Prevalence of Gastrointestinal Symptoms and Irritable Bowel Syndrome Among Individuals With Symptomatic Posttraumatic Stress Disorder

Abstract

Goals: 

Our aim was to describe the prevalence of irritable bowel syndrome (IBS) and other gastrointestinal symptoms in a sample of veterans with posttraumatic stress disorder (PTSD) and to examine the relationship between gastrointestinal symptoms, PTSD severity, depression severity, and number of prior traumatic events reported.

Background: 

IBS and PTSD can co-occur; yet, little research has focused on describing the gastrointestinal symptoms and prevalence of IBS among veterans with PTSD.

Materials and Methods: 

We examined baseline data from a randomized clinical trial of behavioral interventions for veterans with PTSD. Veterans completed questionnaires assessing gastrointestinal symptoms (Gastrointestinal Patient-Reported Outcome Measures Information Systems; PROMIS) and lifetime traumatic events. Multivariable regression analyses were performed to examine associations between gastrointestinal symptoms and the number of prior traumas reported PTSD severity, and depression symptom severity.

Results: 

One hundred eighty-four veterans with a diagnosis of PTSD were included. Twenty-five percent met the Rome III criteria for IBS. Veterans reported gastrointestinal symptoms including abdominal/belly pain (36%), diarrhea (21%), constipation (18%), and bloating/gas (17%). In multivariable analyses, greater PTSD severity was associated with worse constipation (P=0.008), diarrhea (P=0.005), and gas/bloating (P=0.001) when controlling for age and sex. Higher levels of depressive symptoms severity were associated with greater abdominal/belly pain (P=0.04).

Conclusions: 

Among a sample of veterans with PTSD, rates of IBS and abdominal/belly pain are greater than general US population reference values. Although levels of constipation and bloating/gas are lower than general US population reference values, increased severity of PTSD was associated with increased gastrointestinal symptoms.

Irritable bowel syndrome (IBS) is a symptom-based syndrome characterized by abdominal pain and altered bowel habits that affects around 6% to 17% of the world population.¹ Estimates of IBS prevalence vary due to geographical differences and confounders such as diagnostic criteria and research methodology.¹ IBS is known as a disorder of gut-brain interaction due to dysregulation of the gut-brain axis which can be related to central and peripheral mechanisms and results in significant health care expenditures and reductions in health-related quality of life.^2–4 Patients with IBS also commonly meet criteria for psychiatric conditions, such as major depression, posttraumatic stress disorder (PTSD), and generalized anxiety disorder.⁴

Psychological factors, including daily life stress and fear of physical symptoms and their potential consequences, predict both the onset and severity of IBS symptoms.⁵ Multiple studies also report an association between psychological, physical, or sexual trauma and diagnosis of IBS,^4,6–8 which is reported by ∼35% to 50% of patients with IBS^4,7,9; such trauma exposure is associated with more severe IBS symptoms and lower functional status.⁹ Although most studies have focused on childhood trauma and abuse, other studies support an association between gastrointestinal (GI) symptoms and trauma when trauma is experienced later in life.^9,10 For example, deployment to a war zone and combat exposure have been found to be associated with an increased risk of functional GI disorders, including IBS and functional dyspepsia.^4,11 Among the subset of individuals with trauma exposure who develop PTSD, epidemiologic studies indicate that PTSD and IBS are often comorbid,¹² especially among veterans^13–15 and an incident diagnosis of PTSD appears associated with an increased risk of developing IBS (standardized incidence ratio of 1.8 as compared with the general population).¹⁶

As described above, much of the literature on the association between trauma and GI symptoms has focused on whether patients meet criteria for IBS and has emphasized pain severity,^{4,13–15,17,18} whereas the relationship between trauma (or PTSD) and a broader range of GI symptoms, such as bloating, constipation and diarrhea has received less study. In addition, the relationship between PTSD or depression severity, the number of traumatic events reported, and GI symptom severity has not been well-studied. In terms of the multiplicity of traumas as a risk factor for more frequent or more severe GI symptoms, one study found that IBS patients who reported multiple forms of abuse had worse IBS symptoms and lower health-related quality of life compared with IBS patients who reported 1 or 0 types of abuse.⁴ Many veterans with PTSD have suffered multiple forms of trauma, which often includes combat-related trauma as well as sexual abuse.^19,20 Given that IBS occurs with increased frequency among those with PTSD, as well as the recognition that patients can also experience bothersome symptomatology without meeting criteria for IBS, further study of the prevalence, spectrum, and severity of GI symptomatology among veterans with PTSD could help to guide the clinical care of this population.

