Many of the tumultuous moods that we think are normal by-products of adolescence may be signs of depression. Symptoms of depression should not be confused with or dismissed as adolescent mood swings.
When attempts at helping your children are ineffective, then it is advisable to seek professional support, especially if the following symptoms persist for several weeks, become more severe, and/or lead to self-destructive thoughts or behavior. The following symptom list has been developed by the National Institute of Mental Health:
Persistent sad or “empty” mood, feeling hopeless
Loss of enjoyment or interest ...