This website from BetterHealth covers symptoms of depression in young people, causes of depression in young people, treatment for depression in young people and where to get help. Symptoms of depression in young people include feeling grumpy, having trouble sleeping, feeling worthless or guilty, eating more or less than usual and gaining or losing weight. There is no single cause of depression, but it can develop from life events, genetic dispositions, hormones, or any combination of those factors.