Crohn's disease is an inflammatory bowel disease (IBD) that causes inflammation or ulceration of the digestive tract. It can affect any part of your digestive tract, but it is most common in the last part of the small intestine (ileum) and the large intestine (colon).

Crohn's disease affects the deepest layers of the lining of the digestive tract, causing deep sores called ulcers.

Crohn's disease and ulcerative colitis (which affects the colon and rectum) are the most common types of inflammatory bowel disease, with ulcerative colitis being more common.

What causes Crohn's disease?

The cause of Crohn's disease is not known. It sometimes runs in families, suggesting a genetic link. The immune system may overreact to normal intestinal bacteria and cause inflammation. Disease-causing bacteria and viruses also may play a role in triggering the condition, and smoking increases the risk of Crohn's disease.

Increasingly, researchers think environmental factors play a role in causing Crohn's disease.

What are the symptoms?

The main symptoms of Crohn's disease are abdominal pain, rectal bleeding, and diarrhea. Constipation, fever, and loss of appetite may also occur.

Crohn's disease also may cause:

• Sores in the mouth.
• Nutritional deficiencies, such as lowered levels of vitamin B12, folic acid, iron, and fat-soluble vitamins, because the intestines may not be able to absorb nutrients from food.
• Bowel obstruction.
• Anal tears (fissures) or openings (fistulas), abscesses, or skin tags that may resemble hemorrhoids.
• Joint aches and fatigue.

Sometimes complications develop elsewhere in the body (systemic), including the eyes, liver, blood, and bones. These systemic symptoms suggest immune system involvement.

Ulcerative colitis is a type of inflammatory bowel disease (IBD) that causes inflammation and sores (ulcers) in the inner lining of the colon and rectum. It causes diarrhea, abdominal pain, and rectal bleeding.

Ulcerative colitis is a chronic condition that may flare up many times during life. A person may have long periods without symptoms or may have only mild symptoms, while other people have symptoms that are more persistent and severe.

Ulcerative colitis is treated with medications or with surgery to remove the diseased colon. Treatment depends on the severity of the attack and the person's age. Children and older people may have specific problems that require special care.

Description and benefits of psychological treatment

Crohn's disease can affect every aspect of your life. It may make you feel isolated or depressed. But you can take steps to improve your outlook and coping skills. You may want to seek professional counseling and social support from family, friends, or clergy. Research has shown that strong social support can reduce stress and disease activity.  (Sewitch MJ, et al. (2001). Psychological distress, social support, and disease activity in patients with inflammatory bowel disease.

American Journal of Gastroenterology, 96(5): 1470–1479.)