 131 were removed to keep one patient encounter for each patient. We restricted the analysis to the first hospital encounter for each patient to eliminate confounding effects of multiple admissions by the same individual, which might otherwise skew the results for variables such as length of stay. As such, the total sample size was 1,516 patients.

Data analysis began with a descriptive overview of all variables, including demographics, comorbidities, and the top 30 diagnosis codes associated with fibromyalgia. Chi-square tests were then employed to examine associations between categorical variables, specifically analyzing outcomes (PTSD/Depression/Anxiety) by age group, race (White vs. Non-White), and sex (Male vs. Female). For significant chi-square results, pairwise comparisons were conducted to identify specific group differences, with Bonferroni corrections applied to adjust p-values for multiple comparisons.

To analyze differences in hospital length of stay (LOS) among comorbidity groups, the Kruskal–Wallis test was used due to the non-parametric nature of the data. Following significant Kruskal–Wallis test results, post-hoc pairwise comparisons were performed, again applying Bonferroni corrections to adjust p-values. Throughout the analysis, a p-value of less than 0.05 was considered statistically significant.

Results

Patient demographics and clinical characteristics

A total of 1,516 patients with fibromyalgia were included in the analysis. The mean age of the cohort was 52.24 years (SD = 14.62), with the largest age group being 40–52 years (33.58%) (Table 1). The majority of patients were female (95.98%) and white (77.51%) (Table 1). Among psychiatric comorbidities, anxiety was the most prevalent (61.02%), followed by depression (39.75%) and post-traumatic stress disorder (PTSD) (8.64%) (Table 1). In terms of comorbidity groupings, the most common category was anxiety alone (40.63%), followed by two-condition comorbidities (20.98%) and depression alone (19.26%) (Table 1). The mean length of hospital stay was 1.93 days (SD = 4.84), with a median of 1 day (IQR: 0–2 days) (Table 1).

Table 1.

Descriptive statistics for fibromyalgia patient demographics, comorbidities, and clinical characteristics

Variable	Category	N (total N = 1516)	(%)
Age Group	18–29	92	(6.07%)
	30–39	194	(12.80%)
	40–52	509	(33.58%)
	53–64	391	(25.79%)
	65 +	330	(21.77%)
Sex	Female	1455	(95.98%)
	Male	61	(4.02%)
Race	African American	123	(8.11%)
	Asian	9	(0.59%)
	Hispanic	3	(0.20%)
	Multiracial/Other	202	(13.32%)
	Native American	4	(0.26%)
	White	1175	(77.51%)
Race (Binary)	Non-White	341	(22.49%)
	White	1175	(77.51%)
PTSD	Yes, in top 3 diagnoses	131	(8.64%)
Depression	Yes, in top 3 diagnoses	595	(39.75%)
Anxiety	Yes, in top 3 diagnoses	925	(61.02%)
Comorbidities Group	None	213	(14.05%)
	PTSD only	62	(4.09%)
	Depression only	292	(19.26%)
	Anxiety only	616	(40.63%)
	Two conditions	318	(20.98%)
	Three conditions	15	(0.99%)
Summary Statistics	Mean (SD)	Median (IQR)
Age	52.24 (14.62)	52 (42–63)
Length of Stay (LOS)	1.93 (4.84)	1 (0–2)

Age was categorized into five groups, and other variables include mortality, sex, race, PTSD, depression, and anxiety diagnoses being amongst the top 3 diagnoses for the fibromyalgia patient. Comorbidities were grouped into five categories, including combinations of PTSD, depression, and anxiety. Summary statistics for age, length of stay (LOS), and the number of cases are reported as mean (standard deviation) and median (interquartile range). Percentages were calculated based on the total sample size (N = 1,516). The 40-52 years old age group was the largest, with a mean age of 52.24 years old, and the sample was predominantly female (95.98%) and white (77.51%). Anxiety was the most common comorbidity (61.02%), and the most common comorbidity grouping was anxiety alone (40.63%), followed by the two conditions group (20.98%). The mean length of stay was 1.93 days, with a standard deviation of 4.84 days

