Why might sleeping on the floor alleviate PTSD symptoms?
Question: Does sleeping on the floor have similar neurotransmitter effects, as sleeping under a weighted blanket might? Psychiatrically, would it be expected that a person having PTSD would find similar results sleeping under a weighted blanket as they do when they sleep on the floor?
There is also a lot of consensus on how weighted blankets seem to help alleviate these symptoms, providing that sense of security. They also seem to be used a lot by parents of children with Autism, Aspergers, and ADHD.
Could sleeping on the floor also be related to this, possibly because of the firmness and sense of security felt from being on the floor? (Even if physically uncomfortable.)
No. Don't connect those very different studies and use it as a basis for a conclusion.
The article you reference mentions the word "floor" 3 times, twice to mention that 2 children sleep on the floor and the third time the author writes:
"Children who sleep on the floor instead of their bed after a trauma do so because they fear the comfort of a bed will let them sleep so hard that they won’t hear danger coming.".
It is the claim, of proponents of weighted blankets, that they: reduce movement, let you feel as if you are being held, and thus promote better sleep.
Source: "What's the deal with weighted blankets?":
"The thought is that this weight mimics the pressure of being held, which helps release anxiety to let you fall asleep faster. Some studies, including a 2015 one "Positive Effects of a Weighted Blanket on Insomnia" from the Journal of Sleep Medicine and Disorders, back this up (.PDF). The research found that weighted blankets did in fact provide a "beneficial calming effect" for those suffering from insomnia.
In case one it is the decision of a few children that they won't sleep as well, in the second case it is businesses that want to sell weighted blankets to cause you to sleep better. Opposites.
References on beds such as Wikipedia's "Bed" webpage or Mattress Mart's "History of the Bed" ;) attribute the invention of the bed as a means to increase comfort. One must also consider pressure ulcers caused by insufficient padding and reduced movement.
Comparing misread articles, few in number, and extending it to other unreferenced articles and ailments isn't a supported basis on which to advance a theory on psychology involving biological, behavioral, cognitive and social disciplines.
Prior to 3600 BC mankind did without bedding.
Source: "History of the world - Early Humans":
The closest living relatives of modern humans, Homo sapiens, evolved around 4.6 to 6.2 million years ago. Anatomically modern humans arose in Africa about 200,000 years ago, and reached behavioural modernity about 50,000 years ago.
By the reasoning of your theory and extension of those two prior paragraphs one would conclude that prior to 5620 years ago there were no PTSDs, it is the modern bed that is a contributing factor.