How can you interpret tens of bad drawings (dinosaurs eating people, bloody swords, scary faces, mummies...) of a teenager associated with day dreaming and lack of energy?
Drawings like that are pretty normal among boys. (I mean what else would a dinosaur eat). The drawings probably reflect the movies or tv shows or comics he sees. I would be more concerned about the day dreaming and lack of energy. Does he stay up late at night? How are his grades doing?