Comorbidities and associated diagnoses

The analysis of comorbidities revealed a high prevalence of chronic medical and psychiatric conditions among fibromyalgia patients. The most common co-occurring conditions included anxiety disorder, unspecified (46.17%), essential hypertension (30.54%), depression, unspecified (29.62%), gastroesophageal reflux disease (21.90%), and hyperlipidemia (18.60%) (Table 2). Other frequently observed conditions included chronic pain (16.36%), hypothyroidism (13.39%), and migraine (10.62%) (Table 2). Additionally, 15.50% of patients had a history of nicotine dependence, and 10.29% were receiving hormone replacement therapy. COVID-19 exposure was recorded in 12.60% of patients, and bipolar disorder, unspecified was diagnosed in 7.92% (Table 2).

Table 2.

Top 30 diagnosis codes associated with fibromyalgia patients

Rank	ICD-10 Code	Diagnosis	Prevalence (%)	N
1	M797	Fibromyalgia	100.00	1516
2	F419	Anxiety disorder, unspecified	46.17	700
3	I10	Essential (primary) hypertension	30.54	463
4	F32A	Depression, unspecified	29.62	449
5	K219	Gastro-esophageal reflux disease without esophagitis	21.90	332
6	E785	Hyperlipidemia, unspecified	18.60	282
7	G8929	Other chronic pain	16.36	248
8	Z87891	Personal history of nicotine dependence	15.50	235
9	E039	Hypothyroidism, unspecified	13.39	203
10	Z20822	Contact with and (suspected) exposure to COVID- 19	12.60	191
11	G43909	Migraine, unspecified, not intractable, without status migrainosus	10.62	161
12	Z79890	HORMONE REPLACEMENT THERAPY	10.29	156
13	E669	Obesity, unspecified	10.09	153
14	J45909	Unspecified asthma, uncomplicated	9.96	151
15	Z9049	Acquired absence of other specified parts of digestive tract	9.96	151
16	Z90710	Acquired absence of both cervix and uterus	9.70	147
17	F17200	Nicotine dependence, unspecified, uncomplicated	9.30	141
18	F411	Generalized anxiety disorder	8.77	133
19	F319	Bipolar disorder, unspecified	7.92	120
20	F4310	Post-traumatic stress disorder, unspecified	7.85	119
21	M1990	Unspecified osteoarthritis, unspecified site	7.78	118
22	Z7982	Long term (current) use of aspirin	7.52	114
23	E119	Type 2 diabetes mellitus without complications	7.19	109
24	J449	Chronic obstructive pulmonary disease, unspecified	7.12	108
25	G4700	Insomnia, unspecified	6.53	99
26	E6601	Morbid (severe) obesity due to excess calories	6.40	97
27	F17210	Nicotine dependence, cigarettes, uncomplicated	6.40	97
28	Z7984	LONG TERM (CURRENT) USE OF ORAL HYPOGLYCEMIC DRUGS	6.27	95
29	M069	Rheumatoid arthritis, unspecified	6.13	93
30	R0789	Other chest pain	6.13	93

This table presents the most common comorbidities and associated conditions in the 1,516 fibromyalgia patients, highlighting the complex nature of fibromyalgia, with high rates of psychiatric disorders, pain syndromes, and various chronic health conditions co-occurring with the primary fibromyalgia diagnosis. The five most common comorbidities were anxiety disorder, unspecified; essential (primary) hypertension; depression, unspecified; gastro-esophageal reflux disease without esophagitis; and hyperlipidemia, unspecified. The host of many of these illnesses, such as joint pains and other chronic pain, validates the diagnosis of fibromyalgia

