It's mentioned that a character's dad abused alchohol, and there is an option that allow you to obtain a breathalyzer while playing house, but it's never explicitly shown.
Multiple characters, including the player character in certain playthroughs, are given drugs to make them forget an event. One character develops an addiction to said drug.
If you walk into Nugget's cave during recces or ask to go in without Nugget putting nuggets in the cave you will fall down the hole that's suggested to be deep and fall to your death basically. Spoiler: Lily jumps down this hole in Cindy's route and Nugget also goes in this hole shortly after Lily.
Spoiler: Buggs is shown throwing up after you give him a poison nugget on Nugget's route. Not really graphic and very short, but it's still there and has a sorta gross sound.
It depends on how you interpret it. There's a character who acts differently than everyone else who is bullied by the other students and the teacher, and he's (semi-forcefully) given pills that make him "normal"