I recently went to a convention about stress induced illnesses and the best answer is none. Stress can cause so many different things in different people, it was an amazing sight to see. Each and everyone of us will treat and deal with stress on different levels so it is hard to pinpoint this as an exact science.
However, what I can provide you is information about aphasia which you can find more information here http://www.medicinenet.com/aphasia/article.htm.
Have you had your brain examined for possible causes? Depression and stress are often related and can be diagnosed and treated usually by pharmaceuticals although exercising has become a better practice.
I hope this information helps at least a little. Concrete information on stress is too up in the air as “stress” itself is hard to measure scientifically.
Keep us posted.