Medications all involve changing/adjusting levels of chemicals, enzymes, proteins, gene expression, etc. in the body. We know so little about how/why ASDs often involve hypersensitive sensory systems to begin with, and since the chemicals/enzymes/proteins/gene expression involved with sensory systems and their receptors all act based on environmental stimuli, there really isn't even a feasible way to medicate sensory overarousal. Like, the only reason the signal transduction cascade in the eye's photoreceptors begins is because photons in the environment caused a chain reaction. The only real way to stop the sensory receptors from reacting is to stay away from bothersome stimuli, which is probably why you only ever hear about occupational therapy being used to treat/manage SPD.
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Helinger: Now, what do you see, John?
Nash: Recognition...
Helinger: Well, try seeing accomplishment!
Nash: Is there a difference?