Hi, Thanks for writing in. It is common to have diarrhea during panic attacks however anemia is not common and probably it is to do with his food habit. Stress causes panic attacks in many young people and this can trigger the sympathetic and parasympathetic nervous system and diarrhea occurs. If he is taking iron supplements then there is no problem and he should eat iron containing foods like fruits and vegetables. The diarrhea is due to anxiety and with behavior therapy he can control it. If the anxiety is high then consulting a psychiatrist is suggested. With medications and cognitive behavior therapy many patients show improvement. Please do not worry.