Like any psychoactive drug, pot can alter how the mind develops, and there may be some physical developmental changes as well, at least in anyone under the age of 26-27 (this is when the last twinges of puberty and mental development are done). As such, it is very unwise to give pot to any minor for recreational effects.
That said, for a child with those conditions, the drugs that would otherwise be used instead of weed are very very harmful to a childs development. Because of this, a very many doctors will prescribe children marijuana for those disorders. And why not? Amphetamines are being given to children aged 5 now. Excuse me, did I say the generic "amphetamines"? That should be "Adderall" - because when the pharmaceutical company makes it, its not dangerous drugs
Please dont take this as sound medical advise; these are just observations I've made. Only your doctor can inform you when medical marijuana is right for you or your child, and every patient is different.