I was shocked and deeply saddened when my daughter announced at the dinner table that Robin Williams had died of an apparent suicide. My wife and I and the three of our children home at the time all pretty much gasped audibly in unison, and then for a moment after, you could have heard a pin drop.

For a bit after that, we talked about our shock and sorrow. And then after that, we talked about all the joy Robin Williams had brought us over the years. For our kids, that came via his more recent and/or indelible performances, such as Mrs. Doubtfire, and Good Will Hunting. For my wife and me, it was that along with memories stretching back decades to the early, frenetic, and clearly brilliant Robin Williams of Mork & Mindy days.

I did not know Robin Williams personally, and have no unique claim to the grief so many of us share at his untimely death. I had heard, as had we all, about his intermittent struggles with addiction and recourse to therapy over the years. I had hoped, as I suspect we all had, that the demons in question had been slain. Allowing myself to believe what I hoped to be true, his death did indeed come as a shock.

No doubt even as I write this, mental health experts are on the morning shows, joining in carefully crafted memorial montages, and offering tips about the signs of, and treatments for, depression. I hope that does some good, although Robin Williams’ family likely knew a bit about both, and yet it came to this. Either way, I will leave that to them, and instead contribute something from personal observation — and the music of Smokey Robinson.

As a clinician for the past 25 years, I have gone through the distinctive choreography of clinical care thousands and thousands of times: meet a stranger; exchange greetings; enter an exam room; close the door; and dive into their every intimacy.

The Spider Man movie adage — with great power comes great responsibility — comes to mind whenever I think about. We might add great privilege into the mix. The physician’s privilege, power, and responsibility are to have access to those private truths most of us keep under the cover of public veneers most of the time. Physicians are invited in under the skin.

The results are stunning. Innumerable times, I stood in the hall of a clinic and greeted a composed, well dressed, apparently successful, emotionally stable adult — likely the envy of their peers. And then behind the closed door of the exam room, that person would come undone, and tell of sexual assault in childhood by a family member; drug use by a child; beatings by a spouse; struggles with addiction. This is not true of everyone, obviously. But even after all these years, I am little less than amazed at how common it is.

More importantly, I can guarantee you that unless these people are your most intimate friends, you have absolutely no idea who they are. Unless, that is, you are among them.

These people are everywhere, and some of us are them; some of them are us. Those of us who aren’t them — and I note that I am not, having lived a truly privileged life surrounded by good and loving people — are certainly interacting with ‘them’ every day. We just don’t know it.

But they could easily be the person we argue with over not much of anything. They could be the person at whom we hurl insults through cyberspace. They could be the person we give the finger (or “flip the bird” as my kids say) while driving.

In general, it’s just very easy to presume that the person annoying us in any given moment is fair game for our various vituperations. But maybe that annoying driver is wiping tears from his face. Or trying to see clearly through her swollen eye. It’s true more often than any of us would like to acknowledge. I know, because they tell me.

Robin Williams was a clown, a brilliant clown. Yet all the while he was making us laugh, he was presumably wrestling with depression and its attendant demons. All of us he made laugh share in this moment of poignant grief, collectively inclined, I suspect, to think of Smokey Robinson’s words: “Ain’t nothing sadder than the tears of a clown.”

Maybe a heightened awareness of the insidious dangers of depression will result, and make some good of this tragedy. But there is another opportunity here for us all.

Mr. Williams was a far better actor than most of us, so his veneer was more elaborate. But all the world’s a stage. Such veneers abound. Perhaps we could keep it in mind, and give one another the benefit of prevailing doubt. Under our skin, and past the surface where the show goes on — there is a lot that is routinely unseen. The scars of shared adversities, a parade of triumphs and disasters, and the deep bonds of our common humanity, reside there.

David L. Katz is founding director, Yale-Griffin Prevention Research Center. He is the author of Disease-Proof: The Remarkable Truth About What Makes Us Well.