It's nasty because of the assumption that someone who is taking medication has "buried the cause further", in other words, done something to paper over the rent in their psyche that could have been fixed some other way.

In my case, I had depression for no apparent reason, and I went through dynamic psychotherapy, which is basically about finding that reason. That failed, I got worse, and basically was disabled after a few years. I finally found a medication, venlafaxine, that actually worked. My depression abated, I was no longer disabled. It has well-known withdrawal effects, so I tapered off of it very gradually. When I stopped, I was no longer suffering major depression. There was no removal of any particular cause.

There are lots of people depressed for no reason. Look up Winston Churchill and his depression for a public example