I think this is what happened to the relative I lived with. Sustained multiple TBIs from 2002-2006 and refused treatment or therapy. Became paranoid, angry and aggressive with wild mood swings. After a while they became physically abusive. I had to escape the house I grew up in and went No Contact.

I mean, they were a shitty person before, but they became even shittier after. I hope this is studied more.