Socio-demographic factors and psychiatric comorbidities

The prevalence of psychiatric comorbidities differed across age groups. PTSD was more prevalent in younger patients with a peak in the 30–39 age group (13.4%), whereas the prevalence of depression increased with age, peaking at 50% in the 65 + age group (Table 3). Anxiety was most common in middle-aged patients, with the highest prevalence (65.82%) in the 40–52 age group (χ² = 11.65, p = 0.020) (Table 3). No significant differences were found in PTSD (χ² = 0.58, p = 0.448), depression (χ² = 0.02, p = 0.883), or anxiety (χ² = 0.01, p = 0.906) prevalence between white and non-white patients (Table 3). However, male patients exhibited a significantly lower prevalence of anxiety (48%) compared to female patients (62%; χ² = 4.85, p = 0.028) (Table 3).

Table 3.

Relationship between socio-demographic factors and psychiatric comorbidities in fibromyalgia patients

Characteristic	Category (n)	PTSD (% Diagnosed)	Depression (% Diagnosed)	Anxiety (% Diagnosed)
Age Group		χ2 = 26.35, p < .0001*	χ2 = 26.37, p < .0001*	χ2 = 11.65, p = .020*
	18–29 (n = 92)	9.78%	29%	53.26%
	30–39 (n = 194)	13.4%	31%	60.31%
	40–52 (n = 509)	11.2%	37%	65.82%
	53–64 (n = 391)	7.93%	40%	61.64%
	65 + (n = 330)	2.42%	50%	55.45%
Sex		χ2 = 3.01, p = .083	χ2 = 0.62, p = 0.431	χ2 = 4.85, p = .028*
	Female (n = 1455)	8.4%	39%	62%
	Male (n = 61)	15%	34%	48%
Race		χ2 = 0.58, p = .448	χ2 = 0.02, p = 0.883	χ2 = 0.01, p = .906
	White (n = 1175)	8.9%	39%	61%
	Non-White (n = 341)	7.6%	40%	61%

This table shows the association of age, sex, and race with psychiatric comorbidities, including PTSD, depression, and anxiety, in fibromyalgia patients. The data highlight the predominance of female and white patients, high prevalence of anxiety and depression, and the complex nature of comorbidity patterns in this population. Chi-square test results indicate significant differences in the prevalence of PTSD (χ² = 26.35, p < .0001) and anxiety (χ² = 11.65, p = .020) and depression (χ² = 26.37, p = <.001) across age groups of fibromyalgia patients. Younger patients had more PTSD than those 65+ years old, with those 30-39 with the highest prevalence. Conversely, the prevalence of depression increased with age, peaking in the 65+ years old group. Anxiety was more prevalent in the middle-age patients, peaking in the 40-52 years old group. Chi-square test results indicate no significant differences in the percentages of PTSD (χ² = 0.58, p = 0.448), depression (χ² = 0.02, p = 0.883), or anxiety (χ² = 0.01, p = 0.906) between the two binary racial groups. Chi-square test results indicate no significant differences in the percentages of PTSD (χ² = 3.01, p = 0.083) or depression (χ² = 0.62, p = 0.431) between the two groups. However, male patients (48%) have a significantly lower prevalence of anxiety compared to female patients (62%; χ² = 4.85, p = 0.028)

^*Indicates statistical significance (p < .05)

Pairwise comparisons of PTSD, depression, and anxiety across age groups

Pairwise comparisons revealed significant differences in PTSD prevalence between older patients (65 + years, 2.42%) and younger age groups, with the highest rates observed in the 30–39 age group (13.4%, χ² = 22.5, p < 0.001) (Table 4). PTSD prevalence significantly declined with age. Similarly, the prevalence of depression was significantly higher in older patients (65 + years, 50%) compared to younger cohorts, particularly those aged 18–29 (29.4%, χ² = 11.56, p = 0.007), 30–39 (31.4%, χ² = 16.4, p < 0.001), and 40–52 (36.54%, χ² = 14.35, p < 0.001) (Table 4). Anxiety prevalence was significantly lower in the 65 + age group (55.45%) compared to the 40–52 age group (65.82%, χ² = 8.67, p = 0.032) (Table 4).

