Elon Musk has post-traumatic stress disorder from a turbulent childhood that included time in apartheid South Africa and verbal abuse from his father, famed author Walter Isaacson claims in his new biography of the Tesla CEO.

But does the co-founder of six companies actually have the psychiatric condition, thought to affect around 5% of the global population? Was Isaacson misappropriating the term, as mental health experts say commonly occurs? Or is Elon’s mental state, perhaps, even more nuanced than Isaacson alludes to?

“As a kid growing up in South Africa, Elon Musk knew pain and learned how to survive it,” Isaacson pens in his new book, “Elon Musk,” released on September 12 by publisher Simon & Schuster.

Isaacson—who has authored other best-selling biographies, such as those of Steve Jobs, Jeff Bezos, and Leonardo Da Vinci—writes of young Elon’s time at a South African “wilderness survival camp known as veldskool.” The business savant refers to it as a “paramilitary Lord of the Flies.”

There, “bullying was considered a virtue,” Isaacson writes. “The kids were each given small rations of food and water, and they were allowed—indeed encouraged—to fight over them.” Small and awkward at the time, Elon was “beaten up twice” and lost 10 pounds during his first stint there.

At one point, attendees were “divided into two groups and told to attack each other,” Isaacon writes. “‘It was so insane, mind-blowing,’ Musk recalls. Every few years, one of the kids would die. The counselors would recount such stories as warnings. ‘Don’t be stupid like that dumb f**k who died last year,’ they would say.”

Trauma is common. PTSD isn’t

Such experiences could potentially lead to a diagnosis of PTSD, according to Dr. Craig Chepke, medical director of Excel Psychiatric Associates in Huntersville, N.C., and an assistant professor of psychiatry at State University of New York, who speaks on the topic.

Criteria for diagnosing the condition, according to the Diagnostic and Statistical Manual of Mental Disorders, include “exposure to actual or threatened death, serious injury, or sexual violence.” Because of this, when people think of PTSD, their thoughts often turn to combat veterans or survivors of violent crimes like assault.

“But it really is so much more complicated than that,” Chepke says of the disorder, which could result from intimate partner abuse or even a “significant car accident—anything where there’s any sort of substantial trauma with threat to life or limb, or where there is substantial fear faced.”

Everyone gets scared from time to time. But in the case of fear experienced by those who go on to develop PTSD, “it’s a really dramatically elevated amount,” he tells Fortune. While the fear is appropriate, given the extreme nature of the situation, “the brain kind of learns to remain afraid, so the fight-or-flight response remains persistent long after the threat has been removed.”

But not everyone who experiences trauma will develop the condition, Chepke says. In fact, the vast majority won’t. Why some and not others? Genetics likely play a role, in addition to other factors.

But it’s more than that. “It’s not just that our fate is written in the stars” or in our genes, Chepke says. Adverse childhood experiences—negative, often traumatic events like abuse, neglect, domestic violence, divorce, and parental mental illness, substance abuse, and/or incarceration—can make one more susceptible to developing PTSD. And they can even lead to a different form of the condition.

A more nuanced diagnosis

Aside from traumatic experiences at veldskool and elsewhere, Elon has adverse childhood experiences in spades thanks to his verbally abusive father, Errol, according to the new biography.

The elder Musk “has a Jekyll-and-Hyde nature,” Isaacson writes, citing Elon and his brother, Kimbal. “One minute he would be friendly, the next he could launch into an hour or more of unrelenting abuse. He would end every tirade by telling Elon how pathetic he was.”

The world’s richest man recalls his father’s tirades as “mental torture,” choking up slightly and saying that his father “sure knew how to make anything terrible,” Isaacson pens.

Such abuse doesn’t officially meet diagnostic criteria for PTSD. But it can meet criteria for CPTSD, or complex PTSD, Chepke says. He refers to it as “a different flavor of PTSD”—a mental health condition developed by some who experience chronic or prolonged trauma, or “microtraumas.”

People with complex PTSD “don’t have one specific, defining event, like they were in Fallujah and their buddy stepped on an IED or that type of thing,” the psychiatrist says. Instead, CPTSD involves a series of “less discreetly defined traumas that build up like sediment, that contribute to PTSD—and it’s very real.”

People with the condition often have low self-esteem and relationship difficulties, he says. “They’re very distrustful of others. They become hypervigilant. They assume ill intent of anyone they interact with, because they have no conception of how to truly trust someone.”

Not everyone who has CPTSD realizes they have the condition or even recognizes that they’ve experienced abuse or trauma, Chepke says.

“I can’t tell you, over the years, how many patients, I’ll ask them, ‘Have you ever been abused, neglected, bullied, things like that? And they’ll say, ‘Oh, no. I had a normal childhood,’” he says.

“And then later on it will come out, ‘Well, you know, my dad did beat the shit out of me every night, from the time I was 5 years old until I was 13. But, that’s pretty normal, right?’”

“They genuinely mean it,” he adds. “They don’t have a frame of reference, often. For them, it was normal.”

One, both, neither, or something else entirely

As with PTSD, it’s possible to experience the traumatic events necessary for a CPTSD diagnosis and not develop the condition. Thus, it’s possible that Elon has one or both conditions—or possibly neither, or something else entirely.

Elon’s “PTSD from his childhood … instilled in him an aversion to contentment,” Isaacson writes. But “almost every psychiatric diagnosis is thrown around in popular culture,” Chepke contends.

“Someone who gets good news and is having a good day, and then gets bad news and is having a bad day—someone might say, ‘Oh, they’re so bipolar,’” he says. “Anyone who’s neat and organized, they say, ‘They’re so OCD” (obsessive-compulsive disorder).

The same misuse of terms occurs with PTSD, too, Chepke says. “If someone’s favorite football team loses, they might say, ‘Oh my God, I have PTSD from that game, when the quarterback had five turnovers’ or whatever. Obviously, that’s not PTSD.”

“You can’t assume it’s a verifiable medical diagnosis, just because it’s said.”

One potential case in point: In November, Musk referred to his allegedly having “recession PTSD from keeping X and PayPal alive through the 2000 recession, keeping Tesla alive in the 2009 recession,” Fortune previously reported.

And another: Grimes, the mother of three of Elon’s children, has referred to one of them, named X, having “a three-day PTSD meltdown” when SpaceX’s Starship spacecraft exploded on April 20.

It’s possible, Chepke says, for someone to experience traumatic events and not develop PTSD or CPTSD, but still display behaviors associated with those conditions, like hypervigilance or anxiety.

“They could have major depressive disorder, bipolar disorder, a personality disorder,” he says. “They could have many other completely unrelated psychiatric illnesses that would have occurred, had they never experienced that trauma. There’s overlap.”