Since the sightings stopped after the bridge collapse, and one sighting was over the bridge just before the collapse, some paranormal investigators theorize that the mothman was actually some type of psychic projection.
Some experts theorize that another possible cause of school refusal is traumatic and prolonged separation from the primary caregiver in early childhood.
However, many experts theorize that environmental factors may play a role, triggering the disorder in those with certain genetic vulnerabilities.
Some researchers theorize that pollutants in the environment may interact with genetic weaknesses to trigger ASD.
Because of this, many researchers theorize that migraines are caused by an overabundance of naturally occurring brain substances that that cause blood vessels to swell and press on nerves in the head.
Some protesters of clay litters even theorize that bentonite can coat the intestines, preventing the absorption of nutrients and causing an overgrowth of unhealthy bacteria.
Even though it's science-fiction, the wormhole theory is a popular one that many theorize could also allow travel into other dimensions or parallel worlds.
Mitochondria are components in cells that create energy, and some theorize that mitochondria dysfunction in brain cells may lead to the symptoms of autism.
It's not clear why or how it worked, but scientists theorize that the acetic acid turns on genes that produce enzymes used by the body to break down fats.
They compelled a man like St Paul to theorize: thought was driven inward; it was made to search for foundations, to organize itself and knit together part with part.