If so, what is the mechanism for this perceived improvement of autism symptoms following treatment with cannabis products? Is there a downside to this approach?

You saw intuitively the reason quite clearly. It is, in fact, a dumbing down of these individuals causing their seeming normality. It is somewhat paradoxical and counterintuitive to see individuals who are somewhat erratic in their behavior and have trouble communicating and seem often to be hyper-stimulated who then seem to relax and have periods of greater calm enabling normal functions to proceed unimpaired, as being a good thing, but in actuality, it is solely through a kind of numbing effect of these agents—it is a reduction in cognitive function that results in the calm state of being. We would consider this a liability, more than a benefit, and moving in the wrong direction. The use of chemical substances has often been turned to as a coping mechanism for emotional states of unpleasantness and lack of control, to subdue people who might harm themselves or others and also the great many who are simply unhappy and quite miserable because they feel out of control and their thoughts get them into trouble and certainly keep them wound up, and overstimulated, and hyper‑focused on problems created by their own mind in many cases. This is the consequence of overattention and a hyper-focus on potential negatives—they will loom much larger and this may be quite inappropriate, but nonetheless preoccupies the person and distracts them from dealing with the normal everyday events of life. Internally, their mind is racing and they are continually addressing potential calamities. The fact these do not happen in actuality does not spare them from the effort they make continually to make sense of their interior world as the mind bombards them with so many perceptions of things they do not know how to control, and can easily be overwhelmed. To have that quieted down is, in one sense, a benefit but in another, taking away their keenness, the edge they have in seeing things with greater than normal clarity and having the mental ability to examine them and consider the many possible ramifications with a thoroughness and depth that is supernormal. This is what such individuals are doing in their thoughts when they seem out of touch and are exhibiting odd behaviors—it is that their mind is running away with them through its great power and they are simply barely able to hold their own and blend in while being so preoccupied. There is a loss for them when this keen intelligence is dulled through a pharmacologic manipulation. It may make them feel calmer and more a part of things but this does come at a cost and it is certainly changing them from who they are. When old enough to make a choice for themselves, this can be offered in good conscience, but for the young who do not understand their dilemma, to begin manipulating them in this way is unfortunate because it will take away their individuality and alter their very being in a deep sense. It is rarely possible to judge the overall value in the sense of the long-term consequences. People will simply have to do the best they can and we understand there will usually be a vote heavily on the side of using the drugs to create a behavioral change deemed of value. The long-term use has yet to be studied carefully but when it has been, there will be clearly adverse events noted again and again with a long-term liability from chronic use of these substances. So it can be an adjunct done with safety for temporary conditions but is not a good answer for a well-entrenched alteration of an individual to make them different. That is part of their nature and will persist unless it receives divine healing sufficient to shift things back into the positive range—that will rarely happen for most because of the unappreciation of the power of prayer and the inability to pray effectively in most cases. So this problem is being created by the practice of medicine in allowing increasing use of cannabis and its products without adequate long-term safety studies in place.