5. Genetics
Genetics also play a role in sleep paralysis. A study looking at causes of sleep paralysis got responses from me huge pool of siblings, including many twins, and those responses demonstrated that genetics is partially responsible for sleep paralysis.
If someone in your family experiences sleep paralysis, then you have an increased chance of having at least one episode yourself.
A genetic predisposition towards sleep paralysis combined with some of the other causes listed here can make it almost a certainty. Those who are prone to sleep paralysis should minimize their chances as much as possible by avoiding alcohol, drugs and sleep deprivation.