The purposes of this study were to describe the prevalence of IBS as well as symptoms of gaseousness/bloating, constipation, diarrhea, and abdominal (belly) pain in a sample of veterans with PTSD. We also compared GI symptoms to norms from the US population and examined the relationship between GI symptoms and the number of prior traumas reported PTSD severity and depression symptom severity.

MATERIALS AND METHODS

Study Design and Sample

We conducted an analysis of baseline data from a randomized clinical trial comparing 2 behavioral interventions for veterans with PTSD.²¹ Veterans with a diagnosis of PTSD were recruited from VA Puget Sound Health Care System through mailings. A telephone screener was used to assess eligibility. Full inclusion and exclusion criteria can be found in the primary study manuscript.²¹ Briefly, the primary inclusion criterion was veterans who met the Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition (DSM-5) criteria for PTSD for any reason (ie, not limited to combat-related trauma). Veterans were excluded if they met any of the following criteria: substance use dependence disorder other than alcohol, alcohol use that posed a safety concern, high risk of suicide, psychotic disorder, mania, diagnoses of borderline or antisocial personality disorder documented in the electronic health record, or a psychiatric admission in the past month.

Instruments

A diagnosis of IBS was assessed by the Rome III questionnaire, which assesses criteria over the past 12 weeks. GI symptoms were measured using the GI-PROMIS scales for diarrhea (5 items), constipation (9 items), belly pain (6 items), and gas/bloat/flatulence (12 items).²² The PROMIS GI symptom scales are system targeted rather than disease targeted and are appropriate to measure a range of GI symptoms and related distress among individuals both with and without IBS; symptoms occurring over the past week are assessed.²² Past month PTSD severity was assessed using the 30-item Clinician-Administered PTSD Scale for DSM-5 (CAPS-5) (range: 0 to 80) structured interview.²³ A higher score indicates a greater severity of PTSD. It has high internal consistency (α=0.88), high interrater reliability (intraclass correlation coefficient=0.91), and good test-retest reliability (intraclass correlation coefficient=0.78).²³ CAPS-5 interviews were performed by an experienced clinician. Five percent of CAPS-5 interviews were reviewed by another experienced clinician during the conduct of the study to assure accuracy. Depression in the past week was assessed using the NIH Toolbox sadness measure, which is identical to the NIH PROMIS depression measure.²⁴ The depression scale was scored on a T-score metric with a mean of 50 and SD of 10 in the general population. A higher score indicates a greater severity of depression. Demographic characteristics recorded were age, sex, race, ethnicity, marital status, education, and prior history of mental health inpatient admission. The number and type of prior traumas experienced was assessed with the Life Events Checklist for DSM-5, a self-report measure to screen for traumatic events.²⁵ Scores range from 0 to 17 events.

Statistical Analysis

All analyses were performed using Stata 16.1 software (StataCorp LLC, College Station, TX). PROMIS measures were scored using the Health Measures scoring service, which scores items on a T-score metric to enable comparisons with general US population reference values (mean=50, SD=10). Percentiles were calculated based on published literature.²⁶ Descriptive statistics were calculated using means and SDs for continuous variables and number and percentages for categorical variables. The Pearson correlations were used to examine the relationship between individual GI symptoms and the number of prior traumas reported PTSD severity, and depression symptom severity. Point-biserial correlations were used to examine the relationship between individual GI symptoms and IBS status. Separate linear regression models were built with each of the GI symptoms (abdominal/belly pain, constipation, diarrhea, gas/bloating) as the dependent variable and number of prior traumas reported, PTSD severity, and depression symptom severity as independent variables, controlling for age and gender. P-values <0.05 were considered statistically significant.

RESULTS

Demographic Characteristics

Baseline characteristics were obtained on 184 veterans with a clinical diagnosis of PTSD (Table 1). The mean age of veterans was 57.1 (SD=13.1). The majority of veterans were male (83.1%). Veterans had a mean PTSD severity of 35.5 (SD=11.8) and a mean PROMIS depression T-score of 60.9 (SD=7.9).

