I came across this post the other day and it has some great information and advice: Kids and Depression. This is a topic so close to my heart, because I've suffered from depression since I was 11 years old, and because I see the same signs in my children. I know that they hear the same destructive voices inside their heads (because they frequently voice these thoughts aloud) and it scares me to death.
And so, I do the best I can with them and try to have them know that they are loved by God and by their parents. David has a counselor because of his Aspergers and I know that it is great that he has someone to talk to twice a month. The day may very well come when Isaac needs one as well. I know the teen years are only going to make things worse. I pray for their mental health every day.