One of my most intense interests regarding psychedelics and mental health now is related to a brain system known as "the default mode network". It regulates many things developmentally, has been closely linked to the development of what we often describe as a sense of self, consciousness, and many "disorders" (including the so-called personality and dissociative disorders) where these things do not develop normally or get out of control, due to a great variety of factors, both inborn and environmental. Possible dysregulation in this network is also known to lead to various mood and behavioral problems.

The New Science of Psychedelics: A Tool for Changing Our Minds
Psychedelics and the Default Mode Network – Psychedelics Today

I have never been diagnosed with any personality disorder and never never even doubted my integrity in that regard... the "well-integrated" nature of my psyche has been commented on by my ex-Ts as well in my early 40s, even the "bad" T who had little clue about these things and was very self-absorbed and narcissistic. I sometimes wonder now if my mostly careful, methodical use of psychedelics in my later 20s has contributed to this introspective identity and sense of self? A lot of my most intense, personal, self-exploring journey started back then... and never stopped later, except during some very dark, but always temporary periods later in life. It was only severe substance addiction that halted it (I believe I am genetically predisposed as there were severe cases in both lineages of mu family), but was even fairly easy to recover my strong sense of self and interests once the addiction had been resolved for a few months. Maybe I could achieve these things relatively easily as I had a pretty decent, supportive childhood with good enough parents... I actually often think my early childhood was preventive, as many more serious mental health issues run in my family, for people who have not had similar childhood and care.

There might be an inborn predisposition, but "nurture" might be able to adjust it somewhat, and then it's easier to build upon that with independent explorations? Conversely, if that was not established "from start" it may be much trickier to apply any external intervention... including psychedelics.