Table 4.

Pairwise comparisons of PTSD, depression, and anxiety prevalence among age groups of fibromyalgia patients

Age Group 1	PTSD %	Age Group 2	PTSD %	χ2	Adjusted p-value
18–29	9.78%	65 +	2.42%	8.262	0.041
30–39	13.40%	65 +	2.42%	22.491	< .0001
40–52	11.20%	65 +	2.42%	20.355	< .0001
53–64	7.93%	65 +	2.42%	9.548	0.020
Age Group 1	Depression %	Age Group 2	Depression %	χ2	Adjusted p-value
18–29	29.35%	65 +	50%	11.555	0.007
30–39	31.44%	65 +	50%	16.404	0.0001
40–52	36.54%	65 +	50%	14.353	0.0002
Age Group 1	Anxiety %	Age Group 2	Anxiety %	χ2	Adjusted p-value
40–52	65.82%	65 +	55.45%	8.665	0.032
(Other comparisons were not statistically significant after adjustment.)

Pairwise comparisons reveal significant differences in PTSD prevalence between patients aged 65+ (2.42%) and those aged 18–29 (9.78%, χ² = 8.26, p = .041), 30–39 (13.4%, χ² = 22.5, p = <0.001), 40–52 (11.2%, χ² = 20.36, p < .0001), and 53–64 (7.93%, χ² = 9.55, p = .020). The prevalence of PTSD decreases significantly with age, particularly among older patients aged 65+. Pairwise comparisons reveal significant differences in depression prevalence between patients aged 65+ (50%) and those aged 18–29 (29.4%, χ² = 11.56, p = .007), 30–39 (31.4%, χ² = 16.4, p = <0.001), and 40–52 (36.5%, χ² = 14.35, p = 0.0002). The prevalence of depression in fibromyalgia patients increases significantly with age, particularly among older patients aged 65+. Pairwise comparisons reveal significant differences in anxiety prevalence between patients aged 65+ (55.45%) and those aged 40–52 (65.82%, χ² = 8.67, p = .032). Chi-square test results suggest that older adults (65+) experience significantly lower anxiety prevalence compared to patients in middle age groups. Statistical significance was determined using chi-square tests with Bonferroni-adjusted p-values to account for multiple comparisons

Length of stay by comorbidity group

The length of hospital stay varied by comorbidity group. The Kruskal–Wallis test indicated a significant difference in hospital length of stay among distinct comorbidity groups (χ² (5) = 71.54, p < 0.0001) (Table 5). Pairwise two-sided multiple comparison analysis using the Dwass, Steel, Critchlow-Fligner Method showed that patients with only anxiety (Median = 0, IQR [0–1]) had a significantly shorter length of stay compared to those with only depression (Median = 1, IQR [0–2], p < 0.001) and those with two psychiatric comorbidities (e.g., depression and anxiety, or depression and PTSD, or anxiety and PTSD) (Median = 1, IQR [0–2], p < 0.001) (Table 5). Patients with no psychiatric comorbidities had a median length of stay of 1 day (IQR: 0–2), and those with PTSD alone had a median of 1 day (IQR: 0–3) (Table 5). The presence of multiple psychiatric comorbidities was associated with a longer hospital stay compared to having anxiety alone.

Table 5.

