To Name :
To Email :
From Name :
From Email :
Comments :

Primary Care Update

Irritable bowel syndrome and psychiatric illness: Three clinical challenges

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

Vol. 2, No. 6 / June 2003

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







Additive sedation

Additive dizziness, sedation, dry mouth,

Contraindicated–hyperpyrexia and severe neurologic effects

Contraindicated–hyperpyrexia, seizures, and death


Additive sedation

Additive sedation


Increased tricyclic levels with concurrent use


Additive sedation, dry mouth

Additive sedation

Additive sedation, dry mouth, increased tricyclic levels



Additive sedation

Additive sedation

Increased levels of anticonvulsants

Additive sedation, dry mouth, constipation


Additive sedation


Additive sedation and dry mouth

Additive sedation


Additive sedation, dizziness

Additive sedation

Additive sedation, dizziness, nausea

Additive sedation, dry mouth, constipation, increased tricyclic level

Traditional antipsychotics

Additive sedation, CNS effects

Additive sedation, CNS effects

Additive sedation, dizziness

Additive sedation and anticholinergic effects; increased tricyclic level

Atypical antipsychotics

Additive sedation, CNS effects

Contraindicated–respiratory and cardiovascular collapse

Elevated antipsychotic levels

Levels of both drugs increased



Additive sedation

Increased blood levels of aripiprazole

Increased 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.


‘Alarm symptoms’ requiring medical workup in patients with abdominal pain

  • Hematochezia
  • Weight loss < 10 pounds
  • Family history of colon cancer
  • Recurrent fever
  • Anemia
  • Chronic severe diarrhea

Source: American College of Gastroenterology Functional Gastrointestinal Disorders Task Force. Am J Gastroenterol. 2002;97:S1-S5.

Other than fiber supplements, most traditional IBS medications are sedating and are associated with anticholinergic side effects. In Ms. H’s case, extreme caution is necessary before prescribing an antidepressant or antipsychotic because of dicyclomine’s additive sedating effects.

Case 2 concluded: After a thorough initial patient interview, the psychiatrist elects to treat Ms. H’s major depression with an antidepressant but delays the use of an antipsychotic to avoid additive sedation.

After talking with Ms. H’s family physician, the psychiatrist stops her dicyclomine and starts sertraline, 100 mg/d. She tolerates the sertraline well and the dosage is titrated across 1 month to 200 mg/d.

Four weeks later, Ms. H’s Beck Depression Inventory score has improved from 26 at baseline to 5, but her paranoid thoughts and frequent diarrhea persist. The psychiatrist adds low-dose olanzapine (5 mg at bedtime) to minimize extrapyramidal side effects. One month later, her depression and paranoia have resolved.

Ms. H’s gastroenterologist instructs her to begin taking alosetron, 1 mg bid, for her continued frequent diarrhea. Adding this agent to her sertraline/olanzapine regimen can lead to additive constipation and abdominal pain, so the psychiatrist monitors her psychiatric medications. One month later, she reports that her affect is much improved and her diarrhea is “gone.”


Mr. J, age 52, has had depression for 1 year. His depressive symptoms have improved significantly on fluoxetine, 20 mg/d; he once again enjoys life and has a more positive outlook.

The patient was in reasonably good health until about 1 month ago, when he began to experience abdominal pain. He has lost 14 lbs over the past month. He is not taking other medications.

The challenge: Find the cause of Mr. J’s persistent abdominal pain without undermining depression therapy.

Discussion: Although Mr. J’s symptoms might be side effects of fluoxetine, his abdominal pain and weight loss >10 lbs within 1 month are cause for concern. The American College of Gastroenterology has identified six alarm symptoms that could point to a serious medical problem in patients with severe abdominal pain (Box).7

Patients who exhibit any of these symptoms should be referred for endoscopic and stool studies. Colon cancer screening should be considered for all patients age 50 and older.

Patients with IBS usually present first to their primary care physicians with abdominal pain and altered bowel habits. These symptoms can occur in many gastrointestinal and systemic illnesses (Table 2).8

Table 2

Diagnosing irritable bowel syndrome: What to rule out

Differential diagnosis


Inflammatory bowel disease

Crohn’s disease, ulcerative colitis

Medication effects

Laxatives, constipating agents


Parasitic, bacterial, viral, opportunistic

Malabsorption syndromes

Celiac disease, pancreatic insufficiency

Endocrine disorders

Hypothyroidism, hyperthyroidism, diabetes, Addison’s disease

Endocrine tumors (extremely uncommon)

Gastrinoma, carcinoid

Colorectal carcinoma

Adenocarcinoma, villous adenoma

Intestinal pseudo-obstruction

Diabetes, scleroderma

Lactose intolerance


Psychiatric disorders

Depression, anxiety, somatization disorders

Source: Dalton CB, Drossman D. Am Fam Physician. 1997;55(3):875-80.

Case 3 concluded: The psychiatrist and primary care physician consult a gastroenterologist, who performs a colonoscopy and identifies a resectable Duke’s Class B adenocarcinoma in the transverse colon. A partial colectomy is performed.

Three years later, Mr. J is cancer-free and his depression is stable. The psychiatrist advises him to keep taking fluoxetine, 20 mg/d, because the stress of his cancer therapy increases the risk of depression recurrence.

Related resources

Drug brand names

  • Alosetron • Lotronex
  • Aripiprazole • Abilify
  • Buspirone • BuSpar
  • Desipramine • Norpramin
  • Dicyclomine • Bentyl
  • Fluoxetine • Prozac
  • Olanzapine • Zyprexa
  • Sertraline • Zoloft


The author reports no financial relationship with any company whose products are mentioned in this article or with manufacturers of competing products.


1. Locke GR, 3rd. The epidemiology of functional gastrointestinal disorders in North America. Gastroenterol Clin North Am. 1996;25:1-19.

2. Goldberg J, Davidson P. A biopsychosocial understanding of the irritable bowel syndrome: a review. Can J Psychiatry. 1997;42:835-40.

3. Aaron LA, Burke MM, Buchwald D. Overlapping conditions among chronic fatigue syndrome, fibromyalgia, and temporomandibular disorder. Arch Intern Med. 2000;160:221-7.

4. Smith RP. Lower gastrointestinal disease in women. Obstet Gynecol Clin North Am. 2001;28:351-62.

5. Olden KW, Drossman DA. Psychologic and psychiatric aspects of gastrointestinal disease. Med Clin North Am. 2000;84:1313-276.

6. Mobile PDR Release Version 32. Database Version 437. An abbreviated, up-to-date version of the PDR onto computing devices. Thomson Healthcare, Ortho-Biotech Oncology, 2003.

7. American College of Gastroenterology Functional Gastrointestinal Disorders Task Force. Evidence-based position statement on the management of irritable bowel syndrome in North America. Am J Gastroenterol. 2002;97:S1-S5.

8. Dalton CB, Drossman D. Diagnosis and treatment of irritable bowel syndrome. Am Fam Physician. 1997;55(3):875-80.

Did you miss this content?
Botulinum toxin for depression? An idea that’s raising some eyebrows