Does BPD manifest or get worse in the early twenties?
I've read in many places that it typically manifests itself in the early 20s. Although I have seen stories online about persons getting diagnosed with BPD in their teens. I think the general rule is that you're not supposed to diagnose it to someone under 18, in part because so many teens act in erratic ways and it would be difficult to sort out this noise.
From personal experience, the mother of my BPDex said that my BPDex was sweet as can be until her early 20s, and then for some reason (which her mother hadn't identified) the attitude, entitlement, and verbal abuse began.