It is very weird. I would say that in my experience dealing with people with PSSD that they tend to be 16-24 years of age when taking the drug (although that may be due to who is going online to talk about their struggles). I run www.pssdforum.com and moderate the www/reddit.com/r/PSSD subreddit, and those collectively have few hundred members. The older yahoo page used to have a few thousand, and this doesn't include the many many people who message me on Reddit telling me that they are noticing this too.

So even if 10,000 people (a high estimate) had it in america (where I live), that may only be 1% of all the SSRI users. So overall it is pretty unusual for it to stick.