Disease vs Syndrome
“A syndrome is a recognizable complex of symptoms and physical findings which indicate a specific condition for which a direct cause is not necessarily understood. Thus in practice doctors refer to the infamous “viral syndrome” as such because of the uncertainty regarding the legion of viral agents that is causing the illness. Once medical science identifies a causative agent or process with a fairly high degree of certainty, physicians may then refer to the process as a disease, not a syndrome. Mucocutaneous lymph node syndrome became Kawasaki syndrome which in turn metamorphosed into Kawasaki disease; the latter is properly a disease, no longer a syndrome, by virtue of its clearly identifiable diagnostic features and disease progression, and response to specific treatment.”
https://pmc.ncbi.nlm.nih.gov/articles/PMC1480257
Post SSRI Syndrome (PSS) vs Post SSRI Sexual Dysfunction (PSSD)
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.