I literally used the phrase "serious issue" in the proceeding sentence to describe the situation.

??? I'd be very curious to hear this one explained. I'm totally baffled.

You are mistaken about depression not having observable effect on the body. I wrote a post about that; it's a direct sibling to your original post.

Your point is a bit conflicted. Like this person pointed out, it seems that you're saying that it's serious and not that serious at the same time.

However, I think that the observation you wanted to convey wasn't about the comparative seriousness of depression, but rather that it's in some sense in a different realm than for example AIDS or shingles, even if the realm of some of its effects are similar (which you argued against, but you're wrong). And, I sympathize with that. Depression does seem to be made of a different cloth, but it's quite hard to elaborate further, and I won't get into it here.

It is odd to mention shingles in this context, as depression is a very common symptom of herpes infection, actually fixed by antiviral medication.

So, even on its own terms, the argument is incoherent and, not to put too fine a point on it, wrong.