IBS Is Strongly Associated With Generalized Anxiety Disorder

Abstract and Introduction

Abstract

Background No previous study has examined the comorbidity of Irritable Bowel Syndrome (IBS) and Generalized Anxiety Disorder (GAD) in a general population using standardized diagnostic methods.
Aim To examine the prevalence, comorbidity and risk correlates of IBS and GAD in a general population.
Methods A random community-based telephone survey was conducted. The questionnaire covered symptoms of IBS, GAD, core depressive symptoms, help-seeking behaviour and functional impairment on the Sheehan Disability Scale.
Results A total of 2005 participants completed the interview. The current prevalence of IBS was 5.4% and the 12-month prevalence of GAD was 4%. GAD was five times more common among IBS respondents than non-IBS respondents (OR: 5.84, P < 0.001), whereas IBS was 4.7 times more common among GAD respondents than among non-GAD respondents (OR: 6.32, P < 0.001). Core depressive symptoms (OR: 6.25, P < 0.01) and education level (OR: 5.918, P = 0.021) were risk correlates of GAD among IBS respondents. Comorbid respondents were more impaired than respondents having either disorder alone, but were not more likely to seek professional help than IBS-only respondents.
Conclusion Irritable Bowel Syndrome and GAD comorbidity was common and added to impairment in the community. The strong association between psychiatric morbidity and IBS observed in referral centres was not a consequence of increased help-seeking behaviour.

Introduction

Irritable Bowel Syndrome (IBS) is a common functional bowel disorder with a 12-month prevalence of about 20% in Western countries^[1] and 2–7% in Asian communities.^[2–4] It is typically a chronic and relapsing condition that is both distressing and disabling to its sufferers.^[5] Reasons for the chronicity and often unsatisfactory treatment response of IBS are complex, but may partly be mediated by undetected comorbid mental disorders.

Studies on the relationship between IBS and mental disorders are relatively few and often confined to referral centres. A clinical study which did not adopt Rome criteria for IBS reported a strong correlation between IBS symptoms and anxiety-depression in patients with recurrent depression.^[6] Another clinical study found that 94% of IBS patients had lifetime mental disorders.^[7] Specifically, the lifetime prevalence of generalized anxiety disorder (GAD), as defined by the Diagnostic and Statistics Manual of Mental Disorders, third edition revision (DSM-III-R),^[8] was 34% among these patients. As psychological distress could motivate individuals with IBS to seek treatment, the association between IBS and psychiatric disorders found in referral centres might inflate the degree of their association in the community because of selection bias. However, community-based studies of IBS and psychiatric disorders are limited. Using stratified random sampling, one general population study which did not adopt Rome criteria for IBS found that panic disorder and agoraphobia were found in 9.3% and 33.1% of people with IBS.^[3] Hazlett-Stevens et al.^[9] examined the relationship between IBS and GAD among college students rather than a general population. Nonetheless, they found that 21.5% of those with IBS had GAD compared to 7% of controls. These preliminary community studies suggest that there might be a significant association between IBS and anxiety disorders.

Of the different types of anxiety disorders, GAD may be particularly associated with IBS. Like IBS, GAD is typically a chronic relapsing illness. It is characterized by the core symptom of pathological worry and other anxiety symptoms including restlessness, easy fatigue, sleep disturbance, muscle tension, difficulty concentrating and irritability. Both IBS and GAD are reactive to stress^[10–12] and are likely to involve central and/or peripheral serotonergic disturbances.^[13,14] They also bring about anticipatory worries and avoidance behaviour that impair functioning in everyday life.^[8,15] The two illnesses add to health-care cost and poor quality of life.^[16,17]

To our knowledge, no previous research has studied, using standardized diagnostic criteria, the relationship between IBS and GAD in a community-based sample. Therefore, we set out to examine the prevalence, comorbidity and risk correlates of IBS and GAD in a general population.

