Geofruit also makes a great way to improve mood. They're really common, and taste good.
Yeah, this game seems to have lots of ways to change emotional state, like seeing corpses, eating something yucky, going through withdrawal getting hurt, or even just sleeping on something uncomfortable will make your character sadder, while taking your time, eating tasty things, and consumption of drugs makes you happy. I'd imagine that also communication with the survivors makes you happier, I just never really checked.