[markroseman]

Being on more than one antidepressant is not unusual, and can even sometimes be optimal. Even ones acting on the same neurotransmitter often target different receptors and hence different symptoms. More often it's because doctors are better at adding drugs rather than taking away ones prescribed by other doctors "just in case."

Serotonin syndrome can be an issue with all kinds of things (most people aren't warned about being on a SSRI and having cough syrup for example), but is not very common in practice, and because it coincides with a change/increase in medication, often sorted out quickly, even if it's characterized as a "side effect" or "tolerability" problem and not actually recognized for what it is.