Does boxing cause brain damage? This article says: "Almost certainly": https://www.livescience.com/1519-boxing-brain-damage.html
Does boxing cause brain damage? This article says: "Almost certainly": https://www.livescience.com/1519-boxing-brain-damage.html
There's also forms of karate that allow full contact.
But I look at Thai Boxing matches with flying knees, elbows, etc and that recent video where a fighter footswept someone and then kneed them in the head on the way down and I think "Fuck that."
One area that is different to a lot of other sports is that fights aren't stopped for bleeding often as it is very common for thai style elbows to open gashes on the face. A lot of experienced fighters will have scarring around the eyes from getting cut with elbows.
That said in the west fights are split into 3 classes (4 if you include novice fights) C which has no elbows or knees to the head, B which has no elbows to the head and A which uses All legal thai techniques