This NYT story describes the strange case of Ashlyn Blocker, whose rare condition, congenital analgesia, prevents her from feeling physical pain. Stirring noodles, she drops a spoon into boiling water and reflexively plunges her hand in the pot to fish it out—she doesn’t wince, doesn’t suffer the mildest twinge of discomfort.

At first glance, this might seem like a desirable condition, even a talent or a power. We all want to be better at withstanding physical pain. And not feeling any hurt at all? That does seem like some kind of mystical ability. Kids at school ask Ashlyn if she’s Superman.

Those Man-of-Steel movies might’ve been a lot cooler if Kal-El’s undercover persona had been a 13-year-old girl who wears headbands and braces, plays clarinet and hawks her crocheted purses in study hall. But Ashlyn’s classmates were making a mistake that that many of us do when we first hear about—or even just imagine—a condition like hers. They were confusing insensitivity to pain with superhuman invulnerability to what causes pain.

Ashlyn and those who share her condition actually have greater vulnerability to injury and illness than those of us who feel the smacks and smarts of this barbed, hot-potato world. If you can’t register pain, you can’t develop natural aversions to behaviors that court serious injury.

When someone with congenital analgesia burns her hand or cuts her leg or fractures her ankle, the same damage is done as when a pain-sensitive person hurts herself. Tissue is torn, skin is seared off, bones splinter or snap. But the person often continues what they’re doing, blithely insensate, and the harm of the untreated injury spreads or escalates, sometimes to life-threatening levels.

One boy with the condition jumped off a roof to impress his friends, got up and felt fine. He felt okay the next morning too, right up until the moment he died of a cerebral hemorrhage that would have given most kids a headache the size of Hong Kong.

We all hate those throbs in the skull, but the brain pain that follows a serious concussion may actually save your life. It’s easy to forget the essential warning-sign role pain plays in keeping us hale and whole. When spasms flash red like the Lost in Space robot, you’d best hearken to that Danger, Will Robinson! Pain is the chief reason you’re turned off by things that you should probably avoid, like chewing razor blades or using your face to put out a campfire.

Pain can be sentry and sensei. It can protect and instruct, clue you in as it’s laying you out.

There are pangs that summon the stork and aches that ward off the reaper. In between the womb and the boneyard, our somatic Maydays rally all kinds of healing and restorative forces.

The same goes for many kinds of emotional pain, as long as you can find the source. Sometimes the origins of sadness or depression are as easy to spot as claptrap in a Klan flyer. Other times eruptions in your life have buried the causes under layers of cognitive slag—then it will take a little mental excavation to yield them up.

Depression doesn’t always have a discernible source. Still, it’s hard to know upfront whether a despondence that seems random on the surface is really causeless at full fathom five. A little introspection can help you suss out the substrata where the trouble starts.

Dull, blunt hurt might trundle into your mind driven by some toxic habit of thought. Maybe it’s ramped up by beliefs that defy your intuitive awareness, stunt your kindness, or douse your passion. Sometimes the pain starts as mental chafing against drudgery or oppressive expectations. Are you stuck in a job that saps your joy or flattens your spirit? Maybe you bought into a cultural myth of success, slaved to snare some shining grail, and instead found yourself clutching a scummy gutbucket.

In such circumstances, sadness and depression can be vital signposts. People who are congenitally bright-eyed, blinded by the solar intensity of their happy moods, often miss such tip-offs. They might stay in jobs or relationships or other scenes undermine them. Maybe you envy those whose sunny dispositions swamp them with so much light. But they run risks when they overlook or shrug off the dark pain that lays you low.

F. Forrester Church describes how Richard D. Lamm of Colorado was given to such pessimistic pronouncements that the press took to calling him “Governor Gloom.” His attunement to the meaning of ominous data helped him shape practical, efficient policy. Lamm used this parable to begin one of his speeches:

The Navy fleet is on the high seas. Suddenly a blip appears on the radar screen. “Tell that ship to change its course 15 degrees,” barks the admiral. The radio man complies, only to be signaled back, “You change your course 15 degrees.” Incensed, the admiral gets on the radio himself. “I am an admiral in the U.S. Navy. Change your course 15 degrees at once.” The word comes back: “You change your course 15 degrees. I am a lighthouse.”

Sometimes depression signals that you need a course correction. When you recognize this dimension of the illness, when you can decrypt the messages crackling out of the gloom, you’ll be less likely to steer your steamer into that rocky shore. You’ll lift your eyes and spy the beacon instead, then start charting your way to happier latitudes.

Researchers Andy Thomson and Paul Andrews have developed a theory about depression’s value as an evolved response to complex problems. Their “analytical rumination hypothesis” proposes that depression brake-checks us when the challenges we face require slow, sustained processing.