Hospital length of stay by comorbidity group for fibromyalgia patients

Comorbidity Group	N	Mean Length of Stay (SD)		Median Length of Stay (IQR)
No Comorbidities	213	2.32 (5.97)		1 (0–2)
PTSD Only	62	2.1 (3.63)		1 (0–3)
Depression Only	292	2.14 (4.67)		1 (0–2)
Anxiety Only	616	1.31 (3.69)		0 (0–1)
Two Comorbidities	318	2.64 (6.09)		1 (0–2)
Three Comorbidities	15	2.2 (3.34)		1 (0–2)
Kruskal–Wallis Test Results – Chi-Square: 71.54, p-value: < 0.0001
Pairwise Two-Sided Multiple Comparison Analysis – Dwass, Steel, Critchlow-Fligner Method
Comorbidity Groups Compared	Wilcoxon Z		DSCF Value	Adjusted P Value
Anxiety Only vs Depression Only	−5.1428		7.273	< .001
Anxiety Only vs Two Comorbidities	−8.1857		11.5763	< .001
All other comparisons were not statistically significant after adjustment

This table presents the hospital length of stay (LOS) for fibromyalgia patients by comorbidity group, analyzed using the Kruskal–Wallis test, indicating that hospital length of stay significantly differs among distinct comorbidity groups (${\chi }^2(5)$) = 71.54, p < .0001). Pairwise two-sided multiple comparison analysis of length of stay using the Dwass, Steel, Critchlow-Fligner Method showed that patients with only Anxiety (Median = 0, IQR [0–1]) tended to have significantly shorter length of stay than patients with only depression (Median = 1, IQR [0–2], p < .001) and with two categories of psychiatric disease, that is, depression and anxiety, or depression and PTSD, or anxiety and PTSD (Median = 1, IQR [0–2], p < .001)

Discussion

Consistent with prior research, our study demonstrates a high prevalence of anxiety (61.02%), depression (39.75%), and PTSD (8.64%) among fibromyalgia patients. This aligns with previous research highlighting the significant overlap between fibromyalgia and psychiatric disorders [4, 5]. The prevalence of PTSD (8.64%) is higher than general population estimates, supporting the association between trauma-related disorders and fibromyalgia [6].

Anxiety was the most frequently observed psychiatric comorbidity, particularly among middle-aged patients, whereas depression prevalence increased with age. PTSD, in contrast, was most prevalent among younger patients, with a notable decline in prevalence as age increased. These findings suggest that different psychiatric conditions may contribute uniquely to the disease presentation at different life stages, reflecting differences in life experiences, coping mechanisms, or reporting tendencies across age groups. Moreover, our findings align with existing literature suggesting that younger individuals with chronic pain conditions may experience heightened vulnerability to trauma-related disorders, potentially due to greater life stressors and earlier disease onset [7]. Anxiety may peak in middle-aged patients due to career or family responsibilities exacerbating their chronic pain. Conversely, as fibromyalgia patients age, they may be more likely to develop depression due to years of coping with chronic illness.

Additionally, the study population was predominantly female (95.98%), consistent with known fibromyalgia demographics. While no significant gender differences were found for PTSD or depression, females showed significantly higher rates of anxiety (62% vs. 48% in males). This gender disparity in anxiety prevalence warrants further investigation and may inform gender-specific treatment approaches. Nonetheless, there was a lack of significant differences in psychiatric comorbidities between white and non-white patients, but the predominance of white patients (77.51%) in the sample and inability to do subgroup racial analysis due to limited sample sizes may call for further research with more diverse populations to confirm these findings. While these findings may indicate comparable rates of psychiatric comorbidities across racial groups, underreporting or systemic barriers to diagnosis and care may obscure true disparities.

Patients with multiple psychiatric comorbidities experienced the longest hospital stays. This finding highlights the cumulative impact of mental health conditions on the complexity of care required for fibromyalgia patients. Given the interplay between chronic pain, PTSD, anxiety, and depression, patients with multiple comorbidities may require more extensive interventions, leading to prolonged hospitalizations and increased utilization of healthcare resources. These findings align with previous literature indicating that depression and PTSD are associated with increased healthcare costs and hospitalizations [8]. Anxiety alone, despite its high prevalence, may not necessitate extended inpatient care in the same way as depression or PTSD.

