Does it work?
There is some controversy surrounding the evidence for the effectiveness of vitamin B6 and magnesium in autism (12). Two small but well-controlled studies showed no effects, positive or negative, of combined vitamin B6 and magnesium therapy (14, 15). One larger, but less well-controlled study showed positive and significant behavioral effects of combined vitamin B6 and magnesium, but not vitamin B6 or magnesium alone (14).
Additional studies showed that vitamin B6 and magnesium had significant positive effects on behavior in children with autism (3, 8, 16, 17). There were, however, major problems with the designs of these studies. In particular, the researchers in these studies knew that the children were receiving supplements. Therefore, their ratings of the children's behavior could be biased. However, one of these studies did include another small, double-blind, portion suggesting that vitamin B6 and magnesium therapy can improve behavior in some children with autism (16).
The difference in outcomes of the various studies could be because vitamin B6 and magnesium results in positive behavioral effects for about half of those who try the therapy (18). Another explanation is that vitamin B6 and magnesium supplementation is not effective. The better-designed studies suggest that this may be the case, although these studies were so small, it is difficult to draw conclusions from them (12, 18).