RSD (Rejection Sensitive Dysphoria), is the most intense side of emotional dysregulation in ADHD. But the opposite side of the spectrum is less known: sometimes, when feelings get too much, some ADHDers get overwhelmed and shut off unwillingly, leading to emotional disengaging.
This is how it goes: two people meet (friendship/relationship). ADHDers often experience bonds in an intense way, connecting strongly with other people. ADHDers can be very empathic. A first the ADHDer will serve as emotional support and advice for person #2
This is done willingly, which makes ADHDers great listeners and advice givers. But if this situation is unbalanced, leading to the ADHDer being always the listener, it can lead to emotional overstimulation. The more intense the relationship, the sooner this can happen.
At this point the ADHDer can disengage from their feelings. This leads to them being missing, more unhealthy hyperfocus, not answering often or as desired, and sometimes even narcissistic and uncaring. In contrast to stage 1 where they were amazing listeners, is a huge contrast.