I hope there isn't already a thread on this, I double-checked. Not entirely sure if this thread is in the right place either, apologies...

So, I know a little bit about them, but I keep finding the same information everywhere I turn. My main question is what causes them, and the information I've found so far seems universally ambiguous in terms of answering that question.

I'm relatively new in researching this, so any information or directions on good places to look for it would be quite helpful.

Also, if anyone experiences this themselves, a description of your particular symptoms would benefit me tremendously.