Sadness that persists for more than 2 weeks
If your child is sad for longer than two weeks, they may be dealing with depression. Many don't realize that depression can begin at such a young age. While it is not as common as the development occurring in early adulthood, it is possible.
Parents often dismiss this sadness as normal "angst," but it is best to have your child speak to a professional if the sadness does persist for over two weeks in case it is depression. After all, catching it early and having your children learn positive coping mechanisms will be powerful in the years to come if it does turn out that depression is the cause. Even if there is no sinister mental illness causing the persistent sadness, no harm can come from your child talking to an expert, as it is a very beneficial thing to do even for those who are of perfectly sound mind.