IBD Risk Factors: What Causes Crohn's & Colitis?
Living with inflammatory bowel disease (IBD) can feel overwhelming, especially when you’re searching for answers about what caused it and what you can do to protect your loved ones. While the exact causes of Crohn’s disease and ulcerative colitis remain a complex puzzle, research has revealed a web of genetic, environmental, and lifestyle factors that shape your risk.
As Alan Moss, MD, Chief Scientific Officer at the Crohn’s & Colitis Foundation, emphasized, “We’re increasingly focusing on not just how to treat inflammatory bowel disease, but how to prevent it.”
Understanding IBD Risk Factors
No single factor causes IBD. Instead, it emerges from a combination of genetic susceptibility, immune system responses, and environmental exposures. In people with IBD, the immune system attacks the digestive tract, leading to chronic inflammation. But why does this happen to some people and not others? The answer lies in a mix of inherited risks and life experiences.
The Role of Family History and Genetics
Having a family history of IBD is the strongest known risk factor for developing the disease. If you have a parent, sibling, or child with IBD, your risk is significantly higher than the general population. Studies show that between 5% and 20% of people with IBD have a first-degree relative who also has the disease. The risk is even greater if both parents are affected: research shows that up to 36% of children born to two parents with IBD develop the condition themselves.
Genetic studies have identified hundreds of gene variants associated with IBD, including the well-known NOD2 gene for Crohn’s disease. However, genetics alone does not tell the whole story. As Dr. Moss noted, “If you have a sibling or a parent with IBD, figuring out if you’re at higher risk, and if so, what we could do to prevent you from developing IBD —that’s a really hot topic right now.”
Environmental Risk Factors for IBD: The Gut Microbiome and Early Life Influences
Your gut is home to trillions of bacteria, which play a crucial role in immune health. Disruptions to the gut microbiome—known as dysbiosis—are a hallmark of IBD. Early life factors that can shape your microbiome and risk include:
- Antibiotic use in infancy.
- Being bottle-fed rather than breastfed.
- Growing up in a highly sterile environment.
These exposures may limit the diversity of beneficial bacteria, potentially increasing IBD risk later in life.
Diet, Antibiotic Use, and Urban Living
Where you live and what you eat matter. IBD is more common in developed countries, urban areas, and northern climates. Diets high in processed foods, low in fiber, and rich in animal fats may contribute to risk, while a diet rich in fruits, vegetables, and fiber appears protective. Frequent use of antibiotics—especially early in life—has also been linked to higher IBD risk.
Environmental pollutants, such as microplastics and industrial chemicals, are under increasing scrutiny. Dr. Moss highlighted, “Recently, the Foundation’s focus has turned to conditions that can trigger inflammatory events or relapses, like stress, diet, and environmental pollutants.”
How Lifestyle Choices Can Influence Risk
Certain lifestyle choices can raise or lower your risk of IBD:
- Smoking: Increases the risk for Crohn’s disease.
- NSAIDs: Overuse of nonsteroidal anti-inflammatory drugs (like ibuprofen) can irritate the gut and may trigger or worsen IBD.
- Physical inactivity: Sedentary lifestyles are associated with higher IBD risk, while regular exercise is protective.
Reducing Risk Through Healthy Living
The good news is that lifestyle choices can make a real difference. A major study found that adhering to a nutritious diet, maintaining a healthy weight, staying physically active, and avoiding smoking and unnecessary NSAID use may have protective effects in up to 61% of Crohn’s disease cases and 42% of ulcerative colitis cases. Simple steps like eating more vegetables, moving your body daily, and using medications wisely can support your gut health.
These steps won’t guarantee prevention, but they can lower your risk.
What NOD2 and Other Genetic Research Tell Us About IBD
While genetic research can provide useful information, it cannot predict IBD with certainty. Most people with risk genes never develop the disease, and many people with IBD have no family history.
Research shows that there is a preclinical window of 4 to 7 years before IBD symptoms appear, during which early intervention could help prevent or delay disease onset. Advancing IBD prevention is a core objective in the Crohn’s & Colitis Foundation’s 2025–2028 strategic plan, which specifically aims to drive breakthroughs in the evolving science of IBD prevention and envisions routine screening for those at higher risk as standard practice in primary care.
Dr. Moss noted, “We’re understanding far more about what triggers the disease.” The hope is that, as research advances, genetic and environmental data will help doctors offer more personalized prevention strategies.
If you’re concerned about your risk, don’t hesitate to talk with your healthcare provider or reach out to the Crohn’s & Colitis Foundation for support.
References:
IBD Risk Factors: What Causes Crohn's & Colitis?, July 2025. Available at: https://www.crohnscolitisfoundation.org/blog/ibd-risk-factors-what-causes-crohns-colitis