Autism is a structural difference in the brain with a strong genetic component. People on the autism spectrum have brains that don't go through the normal culling of brain cells after birth that neurotypical brains do. Although autistic brains do go through a culling at a later age, they tend to be denser than normal brains with more brain cells.
People on the autism spectrum tend to have sensory processing differences. Some are highly sensitive to loud noises, colors, textures, or other sensory stimuli and are called "sensory avoiders" because they try to get away from stimuli that are too disturbing. Others on the spectrum are called "sensory seekers" because they pursue high levels of sensory input by, say, eating spicy foods or running around and crashing into things. Sensory seekers seem to need proprioceptive feedback in order to calm down and re-equilibriate.
***EDIT: I should probably post this information here. Most children with sensory differences have some sensory seeking and some sensory avoiding behavior. See discussions in the comments for more information.***
There are places that sell compression vests and jackets, sometimes with weights. Those can run about $50-150. Compression vests are more for long term wear, say during the school day to help sensory seekers feel secure and able to concentrate.
This is a quick fix that works for us when my 3 year old can't seem to calm himself. I can't always drop everything and give him deep pressure massage for 20 minutes if he's freaking out, and this is another option.
Note: if you feel the urge to leave a comment or send me a note about how you heard that autism is caused by vaccines, poor nutrition, gluten intolerance, food additives, or poor parenting... just don't.
Step 1: Secure the items
nylons or tights
a sensory seeker toddler who is starting to get hyper, possibly running around, dumping things out, throwing things, and/or hollering
This sounds easy but sometimes it's tough to find a pair of tights when there's a 3 year old tornado in your house. My only advice is to hurry. When you have your pair of tights, pick up the toddler and hold him tightly. Don't yell or act angry; he's not trying to be naughty, and your yelling will make his brain freak out even more.
When he's still enough for you to begin, hold one foot of the tights by his right armpit and over his left shoulder. Pull rather tightly, but not tight enough to bruise. When the tights are back to his right armpit, simply wrap them over the loose foot end to secure it. Once you've reached that point, the rest of this should be pretty easy.