from what I learned at my nutrition school when the body is under stress,  it's called in anthropological terms, the 'fight or flight' syndrome.  whereby your body thinks it is under a threat of some kind and reacts accordingly.  even if in modern times most of what we perceive as a threat is psychological whereas in primitive times we were being chased by tigers!! each one is a different stressor but your body only knows that it feels threatened and creates the same response, tiger or being late to work.  real or otherwise.   \nyour body then produces stress, it copes with whatever this stress is by shutting down diffferent systems so that it can survive most efficiently.  Either by running away or fighting the tiger(metaphorically or literally).  digestion is absolutely one of them.  when in a stressful situation your bowels are the last thing you need to think about if per say, primatively speaking, you are being chased by a tiger.  some people evacuate immediately: diarrhea or hold it in until they are safe: constipation.   if they are under constant stress, then the body perceives this as a signal to continue coping as it has been which could cause constant constipation and/or diarrhea or other problems such as hormonal imbalances(because when you are super-stressed for example having a baby is the last thing your body can handle), weight gain or loss etc..  \nSuggestions:\n(I have a theory, see if it fits).  I have noticed that people who are prone to consipation tend to be holder-oners.  Those who have a hard time lettting go. Whereas people who are prone to diarrhea tend to be letter-goers.  Those who have a harder time facing things and move fast to avoid things.  Both by personal experience and talking with people who suffer from both of these issues.  Take a look at your life, your material belongings and see which one fits...if not.  Then my theory is off)\nYou can look into is meditation or tai chi for calm stress reduction or even martial arts to get some anger and aggression out...stress reduction at it's funnest and finest!!! \nCalcium/magnesium is good for nerve balancing and muscle contraction and relaxation.  make sure you have the right ratio.  especially magnesium( most of America are deficient).\n\ngood luck, \nhang in there...\nhope this helps!
does stress cause having a bowel movement to be harder?