Stress can aggrevate GERD but it cant cause the condition.
I'm happy to be corrected if i am mistaken, but GERD cause is from a weak LES valve therefore not enough pressure/control to keep contents in the stomach properly.
The stomach creates positive pressure and the chest creates negative pressure (or vice versa). These equate and cancel eachother out keeping everything in place inside the stomach. When condition exist like a weak LES, this no longer stands hence GERD. Other factors like hiatal hernia attribute to the condition also but again this does not directly cause GERD.
This is a summary of what was explained to me in great detail by my consultant who did my NF and hiatal hernia repair.