As a side note, have you had him checked to see if he has any or all of the following?
1. Hypoglycemia
2. Thyroid issues
3. Pituitary issues
I've had intense mood swings and rages my whole life, so bad that many doctors wanted to label me bi-polar. I've resisted the diagnosis because I don't believe it's accurate, I've always known it was something else wrong. Turns out through testing that I do have hypoglycemic episodes, my thyroid is not functioning, and I probably have pituitary function issues (testing just started there). When the hormones are off, the whole body goes crazy. Just something to think about. Oh, and if he's having blood sugar crashes, that can cause severe mood swings and outbursts.
I hope everything works out for your son. I was in a treatment program for 5 weeks for depression last year and it was one of the best decisions I've ever made.
I can second the intense impact hypoglycemia can have on a child's moods. My son is hypoglycemic, but we didn't figure it out until his father went on the South Beach diet, the whole family cut out sugar and carbs, and suddenly my son leveled right out. And then the first time sugar was reintroduced into his diet, he fainted.
But, I really used to worry about that boy's mental health. In kindergarten he was saying he wished he was dead. He'd get frighteningly depressed, and then a few hours later be screaming and banging his head on the floor so hard he was giving himself bruises and scabs. We worked hard on self control, but it really hurt to hear him saying he was "never happy". He would cry, and laugh, and keep crying, all at once. Holidays were especially hard. We used to joke about the inevitable holiday meltdown - I think every Christmas I could remember began and ended with him sobbing hysterically. He kept saying, "I can't stop!" and I'd tell him "You can!" Sometimes it seemed like he would almost pass out from the effort of trying to hold it all in. A friend of mine was convinced my son had an anxiety disorder like her teenage daughter. Other people used to ask me if he was autistic.
And then he starting eating a low carb diet and it was like the sun just came out. He's relaxed and happy, and he even *looks* healthier. His face always seemed kind of puffy and pale before, but now he's slimmed down and there's more color in his cheeks. You can see the difference in his school pictures.
I never would have guessed that something as simple as the right diet could make such a huge difference. He ate a good diet before! But for this kid, bananas, watermelon, whole wheat bread, potatoes, and spaghetti just aren't things he can eat regularly. He needs meat, veggies, cheese, and occasionally a bowl of berries.
In addition to looking into psychological issues, it's always worth considering whether there are hidden medical issues as well.