Can stress cause atrial fibrillation?

Yes: Yes it is possible, especially if the heart is damaged , or enlarged.

Generally, not: If there is no underlying cardiac problems that may predispose one to atrial fibrillation, it would be unusual for stress to be actual cause; however stress can be the underlying to so many maladies, that one never says never. If one develops atrial fib, must look for underlying heart disease, and--even it none is found-be treated for it by cardiologist specializing in cardiac rhythm disorders.