The causes of autism are unclear, but the signs may be observed as early as three years of age. Because the causes are not understood, there are no medical treatments available for autism. However, there are complementary and alternative medicines that are said to have positive effects on autism. One such system uses magnesium and Vitamin B6.
Magnesium, with the chemical symbol Mg, is the 4th most abundant element by mass in the body. Magnesium ions are important to the function of all living cells, not just in upkeep but also in growth and development as well. The majority of the population does not receive sufficient amounts of magnesium from their diets. There have been studies noting the lack of magnesium in the bloodstream for autistic children [2,3,4,7].
Vitamin B6, also known by its other name “Pyridoxine”, is used in metabolic processes for proteins, glucose, and lipids. It is also important in histamine synthesis, hemoglobin synthesis and function, gene expression, and – perhaps most relevant to this discussion – neurotransmitter synthesis.
Some people advocate the use of high doses of Vitamin B6 and magnesium to correct autism. However, note that there is still a difference between high doses and overdosing. For magnesium, the upper limit dosage for 4-year-old to 8-year-old children is 110 milligrams per day,  although one study, using 200mg of magnesium showed no significant side effects. [11,16] As for Vitamin B6, the maximum recommended dosage for children age 4 to 8 years of age is 40 milligrams per day.  One study, in children with epilepsy, who had been taking 900mg of Vitamin B6 for 6 months showed no significant side effects . 
The theory is that in autistic children, a certain enzyme that works to break Vitamin B6 to its biologically usable form (pyroxidal-5-phosphate) doesn’t work as well. This derivative of Vitamin B6 is required in the synthesis of dopamine, which affects many behaviors and is linked with feelings of pleasure.
The idea is that by supplying the children with a greater amount of “raw” Vitamin B6, the higher the eventual converted amount, which may then allow the child’s Vitamin B6 levels to normalize and rise.
As for the high doses of magnesium, it is simply an effort to bring the child’s magnesium levels up to normal, thus paving the way for the normal level of activity expected from processes requiring magnesium ions.
There were at least 4 studies conducted on the efficacy of Vitamin B6. Of the three most widely published ones, 1 showed an improvement in verbal IQ , while the other 2 studies did not note differences between the placebos and active treatments [8, 9]. These three studies were criticized for using such a small sample population – they had only 8, 10, and 15 subjects respectively.
An autism treatment study using the same combination of magnesium and Vitamin B6 was conducted. However, this study showed no reported positive or negative results. 
From our research, there were at least 4 other autism research papers involving the use of Vitamin B6 and magnesium [3, 11, 12, 13]. While these studies did report positive behavioral effects, there was some criticism over some possible bias and the method of execution. The researchers in these studies knew which subjects got the treatment and which ones got the placebo, so there was the probability that the results were biased.
While hope for a cure for autism is rare, this treatment seems to have a positive effect on about half of the children that take it, and even within that successful population the degrees of efficacy vary.
However, given the fact that Vitamin B6 and magnesium supplements are very affordable, there is little reason not to try the treatment. The monetary risk is low, and if the treatment seems to be ineffective, the supplements may still be consumed normally and magnesium and Vitamin B6 have so many other health benefits. In addition, these supplements can improve one’s ability to cope with stress and also improve the quality of sleep.
As mentioned previously, there is a strong need to remember to keep the dosages in check. There may be the temptation to up the dosage in the hopes of accelerating the process or causing a stronger effect, but this could put the health of the child at risk. Remember the dosage guidelines and stay below the upper limit.
A great source of magnesium is Mag365 Kids. This formula has been available for many years and is manufactured by Peter Gillham whose magnesium products are the best selling magnesium products in the United States - selling 6 times more than the next best competitor for many years in a row. This formula also has Vitamin C and zinc in it for proper DNA formulation.