[Boaty McBoatface]

This has been a question that has been nagging at me for awhile, but I never found the right place to ask. I it possible that a concussion could keep a personality disorder from forming? I know this is a weird question, so let me explain.

I won't recap my situation too much since I recently made a big long post. However, when I was 5, I was hit by a car causing a grade 3 concussion (I was unconscious for at least 15 minutes.) Ever since then, my family said I had a drastic personality change. I never paid too much attention to it, because how could you tell the personality of a 5 year old?

Before I go on, I have to thrown in the disclaimer everything past this point must be taken with a grain of salt as I am in no way a trained psychologist, neurologist, etc and I realize I cannot properly diagnose anyone.

With that out of the way, I am EXTREMELY different from the rest of my family, personality wise. My mom, dad and sisters are extremely extroverted, love meeting new people, and based on several conversations I've had with them, have never been introspective or meta-cognitive. I'm extremely introverted and shy, dislike meeting new people, and I'm buried inside my own head to a rather unhealthy degree. I could never understand why, when going to a restaurant, my family would make conversation with the hostess, the waiter, the family next to us, etc. They could never understand why, after school, I'd go straight to my room and not talk to anyone for a few hours.

Here's the tricky part. Multiple members of my immediate family going through three generations have displayed traits of someone suffering from a cluster B personality disorder. My grandma seemed to treat people, including her kids, as possessions and never let them make any decisions for themselves. To disagree with her on anything meant retribution, usually by not talking to them for years. At least one of my sisters seems to conform with Narcissistic Personality Disorder. She views any form of disagreement as traitorous and will go to war with people who she feels has wronged her in some way. She has surrounded herself only with people who compliment her constantly, and her kids know the best way to get something from her is to suck up to her. Most of my family members are also very paranoid. Any problem they encounter is interpreted as a personal attack. (If we go to a restaurant and another party gets seated before us, the host obviously did that to spite us.)

I could go on and on, but I'll just get to the point. Is it theoretically possible that a TBI severe enough to cause a personality change prevent these types of personality disorders* from forming? Are there any twin studies that show dramatic differences in personalities due to one having a TBI? The fact that I'm so different in personality than anyone else in my family has been a giant mystery to me for decades. I can't help but suspect that I'd be a lot more like them (for better or for worst) if I hadn't have been hit by a car.

*Again, they have not been diagnosed and I am not trained.