These include loss of a parent, intense conflicts within the family, abusive treatment or neglect, over-controlling or critical parents or siblings, stressful sexual experiences, etc. Research shows correlations between parental adjustment and their children's adjustment, even as married adults. However, childhood traumas are not in the history of every anxious person. We may learn to see the world as uncaring or downright hostile. Contrary to the common view, however, there is evidence that early traumatic experiences are not prophetic, they certainly don't always result in a ruined life.
Humans are pretty tough.
Furthermore, the healing effects of care and love after a trauma are remarkable if we are young. This research doesn't indicate that early traumatic experiences are unimportant, but rather that they could be handled if we knew and cared enough. Certainly, being over-protected and pampered can cause problems too. That is a characteristic of a mature, aware, insightful, wise person. You have to use the understanding to change.