Can stress really make your gut sick?

Stress disrupts the functioning of your gut in several ways at once. The movement of the intestinal wall becomes dysregulated: sometimes the gut works too fast (diarrhoea), sometimes too slowly (constipation). At the same time, sensitivity to pain from the abdominal organs increases, meaning that the same stimulus hits harder in someone under stress than it normally would.

The intestinal wall itself also becomes more vulnerable. Stress makes the gut wall more permeable, allowing particles that would not normally pass through it to do so. This is sometimes called 'leaky gut'. Whether that in itself causes disease has not yet been proven, and there is currently no good evidence that treatments aimed at improving that permeability actually reduce symptoms.

In irritable bowel syndrome (IBS, a condition involving chronic abdominal pain and altered bowel habits), the link with stress is fairly strong. Stress appears to influence both the onset and the worsening of IBS. In chronic inflammatory bowel diseases such as Crohn's disease or ulcerative colitis, the connection with stress is less certain: there is an association, but whether stress actually causes those diseases has not been demonstrated. For stomach ulcers and acid reflux, a probable link with stress also exists.

Stress also has a negative effect on the composition of gut bacteria, but how exactly that works remains largely unknown. Probiotics are being investigated as a possible way to relieve stress-related gut complaints, but the evidence for this is still too thin to base any concrete recommendations on.