It turns out that Henry does have a genetic issue going on. We had him do the MTHFR test (a simple finger prick). Apparently his C671T allele (the larger one) is normal, but his A1298C is homozygous. It is missing the allele from each parent. It means that his body's ability to process folic acid is decreased by 30%. The psychiatrist explained that it's as if he only has 70% control of his behavior (because our body needs to process folic acid properly in order to support the production of important neuro-transmitters that are connected to self-regulation). (Editor's Note: All of this is coming from my scribbled, hand-written notes, so any part of this is not necessarily 100% accurate; it's a lot to follow!). Apparently this gene is linked to all sorts of things like addiction, depression, anxiety, thyroid issues, and heart disease.
She prescribed him L-methylfolate, which is folic acid that has already been more processed for the body. He takes 15mg a day. For the first week and a half, it seemed to cause him headaches. I was worried that it was too much for his little body and thought about stopping it, but part of me wanted to keep him on it for at least 6-8 weeks, which is how long she says it takes to see its full impact.
There was one day when we ran out of the pill (between the samples and his actual prescription). He didn't take it in the morning like he normally does. That afternoon, he had the kind of fit that he hasn't had in several months. The next morning, we gave him his pill like normal. The next morning, he woke himself up, got himself dressed independently, and then made breakfast for himself--all before we even got out of bed. I know this evidence is entirely anecdotal and completely unscientific, but it's the only data I have, and I'm compelled to keep him on it.
I'll keep you updated about how it goes for us!