Sounds familiar here. My DS has a similar pattern with learning, though the lull periods usually only last for about 2 weeks at a time, so when he was younger, it was truly an exhausting pace. He also grows this way. Nothing, nothing, nothing... then an absolute constant need for food, followed by an inch of growth in the span of just a couple of weeks (and his legs hurt at night as you would imagine). As he gets older the effects from these mental and physical spurts are becoming easier to handle and his mood is becoming quite even. He can grab his own food as needed when he's extra hungry and when the brain is extra hungry he's becoming better at finding his own resources to deal with it (I do leave some challenging books laying around at all times just for this reason). Plus, his course work has gotten harder in school, so that helps.
Also, edited to add that I think any kind of growth can cause behavioral issues or mood changes in kids and that these can manifest very differently, from child to child. The bottom drops out for mine (the world is basically ending) if the blood sugar gets too low. Growing is just exhausting (even mental growth -- it takes real energy) and that means more sleep and calories may be required. However, with the excitement from the mental growth -- it may be hard to slow down and get those things.
Last edited by remalew; 10/18/12 10:48 AM. Reason: oops -- trying to answer OP