Table 1. Survey questions pertaining to the DSM-IV criteria of Generalized Anxiety Disorder
DSM-IV criteria	Questions in the telephone survey	Required responses for diagnosis
A. Excessive anxiety and worry, occurring more days than not for at least 6 months, about a number of events or activities (e.g. work or school performance)	A1. Do you think that you are prone to anxiety or worries?	At least one response to A1-A3 has to be 'Yes'
	A2. Was there a period in the past 12 months that you were habitually worried?
	A3. In the past 12 months, had you frequently worried about a number of events or activities (e.g. work or school performance)?
	A4. Did your worries or anxiety last more than 6 months?	'Yes'
	A5. During the period when you were worried or anxious, did you experience worries or anxiety for most of the time?	'Yes'
B. The person finds it hard to control the worry	B1. During the period when you were worried or anxious, how often were you able to control your worry?	'Occasionally' or 'Very difficult' or 'Unable to control'
C. The anxiety and worry are associated with 3 (or more) of the following 6 symptoms (with at least some symptoms present for more days than not for the past 6 months) Restlessness or feeling keyed up or on edge Being easily fatigued Irritability Muscle tension Difficulty falling/staying asleep, or restless unsatisfying sleep Difficulty concentrating or the mind going blank	C1. Did you frequently experience the following symptoms when you were worried or anxious: Restlessness Being easily fatigued Irritability Muscle tension Difficulty falling or staying asleep, or restless unsatisfying sleep Difficulty concentrating or the mind going blank	At least 3 of the 6 symptoms have to be met
D. Clinically significant distress or impairment in social, occupational/other important areas of functioning	D1. Did the above experiences cause you significant distress? AND/OR	'Very distressed' or 'Quite distressed' AND/OR
	D2. Did the above experiences significantly impair your daily life, (e.g. study/work, social & family life?)	'Very impaired' or 'Quite impaired'

Table 1. Survey questions pertaining to the DSM-IV criteria of Generalized Anxiety Disorder

DSM-IV criteria

Questions in the telephone survey

Required responses for diagnosis

A. Excessive anxiety and worry, occurring more days than not for at least 6 months, about a number of events or activities (e.g. work or school performance)

A1. Do you think that you are prone to anxiety or worries?

At least one response to A1-A3 has to be 'Yes'

A2. Was there a period in the past 12 months that you were habitually worried?

A3. In the past 12 months, had you frequently worried about a number of events or activities (e.g. work or school performance)?

A4. Did your worries or anxiety last more than 6 months?

'Yes'

A5. During the period when you were worried or anxious, did you experience worries or anxiety for most of the time?

'Yes'

B. The person finds it hard to control the worry

B1. During the period when you were worried or anxious, how often were you able to control your worry?

'Occasionally' or 'Very difficult' or 'Unable to control'

C. The anxiety and worry are associated with 3 (or more) of the following 6 symptoms (with at least some symptoms present for more days than not for the past 6 months)

Restlessness or feeling keyed up or on edge
Being easily fatigued
Irritability
Muscle tension
Difficulty falling/staying asleep, or restless unsatisfying sleep
Difficulty concentrating or the mind going blank

C1. Did you frequently experience the following symptoms when you were worried or anxious:

Restlessness
Being easily fatigued
Irritability
Muscle tension
Difficulty falling or staying asleep, or restless unsatisfying sleep
Difficulty concentrating or the mind going blank

At least 3 of the 6 symptoms have to be met

D. Clinically significant distress or impairment in social, occupational/other important areas of functioning

D1. Did the above experiences cause you significant distress? AND/OR

'Very distressed' or 'Quite distressed' AND/OR

D2. Did the above experiences significantly impair your daily life, (e.g. study/work, social & family life?)

