At the time, I had undiagnosed OCD. And, it turns out, the medicine which I was being given against my will for an ADHD diagnosis I received at age 5, was causing me to experience dry mouth, which made me instinctually suck on the buttons and corners of my shirt. Mystery solved. But two therapists and years of punishment didn't figure that out. I did, in my adulthood.
I had the same experience with uncontrollable, hour-long bouts of laughter which would end in vomiting and extreme stomach pain. Punished for them, told I was just trying to get attention. Turns out that was an expression of OCD. And dozens of other things not worth mentioning. The older I got, the more I came to appreciate the level of misunderstandings about my issues which led to even more violence inflicted upon me.
So that is a possible avenue of explanation for why RSD and ADHD seem to be correlated. After speaking with some friends who have borderline disorder (I don't have this, but I do have bipolar disorder type II) it seems to be something they have experienced as well. And a great deal of BPD cases involve trauma.
There is little doubt that something chemical is taking place given that specific gene mutations seem to cause these disorders, or at least predispositions to them. I'm sure that there is a correlation between RSD and the dopamine reuptake issues which characterize ADHD. But the feedback systems in nature vs nurture mean that these disorders can cause problems which themselves exacerbate the disorders or cause new symptoms to present.
That would definitely make a lot of sense.
You are never taught how to properly tend to the emotions of both yourself and others, so unless you pair with an emotionally well-adjusted partner, you will lack the emotional knowledge required to teach your children better. And what's worse, your brain will relapse into the habits it does have experience, which may often be negative.
And boom, we have the wheel and the multigenerational cycle of abuse.
If someone was neglected or attacked by a caregiver when they approached them for help, especially if it was infrequent, and repeatedly told they weren’t allowed to feel bad about it/it wasn’t happening/if it was happening it was all their fault, and suffered significant distress because of it - how else would it present?
Especially if it was at an age where they couldn’t process or verbalize what was going on, and the parent was one they couldn’t reject themselves (because they needed them or they’d be orphans or whatever).
If RSD is really due to emotional neglect/rejection based Complex PTSD underlying the whole thing. It would make a lot of sense.