Quite a lot of us have children or relatives with autism, and many of us have had B12 issues. This study, pub in Feb this year, lead Robert Hendren, easily found on Google, gave 25 asd children B12 injections and 25 a placebo injection. There were measurable improvements in the B12 group, and bloodwork showed improved cellular methylation.
There has been a lot of anecdotal evidence of B12 helping a substantial proprtion of ASDs, and one study found low B12 in ASD brains. As with us, no doubt getting all nutrients optimal will help, including D and iron, and many say B12 should be taken with a good B complex. But it may be worth trying sublingual B12 with the B complex on an ASD child and seeing if there is improvement, this study adds weight to the idea that it is worth a go. I thought with my son that there was an improved eye contact with methyl folate, which I gave first, and that there were marked improvements with B12. But these things are very subjective and behaviour is changeable anyway. Hope this helps someone.