What happens because of Charlie's New Year experience?

Charlie's bad experience with LSD forces him and his family to confront the darkness that has been present in Charlie's mind. Even more is revealed about Charlie's mental state through his parents' reaction to his hospitalization. Even though his parents do not realize that Charlie took LSD, they do not probe as to why he was found outside in the snow. It seems possible that Charlie could have made this decision without drugs, and therefore Charlie does not need to tell them that he tried LSD. Their response shows just how frayed Charlie's mental wellbeing is.