It's likely genetic - i.e. an inherited Anxiety disorder. I have hypermobile Ehlers Danlos Syndrome (hEDS). It disproportionally affects Gifted people and causes a bunch of physical problems that exhibit as mental problems. hEDS is rarely diagnosed and smart people are more able to adapt around the problems and not get diagnosed entirely. It took decades of searching to figure it out myself. This does make me question the Giftedness a bit :) But I am freakishly good a things most normal people are not. So it's swings and roundabouts.