Stress can exacerbate symptoms, it's not necessarily one of the causes of the disease, but more needs to be learned on that too...and from last I read, the jury is still out on weather it's an over-active or under-active immune system so they just chalk it up to a confused/messed up immune system, for some IBDers their immune system may be over active and for others it may be under active at times, again, much more needs to be learned on that too...
from my understanding reading one version of the above article, they will be looking into making a specific probiotic containing F. Prausnitzii to hopefully help us crohnies...that is the crohnies that have a lack of that specific bacterium god only knows if we all do or only the majority or minority of us do....I'm sure they'll have to learn that as well.