I have no problem believing the story, but I wouldn't necessarily put it beyond the placebo effect. While panic attacks can have very real physiological symptom

I have no problem believing the story, but I wouldn't necessarily put it beyond the placebo effect. While panic attacks can have very real physiological symptoms, their origin is almost exclusively psychological. So if you truly believe that something prevents panic attacks, there's a good chance it will actually do so - no matter how realistic it is from a purely objective, physiological point if view.