I think that ADHD is something someone can be born with. I have had to deal with this challenge all my life, not in myself but in someone else connected to me. My older brother and my husband. What I have seen with both of them is that from an early age they both were very much "in motion" and struggled to sit still and relax and pay attention. Unfortunately, these children are "misunderstood" and are often "punished" instead of having the right kind of help. This creates problems with "self esteem" and these individuals often develop some coping methods that can be very "harmful", not only for themselves but for others who are around them. And "yes" some personality disorders can develop and even can lead to what is called "complex PTSD".

Unfortunately, not all children can be expected to fit into a box where they have the ability to follow a certain structure that is set up in a school environment. And these children have long been punished instead of being recognized and helped properly.
The methods of "punishment" often made these children even worse, I observed that first had growing up with my older brother, it was a horrific thing to witness on a daily basis.
As a result, I am sure my older brother suffers from complex PTSD and so do I.

OE