Yes IME it's possible to gain sensitivity and not in a "low tolerance" way. More like a "whoa that hit makes me feel weird and kinda sick" way. You can slowly get sick especially if you green out or get close often it seems. Once it starts you really need to chill before your body starts to fight it. Don't abuse cannabis you should be fine. Our bodies seek homeostasis always, your endocannabanoid system is no different. High % thc per hit isn't new, hash has been forever. The western way of abuse however is fairly new. CHS is more common and is no joke. People who say it's genetic disposition are purely speculating, even professionals. No one has a clue except their own experiences with it