Whenever I approach a high-up balcony railing, or look over some cliff, I get this urge to jump. It's even got a visceral component: that sub-solar-plexus twinge, if you know what I mean. I have to step away quickly, or hold on tightly. I'm just average depressed. What's going on?
—Norbert Hirschhorn, London
You and Edgar Allan Poe both, doc. (Er, doctor—the letter-writer is the well-known co-inventor of a lifesaving procedure known as oral rehydration therapy.) In slightly more flamboyant language, the author described a similar sensation in an 1845 short story: "[B]ecause our reason violently deters us from the brink, therefore do we the most impetuously approach it. There is no passion in nature so demoniacally impatient, as that of him who, shuddering upon the edge of a precipice, thus meditates a Plunge."
Poe called this feeling "the Imp of the Perverse." Of course, Poe was the kind of guy who would go in for a little macabre perversity. But what's it mean for the just-average-depressed?
More broadly, folks interested in the workings of the brain have used the imp as an entree to explore human tendencies to engage in, or at least entertain, the idea of behaviors—say, jumping off the Golden Gate Bridge—that seem to run counter to our self-interest. Emile Gabriel Bruneau, an MIT neuroscientist writing in Psychology Today in 2013, suggested the imp may dwell in the medial prefrontal cortex, a region of the brain that plays a role in decision-making and impulse creation. Just as important, though, is the lateral PFC, which is thought to "shackle" the imp, to borrow Bruneau's term—so damage to this area, eroding those shackles, can lead to a loss in impulse control. Bruneau relates the story of a man who developed a sudden, inexplicable desire to view child pornography. After doctors found and removed a tumor in his orbitofrontal cortex, the urges dissipated. (Unfortunately for our protagonist, the discovery of the tumor came on the eve of his court sentencing.) When, a year later, the man began again to contemplate pedophilia, a return trip to the neurosurgeon revealed that a small bit of tumor had been missed the first time and regrown. Relatedly, people with frontotemporal dementia often get into trouble with impulsive behavior that runs afoul of social norms—indecent exposure, undisguised shoplifting, etc.
What's important here is that, under this theory, different regions hold each other in check, impulsewise. In Bruneau's telling, the lateral PFC acts as the brakes of the car that our, er, shackled imp is driving (here's hoping this guy works an EEG machine better than he works a metaphor), and it's the medial PFC that supplies the gas. These elements together, Bruneau suggests, "may keep behavior in balance." Which is why, among many other reasons, it's a bad idea to mess with the relevant hardware unless you have a good idea of what you're doing: Frontal lobotomies did remove unwanted inclinations, but they tended to remove all your other inclinations, too.
So, one part of the brain suggests you jump, while another, ideally more persuasive part strongly favors the alternative. But this doesn't explain where that bizarre urge comes from in the first place. A 2012 study published in the Journal of Affective Disorders proposes it involves a different area of the brain: the amygdala, which governs "fear circuitry." The authors, Hames et al., term the experience you describe "high place phenomenon," or HPP—the strong impulse to leap off a balcony experienced by both the suicidal and those who aren't even feeling particularly depressed. Researchers surveyed subjects with and without histories of suicidal ideation regarding their experiences with HPP. They found that about 3/4 of ideators reported getting the urge, but, significantly, so did more than half of those who'd never thought of suicide.
Why did all those apparently nonsuicidal people feel like jumping? The researchers guess that it has to do with the way in which humans' several systems of perception, which usually operate well in tandem, can get knocked out of whack by your basic high-place-type situation. Briefly, they propose that an unconscious instinct for self-preservation kicks in before you've consciously reckoned with a sense of risk, and so you back away from the edge without realizing what you're doing or why. "It is not until moments later," continue the authors, "when the person tries to understand his or her behavior, that the individual's slower perceptual system kicks in and potentially misattributes the safety signal ('Getting too close, back up') to a death wish involving heights." (How does one arrive at this particular misreading? Hames and Co., apparently not real big Freudians, venture to blame it on the typical layperson's shaky understanding of psychoanalytic principles—and possibly on the shakiness of the principles themselves.)
All just a big nervous-system misunderstanding, in other words. This is speculative work, but it's an intriguing hypothesis: What seems to be a death wish may not be any sort of wish at all.
Just the same, humor your Uncle Cecil and stay away from those cliffs.
Send questions to Cecil via StraightDope.com or write him c/o Chicago Reader, 350 N. Orleans, Chicago 60654.