TABLE 1 - Demographics of Individuals With Symptomatic PTSD (N=184)

Demographics	n (%)
Age [mean (SD)]	57.1 (13.1)
No. prior traumas (range: 2-17) [mean (SD)]	11.6 (3.6)
PTSD severity (CAPS-5) [mean (SD)]	35.5 (11.8)
PROMIS depression (T-score) [mean (SD)]	60.9 (7.9)
Sex
Male	153 (83.2)
Female	30 (16.3)
Transgender	1 (0.5)
Race
African American	49 (26.6)
Asian American	4 (2.2)
Native American	16 (8.7)
Pacific Islander	2 (1.1)
White	117 (63.6)
Other	9 (4.9)
Ethnicity
Hispanic/Latino	8 (4.9)
Non-Hispanic/Latino	157 (95.6)
Marital status
Never married	30 (16.5)
Married or permanent partnership	88 (48.4)
Separated	7 (3.9)
Divorced	46 (25.3)
Widowed	9 (5.0)
Other	2 (1.1)
Education
Less than 12th grade education	4 (2.2)
High school graduated or GED	20 (10.9)
Some college	81 (44.0)
College graduate	46 (25.0)
Postgraduate studies	33 (17.9)
Prior mental health or SUD inpatient admission	74 (40.2)

CAPS-5 indicates clinician-administered PTSD Scale; GED, general educational development; PTSD, posttraumatic stress disorder; SUD, substance use disorder.

Prevalence of IBS and GI Symptoms

Among veterans in the sample, 25% met Rome III criteria for IBS (n=46). Of those who met the criteria for IBS, subtypes included 37% constipation, 37% diarrhea, 24% mixed, and 2% unclassified. Within the sample, 36.7% (n=11) female veterans met Rome III criteria for IBS, and 22.9% (n=35) of male veterans met Rome III criteria for IBS, a difference that did not reach statistical significance (P=0.11). Veterans reported a variety of GI symptoms (Fig. 1) including abdominal/belly pain (35.7%), diarrhea (21%), constipation (18.2%), and bloating/gas (17%). Table 2 reports the PROMIS T-scores which are normed to a general US population of persons who reported at least 1 GI symptom.

FIGURE 1: Prevalence of individual gastrointestinal symptoms in the past week among individuals with symptomatic posttraumatic stress disorder.

TABLE 2 - PROMIS GI Symptoms Among Individuals With Symptomatic Posttraumatic Stress Disorder

PROMIS GI Symptoms	T-score	SD
Abdominal/belly pain (n=128)	53.5	12.2
Constipation (n=168)	48.2	9.8
Diarrhea (n=167)	50.4	9.1
Gas/bloating/flatulence (n=152)	47.8	10.5

T-scores are normed to the general US population who has reported at least 1 GI symptoms, with a mean of 50 and SD of 10.

GI indicates gastrointestinal; PROMIS, patient-reported outcome measures information system.

To further aid in interpretation, Table 3 reports PROMIS T-scores based on categories of within normal limits (T-score <50), mild (T-score 55 to 60), moderate (T-score 60 to 70), and severe (T-score 70+). For abdominal/belly pain, 47.2% were within normal limits, 22.1% mild, 24.4% moderate, and 6.3% severe abdominal/belly pain.

TABLE 3 - Severity of PROMIS GI Symptoms Among Individuals With Symptomatic Posttraumatic Stress Disorder

PROMIS GI Symptoms	n (%)
Abdominal/belly pain
Within normal limits	60 (47.2)
Mild	28 (22.1)
Moderate	31 (24.4)
Severe	8 (6.3)
Constipation
Within normal limits	125 (74.4)
Mild	23 (13.7)
Moderate	18 (10.7)
Severe	2 (1.2)
Diarrhea
Within normal limits	111 (66.5)
Mild	33 (19.8)
Moderate	21 (12.6)
Severe	2 (1.2)
Gas/bloating
Within normal limits	105 (69.1)
Mild	26 (17.1)
Moderate	20 (13.2)
Severe	1 (0.7)

