Through the science of functional medicine, a new way of thinking about how to solve this (and every other!) complex health problem, you can fix this problem quickly by simple changes in diet and a few other simple strategies.
How long does it really take to change a habit? I definitely don't think the 21 days my friend referenced is enough, and if my experience is any guide, the 45 days isn't long enough to really change a habit, either.
Although everyone is stressed out to some degree, and everyone has occasions where they feel their negative emotions in their gut, those with irritable bowel syndrome (IBS) seem to have an enhanced sensitivity to the feedback that the gut sends to the brain.
The golden rule: an underlying medical illness or medication side effect has to be ruled out before ever deciding that someone's symptoms are caused by mental disorder. And the underlying medical illness may take time to declare itself.