'Very impaired' or 'Quite impaired'

Table 2. Sociodemographic characteristics of respondents
	Total sample (n = 2005)	IBS (n = 109)	GAD among IBS (n = 18)
n	% (Census % 2006)*	%	Crude OR	P	%	Crude OR	P
Gender
Female	1056	52.6 (52.8)	6.2	1		21.9	1	0.09
Male	949	47.4 (47.2)	4.6	0.754	0.158	9.1	0.374
Age
15–24	351	17.5 (17.9)	3.4	0.426	0.022	8.3	0.404	0.486
25–34	404	20.2 (20.7)	4.5	0.559	0.08	5.6	0.353	0.373
35–44	508	25.4 (24.6)	7.1	0.927	0.791	22.2	1.507	0.575
45–54	467	23.3 (23.5)	4.7	0.604	0.109	22.7	1.8	0.453
55–65	274	13.7 (13.2)	7.6	1	–	14.3	1	–
Education level
Primary or below	257	12.9 (17.1)	7	1.056	0.856	23.5	4.847	0.076
Secondary	973	48.9 (50.5)	4.3	0.652	0.067	28.6	5.918	0.021
Pre-college	203	10.2 (15)	6.4	0.955	0.892	0	–	0.999
College or above	558	28.0 (17.3)	6.5	1	–	5.6	1	–
Work status
Employed	1234	61.5	5.6	1.274	0.453	13	0.23	0.032
Unemployed	149	7.4	8.7	2.065	0.08	23.1	0.497	0.42
Retired	115	5.7	7	1.56	0.349	12.5	0.122	0.15
Student	242	12.1	2.9	0.605	0.307	0	–	0.999
Take care of the family	264	13.2	4.5	1	–	41.7	1	–
Marital status
Single	734	36.6 (37.2)	4.6	0.579	0.332	6.1	0.398	0.554
Married/living together	1222	61.0 (57.1)	5.8	0.743	0.589	21.1	1.426	0.804
Previously married	49	2.4 (5.6)	8.2	1	–	25	1	–
Income level
HKD30000 or below†	1449	72.3	5.5	0.841	0.622	21.5	2.949	0.364
HKD30000 –$60000	403	20.1	5	0.766	0.508	5	0.45	0.625
HKD60000 or above	152	7.6	6.5	1	–	10	1	–

Table 2. Sociodemographic characteristics of respondents

Total sample (n = 2005)

IBS (n = 109)

GAD among IBS (n = 18)

% (Census % 2006)*

Crude OR

Gender

Female

1056

52.6 (52.8)

6.2

21.9

0.09

Male

949

47.4 (47.2)

4.6

0.754

0.158

9.1

0.374

Age

15–24

351

17.5 (17.9)

3.4

0.426

0.022

8.3

0.404

0.486

25–34

404

20.2 (20.7)

4.5

0.559

0.08

5.6

0.353

0.373

35–44

508

25.4 (24.6)

7.1

0.927

0.791

22.2

1.507

0.575

45–54

467

23.3 (23.5)

4.7

0.604

0.109

22.7

1.8

0.453

55–65

274

13.7 (13.2)

7.6

–

14.3

–

Education level

Primary or below

257

12.9 (17.1)

1.056

0.856

23.5

4.847

0.076

Secondary

973

48.9 (50.5)

4.3

0.652

0.067

28.6

5.918

0.021

Pre-college

203

10.2 (15)

6.4

0.955

0.892

–

0.999

College or above

558

28.0 (17.3)

6.5

–

5.6

–

Work status

Employed

1234

61.5

5.6

1.274

0.453

0.23

0.032

Unemployed

149

7.4

8.7

2.065

0.08

23.1

0.497

0.42

Retired

115

5.7

1.56

0.349

12.5

0.122

0.15

Student

242

12.1

2.9

0.605

0.307

–

0.999

Take care of the family

264

13.2

4.5

–

41.7

–

Marital status

Single

734

36.6 (37.2)

4.6

0.579

0.332

6.1

0.398

0.554

Married/living together

1222

61.0 (57.1)

5.8

0.743

0.589

21.1

1.426

0.804

Previously married

2.4 (5.6)

8.2

–

Income level

HKD30000 or below†

1449

72.3

5.5

0.841

0.622

21.5

2.949

0.364

HKD30000 –$60000

403

20.1

0.766

0.508

0.45

0.625

HKD60000 or above

152

7.6

6.5

–

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