Relationship Between Number of Prior Traumas Reported, PTSD Severity, and Depression Symptom Severity With GI Symptoms

Table 4 presents correlations between number of prior traumas reported, PTSD severity, and depression symptom severity with GI symptoms. Severity of PTSD was significantly associated with each of the GI symptoms of abdominal/belly pain (r=0.29, P<0.01), constipation (r=0.28, P<0.01), diarrhea (r=0.26, P<0.01), and gas/bloating (r=0.32, P<0.01) as well as meeting the criteria for IBS (r=0.28 P<0.01). Number of prior traumas was associated with gas/bloating (r=0.18, P=0.03) and meeting criteria for IBS (r=0.18, P=0.03). Depression symptom severity was associated with GI symptoms of abdominal/belly pain (r=0.3, P<0.01) and constipation (r=0.21, P<0.01) as well as meeting criteria for IBS (r=0.15, P=0.04).

TABLE 4 - Correlation of Number of Prior Traumas, PTSD Severity, and Depression Symptom Severity With Gastrointestinal Symptoms

GI Symptoms	No. Prior Traumas	PTSD Symptom Severity	Depression Symptom Severity
Abdominal/belly pain	0.17	0.29*	0.33*
Constipation	0.11	0.28*	0.21*
Diarrhea	0.08	0.26*	0.14
Gas/bloating	0.18*	0.32*	0.12
Met criteria for IBS	0.23*	0.28*	0.15*

^*P<0.05.

IBS indicates irritable bowel syndrome; PTSD, posttraumatic stress disorder.

Multivariable Analysis

In the multivariable regression analysis (Table 5), after adjusting for age and sex, those with higher levels of depressive symptom severity had greater abdominal/belly pain (P=0.04). After adjusting for age and sex, those with higher levels of PTSD severity had greater levels of constipation (P=0.008), diarrhea (P=0.005), and gas/bloating (P=0.001). Those with higher levels of PTSD severity (odds ratio: 1.05, P=0.013) and a higher number of prior traumas (odds ratio: 1.14, P=0.04) were more likely to meet the criteria for IBS, adjusting for age and sex.

TABLE 5 - Multivariable Regression of Number of Prior Traumas, PTSD Severity, and Depression Symptom Severity With Gastrointestinal Symptoms Controlling for Age and Sex

GI Symptoms	Regression Coefficient (95% Confidence Interval)	P
Abdominal/belly pain*
No. prior traumas	0.11 (−0.52, 0.74)	0.74
PTSD severity	0.12 (−0.1, 0.33)	0.29
Depression symptom severity	0.39 (0.03, 0.75)	0.04
Constipation*
No. prior traumas	0.1 (−0.35, 0.55)	0.67
PTSD severity	0.22 (0.06, 0.37)	0.008
Depression symptom severity	0.07 (−0.17, 0.31)	0.57
Diarrhea*
No. prior traumas	−0.04 (−0.47, 0.38)	0.85
PTSD severity	0.21 (0.07, 0.36)	0.005
Depression symptom severity	−0.04 (−0.27, 0.19)	0.74
Gas/bloating*
No. prior traumas	0.17 (−0.31, 0.66)	0.48
PTSD severity	0.29 (0.11, 0.46)	0.001
Depression symptom severity	−0.16 (−0.41, 0.09)	0.22
	Odds ratio (95% confidence interval)	P
Met criteria for IBS*
No. prior traumas	1.14 (1.01, 1.28)	0.04
PTSD severity	1.05 (1.01, 1.09)	0.013
Depression symptom severity	0.99 (0.94, 1.05)	0.85

Bold value indicates statistical significance, P<0.05.

^*Adjusting for age and sex.

IBS indicates irritable bowel syndrome; PTSD, posttraumatic stress disorder.

