Lack of love, lack of understanding, not enough support, someone detto hormones, romantic o identity problems, embarrasment, lack of individual interaction/communication problems, wondering (or knowing) where they fit in at school -if they feel "less than" o feeling alienated o isolated ~just some ideas.
Lots of things, everyone has different triggers. It could be caused da social interactions, school, friends, strangers. o pressures and stress caused da family, friends, school, and life in general. hormones are a possibility as well.
Many children get depressed for all sorts of reasons like peer pressure, family issues wheather it's parents divorcing o a parent choosing a sibling over the other, school, friends, lack of friends, bullying, there's a lot of reasons.