F.H.
Try Bach Rescue Remedy. It's made from a blend of flower essences and helps with many emotional issues like stress and depression. I think I've seen a kid's version advertised in KIWI magazine. There are also homeopathic remedies and vitamins just for kids to help their immune systems. Go to Wholefoods, or any health food store hang out in the supplement section, and find some help.
I know some people think it's crazy, but you might want to search for a non-traditional "therapist". Someone who does Reiki, or is trained in healing and balancing the human energy field and chakras. I've known MANY kids who had emotional issues respond wonderfully to these therapies. To me, doping kids with pharmaceuticals sounds much crazier.
Take him to swim in the ocean, touch some dirt and start a gardening project, go for bike rides. Butterfly World is GREAT for relaxing (if he's not afraid of butterflies - duh). Get him a nice hat and try to get him to wear UV filtering sun glasses.
Lastly, you need to clear your home of negative energy. I think Wholefoods sells a type of sage incense for this purpose. They call it "smudging".
I wish you much peace and hope Banyan feels better soon.