Genetics play a significant role in ulcerative colitis risk. Having a first-degree relative (parent, sibling, or child) with the condition increases your risk by 2-4 times. Certain genetic mutations, particularly those affecting the immune system, have been associated with higher risk. However, many people with these genetic factors never develop the disease, indicating that other factors are also important.

Several environmental factors may influence ulcerative colitis risk. Interestingly, smoking appears to be protective against ulcerative colitis, although it's harmful in many other ways. A diet high in processed foods and low in fiber may increase risk. Stress doesn't cause ulcerative colitis, but it may trigger flares in those who have the condition.

Ulcerative colitis can develop at any age, but it's most commonly diagnosed in people in their 30s. There's also a smaller peak in diagnosis around age 60. The condition is more common in developed countries, particularly in urban areas, suggesting that factors related to industrialization may play a role.

While these factors can increase risk, many people with risk factors never develop ulcerative colitis, and the condition can occur in those without obvious risk factors.