What I understand today after many years working with trauma survivors is that...
1) having been regularly neglected, ignored, abandoned, discounted, disclaimed, and rejected -- as well as invalidated, confused, betrayed, insulted, criticized, judged, blamed, embarrassed, humiliated, ridiculed, denigrated, derogated, victimized, demonized, persecuted, picked on, dumped on, bullied, gaslighted, scapegoated, and/or otherwise abused -- by others upon whom they depended for survival in early life,...
2) many children develop Learned Helplessness & Victim Identities.
When this occurs, they display a combination of...
. . . a) exaggerated startle response,
. . . c) hypervigilance and
. . . d) interpersonal boundaries that swing back and forth from
. . . . . . 1) extreme porosity (in Walker's "fawn" state") to
. . . . . . 2) extreme density (in fight or flight).
It is my view now that one who grows up with "wounded child syndrome" will have to be "re-raised" or "re-developed" in pretty much the manner described in Erikson's Pathway Out of Kernberg's Hell.
Such "adult children" need to learn emotion & behavior management skills like those in Stress Reduction for Distress Tolerance & Emotion Regulation in order to do sufficient Competence Rebuilding, in my reply on this Reddit thread to both feel okay about themselves and to deal effectively with others.
This is the way I did that, and that I try to teach others to do.