Introverts Are Especially Vulnerable To Challenges Like Marital Tension, A Parent’s Death, Or Abuse. They’re More Likely Than Their Peers To React To These Events With Depression, Anxiety, And Shyness. Indeed, About A Quarter Of Kagan’s High-reactive Kids Suffer From Some Degree Of The Condition Known As “social Anxiety Disorder,” A Chronic And Disabling Form Of Shyness.