Post SSRI syndrome (PSS) is a condition that includes a variety of symptoms that appear after taking an SSRI.
The condition may appear after increasing or decreasing SSRI dose, or after long time use or discontinuation of an SSRI. It may appear after taking only one dose.
PSS might be the same condition as PSSD (post SSRI sexual dysfunction). Assuming it is, PSS is a more appropriate term that doesn’t make emphasis on sexual symptoms.