My doctor has only mixed ssri's when I was tapering off one to start another, so I don't know why someone would be on multiple ones at the same time. But it's not uncommon for people to be on a combo of meds from different classes, like adderrall or wellburtrin and an ssri, since one med is not the same for everyone and often it is the combo that works the best. Plus, it is true that depending on the person, the underlying issues can't always be reached until you've treated the symptoms. Everyone is different and everyone doesn't get addicted, especially if they have a responsible psychiatrist.