DISCUSSION

Among a sample of veterans with PTSD, the percentage reporting abdominal/belly pain (35.7%) was greater than reported in a nationally representative survey of the US population, which found abdominal pain in 24.8% of the sample in the past week.²⁶ This is further exemplified by the high rate of IBS among veterans with PTSD. Our study reported a prevalence of 25% meeting Rome III IBS criteria which is higher than the prevalence in the United States.²⁷

In our sample, 37% of female veterans met the criteria for IBS, which aligns with previous research. A prior survey of 337 female veterans found that 33.5% met the criteria for IBS,²⁸ and another survey of 248 women veterans showed an IBS prevalence of 38%,¹⁸ consistent with the high rate found in our study among female veterans, in particular. Females in our study, although all have the IBS risk factor of PTSD, have similar IBS rates to those found in samples of women veterans that presumably include both those with and without PTSD. This lack of difference could be due to the use of Rome III criteria in the current study, whereas Rome II was used in the previous studies. Alternatively, although it is not clear how potential study participants were approached in other studies, recruitment materials and methods for studies focused on IBS could disproportionately attract more women experiencing such symptoms, whereas our study focused recruitment on PTSD. Additional research is needed to better understand the relationship between PTSD and IBS.

Rates of constipation, diarrhea, and bloating/gas in our study were similar to those reported in a Nationally Representative Survey in the United States, which found rates of 19.7%, 20.2%, and 20.6% over the past week, respectively.²⁶ In our sample, T-score values for constipation (mean=48, SD=10) and bloating/gas (mean=48, SD=11) were slightly lower than the general US population reference values (mean=50, SD=10) since those reporting constipation and gas/bloating had mild symptom severity. Although other studies have reported the prevalence of PTSD among patients with IBS,^12,29 few studies have reported on the prevalence of IBS among patients with PTSD. The high prevalence of IBS in our sample of veterans with PTSD is consistent with the results of a large meta-analysis (involving 648,375 subjects in 8 studies) which found that PTSD is a significant risk factor for IBS with a pooled odds ratio of 2.8.¹⁷ The evidence that PTSD is associated with an excess risk of IBS adds to a broader literature indicating that PTSD is associated with higher rates of other health problems, including coronary artery disease, asthma, and arthritis.^30,31

Among individuals with PTSD, we did not find an association between number of traumas and GI symptoms, which differs from the findings of a study of IBS patients that found that multiple forms of abuse was associated with worse IBS symptoms.⁴ The difference in findings could be accounted for by the difference in patient populations and the type and method of symptom assessment—Kanuri and colleagues studied a predominantly female population and assessed symptoms of IBS, whereas our population was predominantly male, and we assessed a range of symptoms not limited to IBS. A study among female veterans found multiple forms of abuse were associated with the presence of IBS but did not specifically assess the association between cumulative number of traumas reported and IBS symptoms.²⁸ A meta-analysis of trauma and functional somatic syndromes, including IBS, identified the type of trauma as a moderating variable.³²

Our findings suggest that among veterans with symptomatic PTSD, those veterans with increased severity of PTSD may be at an elevated risk of experiencing mild or moderate GI symptoms including abdominal/belly pain, constipation, diarrhea, and gas/bloating. Furthermore, our findings indicate that increased PTSD severity may further exacerbate these symptoms among veterans. Thus, clinicians caring for veterans with PTSD should assess for GI symptoms and refer patients for appropriate care. Larger studies are needed to further characterize the prevalence of GI symptoms and IBS among veterans and nonveterans with PTSD using the updated Rome IV criteria and incorporating additional GI symptom measures such as bowel incontinence, disrupted swallowing, heartburn/reflex, and nausea/vomiting. Furthermore, research is needed to determine if interventions addressing PTSD symptoms can also assist in reducing GI symptoms.

Limitations of the study include a relatively modest sample size that was predominantly male. Analyses of the number of traumas reported may also be subject to recall bias. Individuals participating in the randomized control trial may not be representative of veterans with PTSD in general or nonveterans with PTSD. Study recruitment occurred before the Rome IV criteria were published, and veterans may be classified differently if the Rome IV criteria were used. In addition, since the study was focused on PTSD, a history of other GI conditions was not obtained. Despite these limitations, this study provides valuable preliminary information regarding the role of severity of PTSD symptoms in increasing GI symptoms.

This is one of the first studies to report on the prevalence of IBS and GI symptoms among veterans with PTSD with findings indicating that rates of IBS and abdominal/belly pain are greater than the general population. Although levels of diarrhea, constipation, and bloating/gas are similar to the general population, increased severity of PTSD and depressive symptoms was associated with increased GI symptom severity.