The top 30 diagnosis codes associated with fibromyalgia patients reveal a complex clinical picture, encompassing not only psychiatric disorders but also chronic pain conditions, sleep disorders, and metabolic issues. These comorbidities may exacerbate the intensity of fibromyalgia symptoms, impairing quality of life and complicating management. Moreover, the host of illnesses demonstrated in Table 2 validate the fibromyalgia diagnosis.

The high prevalence of mental health conditions among fibromyalgia patients could be attributed to multiple factors. Shared pathophysiological mechanisms, such as central sensitization and dysregulation of neurotransmitters like serotonin and dopamine, may contribute to both fibromyalgia and psychiatric disorders, leading to a higher co-occurrence of these conditions [9]. Additionally, chronic pain itself is a major risk factor for the development of anxiety, depression, and PTSD, as persistent pain can lead to emotional distress, social withdrawal, and impaired quality of life [10]. Individuals with fibromyalgia frequently experience sleep disturbances, fatigue, and cognitive dysfunction, all of which can exacerbate or trigger psychiatric symptoms. Additionally, psychosocial factors such as stress, adverse childhood experiences, and a history of trauma have been linked to both fibromyalgia and mental health disorders, further explaining their frequent co-occurrence [11]. These findings underscore the complex nature of fibromyalgia, and its impact on healthcare utilization calls for a multispecialty approach to fibromyalgia management.

Limitations and future directions

Several limitations must be acknowledged. The study relied on ICD-10 codes for diagnosis, which may introduce misclassification bias. Additionally, the cross-sectional nature of the analysis limits causal inferences regarding the relationship between psychiatric comorbidities and hospitalization metrics. Moreover, the study's retrospective nature and focus on a single healthcare system may limit its generalizability. Future research investigating the temporal relationship between fibromyalgia onset and the development of psychiatric comorbidities with longitudinal studies could provide valuable insights into disease progression and management strategies. Further, qualitative studies examining patient experiences with psychiatric care may provide deeper insights into unmet needs and barriers to effective treatment.

Abbreviations

PTSD

Post Traumatic Stress Disorder

LOS

Length of Stay

SD

Standard Deviation

CI

Confidence Interval

P

P-value (probability value)

Z

Z-score (standard score)

HCA

Hospital Corporation of America

F

ICD-10 codes for mental and behavioral disorders

Phi

Phi Coefficient (measure of association)

Cramer’s V

Measure of association strength

N

Sample size

Authors’ contributions

AR – Conceptualization, Methodology, Software, Validations, Formal Analysis, Investigation, Data Curation, Writing Original Draft, Review and Editing; JF – Review and Editing, Supervision.

Funding

HCA Healthcare and/or affiliated entities did not financially support this research work. There are no funders to report for this submission.

Data availability

The datasets used and/or analyzed during the current study are from the HCA Healthcare national database and available from the corresponding author on reasonable request.

Declarations

Ethics approval and consent to participate

The views expressed in this publication represent those of the authors and do not necessarily represent the official views of Hospital Corporation of America (HCA) Healthcare or any of its affiliated entities. Research was conducted with respect to principles of the Belmont Report and Declaration of Helsinki. This research was supported in whole or in part by HCA Healthcare and/or an HCA Healthcare affiliated entity. The views expressed in this publication represent those of the authors and do not necessarily represent the official views of HCA Healthcare or any of its affiliated entities.

This study protocol was reviewed and approved by HCA Healthcare PUBCLEAR (Project #24–1742) and determined to be non-human subject research. Ethics approval was waived, and Institutional Review Board (IRB) oversight was not required, as determined by the Centralized Algorithms for Research Rules on IRB Exemption (Submission ID #: 2024–519), in accordance with 45 CFR 46.102(e), which defines what constitutes human subjects research, which clarifies that this study does not involve "human subjects" as defined by U.S. federal regulations. Anonymized data were extracted from HCA Healthcare electronic health records for all initial encounters meeting the inclusion criteria. All patients had accepted the possibility of their results being de-identified prior to record creation.

Consent for publication

Not applicable.

Competing interests

The authors declare no competing interests.