Evidence-Based Reviews

Irritable bowel syndrome and psychiatric illness: Three clinical challenges

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Target specific symptoms, consider possible drug-drug interactions, and watch for underlying life-threatening complications.



Psychiatrists often treat patients with irritable bowel syndrome (IBS) and an accompanying mental illness. Knowledge of available treatments and communication with the referring doctor are crucial to treating both the IBS symptoms and the comorbidity.

This article presents three cases that illustrate the challenges of identifying target symptoms, avoiding drug-drug interactions, ruling out serious underlying medical problems, and formulating treatment.


Approximately 12% of the United States population reports IBS symptoms (abdominal pain, bloating, altered bowel habits).1 These symptoms begin before age 35 in most patients and during childhood in some. Onset after age 65 is rare.

IBS is common among patients with alcohol abuse disorder (32%),2 chronic fatigue syndrome (92%), fibromyalgia (77%), or temporomandibular joint syndrome (64%).3 Seventy percent of patients with IBS are women.4 Chronic pelvic pain, dyspareunia, dysmenorrhea, or a history of abdominal surgeries are risk factors for IBS in women.


Although mental illness often coexists with IBS, no cause-effect relationship has been shown.5

IBS is often preceded by stressful life events, such as family death or divorce,3 and some believe IBS is a precursor to numerous psychiatric disorders. Generalized anxiety disorder, major depression, panic disorder, social phobia, somatization disorder, or dysthymia have been diagnosed in most IBS patients.2


Ms. R, age 55, has had IBS for 10 years. She has occasional diarrhea and abdominal cramps relieved by bowel movements. She is taking a bulking agent but still sometimes suffers abdominal pain.

She is referred to a psychiatrist after complaining of fatigue, loss of interest in hobbies, and crying spells for 2 months. She denies suicidal ideations. Her referring physician reports that she is taking conjugated estrogens to manage menopause symptoms. She denies any recent stressful life events. Thyroid function, glucose, and CBC are normal.

The challenge: Deciding which to treat first—the IBS symptoms or the depression—and how.

Discussion: The predominant symptom (in Ms. R’s case, abdominal pain) can help determine choice of medication. Bulk-forming agents, antispasmodics, barbiturates, benzodiazepines, and serotonin reuptake inhibitors have historically been used to treat IBS,6 but scant evidence supports their use.

Obtaining a thorough prescription history from the primary care physician, OB/GYN, and other treatment team members is critical before formulating a treatment plan. Ms. R’s estrogen use will not affect the choice of psychotropic or IBS medication because there are no significant interactions between estrogen and these classes of drugs.

Ms. R’s abdominal pain and depression can be treated simultaneously. Randomized, controlled trials have demonstrated that tricyclic antidepressants reduce abdominal pain and that behavioral therapy (relaxation therapy, hypnotherapy, and cognitive-behavioral therapy) may relieve individual IBS symptoms.7

Case 1 concluded: After reviewing Ms. R’s medications, the psychiatrist starts:

  • desipramine, 50 mg at bedtime, to minimize anticholinergic side effects
  • and short-term psychotherapy, which helped her identify support mechanisms and ways to better balance her life stresses.

After 6 weeks, her Beck Depression Inventory score improved from 30 at baseline to 8. She reports her abdominal pain is “the best it has been in 10 years.” Six months after diagnosis, she continues to take desipramine and is doing well.


Ms. H, age 32, is referred to a psychiatrist for treatment of depression with paranoid features.

Four years ago, a gastroenterologist diagnosed her as having IBS. She experiences frequent diarrhea and lower abdominal cramping. For 2 years she has been taking the antimuscarinic dicyclomine, 10 mg tid, which has provided some relief from her cramps. An estimated 20 diarrhea attacks per day leaves her housebound much of the time, however.

She reports fatigue, loss of interest in hobbies across 2 months, and paranoid thinking. She denies hallucinations or delusions but believes that her teenage children are discussing her “sickness” and plotting to “drive her crazy.” She is not suicidal.

The challenge: Treating Ms. H’s depression and paranoia while avoiding drug-drug interactions.

Discussion: Adverse drug-drug interactions can occur when prescribing psychotropics to patients with IBS (Table 1). Additive constipation, diarrhea, abdominal pain, and sedation are common interactions between psychotropics and the 5-HT3 antagonists and 5HT4 agonists commonly prescribed for IBS.

Table 1

Interactions between psychotropics and agents prescribed for IBS

MAOIsAdditive sedationAdditive dizziness, sedation, dry mouth,Contraindicated–hyperpyrexia and severe neurologic effectsContraindicated–hyperpyrexia, seizures, and death
SSRIsAdditive sedationAdditive sedation—-Increased tricyclic levels with concurrent use
TricyclicsAdditive sedation, dry mouthAdditive sedationAdditive sedation, dry mouth, increased tricyclic levels—-
AnticonvulsantsAdditive sedationAdditive sedationIncreased levels of anticonvulsantsAdditive sedation, dry mouth, constipation
BenzodiazepinesAdditive sedation—-Additive sedation and dry mouthAdditive sedation
BuspironeAdditive sedation, dizzinessAdditive sedationAdditive sedation, dizziness, nauseaAdditive sedation, dry mouth, constipation, increased tricyclic level
Traditional antipsychoticsAdditive sedation, CNS effectsAdditive sedation, CNS effectsAdditive sedation, dizzinessAdditive sedation and anticholinergic effects; increased tricyclic level
Atypical antipsychoticsAdditive sedation, CNS effectsContraindicated–respiratory and cardiovascular collapseElevated antipsychotic levelsLevels of both drugs increased
AripiprazoleSomnolence,constipationAdditive sedationIncreased blood levels of aripiprazoleIncreased sedation and anticholinergic effects
Psychotropics and 5-HT3 antagonists taken concomitantly typically lead to additive constipation and abdominal pain.
Psychotropics and 5-HT4 agonists taken concomitantly typically lead to additive diarrhea and/or abdominal pain.
Source: Physician’s Desk Reference. Mobile PDR release version 32. Database version 437. Montvale, NJ: Thomson Healthcare 2003.


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