Thank you for highlighting that emotional dysregulation can have cognitive impacts. But if this were the primary reason for overlap, wouldn't ADHD symptoms be even more pervasive in those with BPD?

I am also not so sure that childhood trauma can help clarify diagnostic issues. I have worked with individuals with BPD for whom certain childhood events were experienced as highly traumatic, yet they seemed comparable to fairly common childhood experiences that don't traumatize others. And again, ADHD itself predisposes to a range of different traumas but those events don't seem to robustly correlate with which children with ADHD go on to develope BPD.