My daughter had neither a horrible upbringing nor was she ever mistreated as a child, so I struggle even more to understand why she has this illness.
Science is still struggling to figure out the etiology. I believe the current theory is that it is a combination of genetic predisposition and environmental factors.
If so, that would likely mean that any number of possible percentages could occur ... 1%/99%, 40%/50%, who knows?
In his book about depression - another mental illness where they are trying to figure out the etiology - Perter Kramer talks about resilience
. Someone with a high intrinsic (i.e. genetic) resilience can bounce back from X amount of stress. Someone with low resilience can't. So "is it the stress, or the genetics?" isn't a yes/no question.
Nobody has zero
stress in their upbringing (or adult life). Everyone experiences some
invalidation, disappointment, loss, separation, pain. It's unavoidable. How we react to it - how we even can
react to it - is largely affected by our genetics.