According to Thomson and Andrews, depression might improve our analytic and problem-solving abilities in a few ways. First, when we get bogged down, our chief desire is to helm the hell out of those brackish backwater moods. This sharpens our concentration on finding solutions to the snafus that stranded us there in the first place.

Second, while depression’s anhedonia seems like a curse, it can further enhance our analytic focus by removing temptations to run after pastimes our blue funk has drained of pleasure.

Finally, by siphoning our physical energy, depression keeps us off that kicky boulevard, away from diversions that can dilute our problem-solving attention.

Downtown’s distractions aren’t always a bad response to black moods. Sometimes you need to listen to the music of the traffic in the city, or linger on the sidewalk where the neon signs are pretty. It’s true that the lights are much brighter there. But it ain’t always smart to forget all your troubles, forget all your cares.

Lethe water might taste sweet, but it can give you a hangover. What you pitched toward forgetful oblivion can boomerang back at you as redoubled hardship. When the problems that seeded your malaise demand analysis and resolution, browsing books of laughter and forgetting might just stretch out your pain and push off your healing.

Most research on rumination, the defining thought process of depression, indicates its dangers. The chin-in-hand, eyes-on-ground, mind-in-circles cycle fixates on problems and thus deepens negative moods. So Andrews and Thomson’s idea that depression might serve long-term well-being bucks pretty serious research trends, even entrenched orthodoxy.

Jonah Lehrer’s New York Times piece on depression’s benefits surveys some of the most prominent criticisms the hypothesis has received, including Peter Kramer’s rejoinder about the crushing futility of chronic depression and “the self-hating, paralyzing, hopeless, circular rumination it inspires.”

Thomson and Andrews offer a measured response to critiques of their theory, acknowledging the “vast continuum” of mood disorders and ascribing usefulness only to depression that has a discoverable cause. Thomson is admirably pragmatic in his clinical applications of the hypothesis:  “That’s the litmus test for me,” he says. “Do these ideas help me treat my patients better?” The theory has given rise to some surprising therapeutic strategies, like his decision to cut back on prescribing antidepressants:

He now believes that the drugs can sometimes interfere with genuine recovery, making it harder for people to resolve their social dilemmas. “I remember one patient who came in and said she needed to reduce her dosage,” he says. “I asked her if the antidepressants were working, and she said something I’ll never forget. ‘Yes, they’re working great,’ she told me. ‘I feel so much better. But I’m still married to the same alcoholic son of a bitch. It’s just now he’s tolerable.’ ” The point is the woman was depressed for a reason; her pain was about something. While the drugs made her feel better, no real progress was ever made.

Depression might also enhance attentional capacity by activating a part of the brain called the left ventrolateral prefrontal cortex (VLPFC). Several studies show how “VLPFC neurons appear to promote attentional control by continuing to fire through periods of distraction and delay.” Since “people with experimentally induced depression or…episodes of major depression usually show a high neuroimaging signal in the VLPFC,” Andrews and Thomson conclude that depression might supply the kind of relentless, long-haul focus we need to resolve complex dilemmas.

Depression appears not only to increase attentional stamina, but to jack up analytic powers as well. You need a strong working memory to break down and resolve the knotty problems that bring on depression. Working memory, a kind of sedulous mental app, supports analysis by keeping loads of relevant data front and center. Since the left VLPFC mediates working memory, when the former is running on all cylinders, the latter also gets a turbo-boost.

But wait, you’re probably saying, What fucking mental stamina? What increased analytic power? When I’m depressed I feel like Hannibal Lecter has opened the top of my head, filleted my brain and fed it to me.

Well, yeah. “Rumination” does derive from the Latin for “chewed over,” after all.

It’s true that the Big D mashes your mental abilities for a while. Bathing or getting dressed might suddenly seem as daunting as rocket science, lunch out with a friend more nerve-wracking than a bar exam.

But according to Thomson and Andrews, even depression’s well-known cognitive deficits might sometimes serve an adaptive purpose. Rumination shunts so much of the mind’s voltage off to power analysis of gnarly life problems that’s there’s scant intelligence left over for anything else.

You’ll have to judge for yourself (or together with a therapist or friend) when jazzy distractions will help and when it’s better to dive down and scout out depression’s causes in the murky ocean-floor minestrone. Sure, it’s scary to spiral down there among the eel grass and brain coral, the hacked creatures and deep-sixed wreckage of your life. But consider how plying these doldrums might have a meaningful, ultimately healing and revitalizing effect. Recognition of such purposes might even speed the undersea analysis that will resolve your snarled, draggy problems.

Eventually you’ll be finning back up toward that spangled surface, that luminous air.