Parents become confused when trying to choose the best diet for autism. The wisest choice is a diet backed up with sound science and that would certainly apply to SCD.
SCD is based on scientific evidence that bacterial toxins are linked to ASD. Mice who get bacterial toxins display the symptoms of autism. SCD is effective because it is the the diet that is designed primarily to eliminate bacterial toxins.
Bacterial toxins produce many forms of brain injury; opiates is just one.
Other well known diets for autism treat various issues that are are also caused by bacteria. There are bacterias responsible for Hypoglycemia, high levels of ammonia, and for creating the conditions that make oxalates a problem. Bacterial toxins affect the leaky gut, brain body barrier and opioid sensitivity. Pathogenic bacteria also make it possible for yeast to thrive in the body.
The best approach is to get rid of bacteria that are causing the damage rather than to just treat symptoms with other diets. Eliminating bad bacteria is the basis for SCD.
The following links will explain why scientific research backs the SCD rather than the other diets.