I think if you look into the literature (there are some books listed in the library here on the site), you’ll find that high sensitivity is definitely genetic. And then the nurture piece follows from that. In her work, Dr. Aaron talks about how highly sensitive children who grow up in difficult environments end up having a hard time in life, and how highly sensitive children who were well supported tend to be more well adjusted than the average person.
Having gone through a very difficult time myself growing up, it was a big moment for me when I realized that my high sensitivity was underneath all the damage. Meaning, though it was not supported when I was growing up, it’s still there for me to claim and nurture now.