The building blocks of mood disorders-(Major Depressive disorder)...
Major Depressive is indicated by at least two weeks of depressed mood or a loss of pleasure in most activities. Depression in children may be presented with irritability instead of sadness, or a combination of both.
Some symptoms include...
Change in appetite, loss or gain of significant weight
Insomnia or hypersomnia
Restlessness or agitation
Fatigue/lack of energy
Difficulty thinking, concentrating and making decisions