I mean depression could do that to a person too depending how bad it is
Isn't it because his brother can't get guiding beside from YG? But because they are brothers YG cannot give intense guiding more than a hug and it's not enough for the brother, cmiiw
It's cause they were poor so they often didn't have nutritious meals and then he couldn't receive proper guiding. His brother tried his best with guiding him through hugs and holding hands but sometimes he needed extensive guiding and you can only get that through sexual contact. So that was off the table. Plus stress & depression, lack of sleep. Everything combined was wearing down his body. But the main issue was guiding.
Couldn't afford proper guiding, since that means sex... and he wasn't gonna fuck his lil bro.
But general starving probably didn't help.
But damn why his brother looks like an addict? Is his brother have sick, I thought it's just a depression in early chapters and