A hernia forms when an organ or tissue pushes through a weak spot in the muscle or connective tissue that normally holds it in place. The basic cause is always the same: internal pressure exceeds the strength of the surrounding wall. But what creates that weakness, and what generates that pressure, varies depending on the type of hernia and the person.
Nearly 147 million people worldwide live with a hernia, and men develop them roughly two and a half times more often than women. Understanding what causes them starts with how your abdominal wall works and what can go wrong.
How the Abdominal Wall Fails
Your abdominal wall is a layered structure of muscle, tendon, and a tough sheet of connective tissue called fascia. Together, these layers hold your organs in place, support your posture, and contain the pressure that builds inside your abdomen whenever you cough, strain, or lift something heavy. A hernia develops when this load-bearing layer loses its structural integrity, either because it was never fully formed, because it weakened over time, or because it was damaged by surgery or injury.
The connective tissue in your abdominal wall relies on constant biological maintenance. Cells called fibroblasts respond to mechanical forces by producing and remodeling collagen, the protein that gives fascia its strength. When that maintenance process breaks down, whether from aging, disease, or disrupted healing, the tissue can no longer handle the forces placed on it. A gap opens, and whatever is behind it starts to push through.
Pressure That Pushes Tissue Out
A weak spot alone isn’t always enough to cause a hernia. It usually takes a force pushing from inside. Any action that raises pressure inside your abdomen can be the trigger. Heavy lifting is the classic example: bearing down against a closed airway (what doctors call a Valsalva maneuver) sharply increases pressure in both the chest and abdomen. That pressure transmits directly to any existing defect in the abdominal wall, widening the gap and forcing tissue through it.
Other everyday activities that raise abdominal pressure include:
- Straining during bowel movements, especially with chronic constipation
- Persistent, forceful coughing from conditions like COPD or chronic bronchitis
- Repeated vomiting
- Strenuous exercise, particularly movements involving heavy loads on the core
None of these activities guarantee a hernia. They matter most when the wall is already compromised. A person with strong, intact fascia can lift heavy weights without issue. Someone with a collagen disorder or a healing surgical wound may develop a hernia from coughing.
Inguinal Hernias: The Most Common Type
Inguinal hernias account for the majority of all hernias and occur in the groin, where a natural passageway called the inguinal canal runs through the abdominal wall. This canal exists because of how the body develops before birth. During fetal development, a tube of tissue called the processus vaginalis pushes through the abdominal wall, creating the inguinal canal. In males, this pathway guides the testes down into the scrotum. Once that job is done, the tube is supposed to close and disappear through programmed cell death.
In about 90% of adults with an indirect inguinal hernia, that closure never fully happened. The processus vaginalis stayed open, leaving a direct path from the abdominal cavity into the inguinal canal. In children, a persistent opening is almost always the cause. The reasons it fails to close aren’t entirely understood, but premature birth, hip dysplasia, Ehlers-Danlos syndrome, and cystic fibrosis are all associated with it.
Direct inguinal hernias, by contrast, develop later in life when the floor of the inguinal canal weakens from aging, strain, or both. These are more common in older men and are the type most closely linked to years of physical stress on the groin area.
Hiatal Hernias: Stomach Through the Diaphragm
Not all hernias involve the abdominal wall. A hiatal hernia happens when part of the stomach slides upward through the opening (hiatus) in the diaphragm where the esophagus passes through. The diaphragm is a dome-shaped muscle separating your chest from your abdomen, and the hiatus is a natural weak point.
The most common causes are age-related weakening of the diaphragm muscle and sustained pressure from below. People over 50 and those who are obese face the highest risk. Repeated coughing, vomiting, straining during bowel movements, and heavy lifting can all contribute. Unlike groin hernias, hiatal hernias affect men and women at similar rates and often produce no visible bulge. Instead, they tend to cause acid reflux and heartburn as the stomach’s position shifts.
Incisional Hernias After Surgery
Any surgery that cuts through the abdominal wall creates a temporary vulnerability. Incisional hernias develop at or near the scar, and they’re surprisingly common: up to 20% of midline abdominal incisions result in an incisional hernia within three years. One large study tracking over 4,400 surgical patients found hernia rates of 3% at one year, 6% at three years, and 8% at five years.
The reason comes down to how wounds heal. In the first days after surgery, the wound is at its weakest. The body is actively breaking down damaged tissue before rebuilding it, and enzymes involved in that cleanup actually reduce the strength of the tissue right at the wound edge where sutures are placed. As patients recover and become more active, loads on the abdominal wall increase. If the wound hasn’t regained enough strength, it can pull apart.
Several factors raise the risk of an incisional hernia. Wound infections are a major one, because infection disrupts the healing process. Higher body weight puts more strain on the closure. Emergency surgeries carry more risk than planned ones, partly because wound closure may be less meticulous under urgent conditions and partly because the tissue is more likely to be inflamed. Prior radiation to the abdomen also weakens the tissue’s ability to heal.
Umbilical Hernias and Pregnancy
The navel is another natural weak point in the abdominal wall, a spot where the umbilical cord once passed through. Umbilical hernias are common in newborns and usually close on their own within a few years. In adults, they’re more likely to develop during pregnancy or in people with obesity.
Pregnancy creates a perfect storm for hernias. As the uterus grows, it progressively raises intra-abdominal pressure while simultaneously stretching and thinning the abdominal wall. The separation of the two sides of the abdominal muscles (diastasis recti) is extremely common during pregnancy and can persist after delivery, leaving a wider area of vulnerability. A pregnancy can cause a new hernia or make a previously unnoticed one suddenly apparent as pressure mounts.
Risk Factors That Weaken Tissue Over Time
Beyond the specific triggers, certain conditions make your connective tissue fundamentally less resilient. Aging is the most universal factor. Collagen quality and quantity decline with age, which is why hernias become more common in older adults even without an obvious triggering event. Smoking accelerates collagen breakdown and impairs wound healing, which is why it’s a recognized risk factor for both primary and incisional hernias.
Connective tissue disorders like Ehlers-Danlos syndrome produce structurally weaker collagen throughout the body, making hernias far more likely and more likely to recur after repair. Obesity plays a double role: it increases intra-abdominal pressure while also impairing wound healing and tissue quality. Chronic malnutrition or conditions that deplete protein stores can similarly undermine the body’s ability to maintain and repair its connective tissue.
Family history matters too. If your parents or siblings have had hernias, your own risk is higher, likely because collagen structure and abdominal wall anatomy are partly inherited. This genetic component helps explain why some people develop hernias despite no obvious strain, while others lift heavy loads for decades without issue.