Cotard’s patients are seemingly caught in this strange life-death paradox. They believe they know what death feels like. I’ve spent the last half-decade researching and writing on mortality issues, hanging out at death conferences and even enrolling in a college class on death. From simulating near-death experiences to studying the memories of cardiac arrest patients whose hearts stopped beating until they were resuscitated, I’ve often thought about how we challenge the EEG lines that separate death and life because we’re scared of dying. How we live in denial of the finality.

After a neurologist at UCLA told me about Cotard’s patients he studied at the Mexico institute, I boarded a plane from Los Angeles. Turning my 8-month-old over to my husband, I left the cradle of life to explore the ledge of death.

Crumpled in the blue easy chair, Juanita heaves. She is glassy-eyed and skittish. The doctor gently holds her right hand.

Juanita, whose name has been changed to protect her privacy, was admitted to the ward at age 46 and diagnosed with Cotard’s after suffering from a stroke in her temporal lobe, which led to a lesion in her brain. She complained that her limbs had vanished, that her body was defunct and empty like a dummy. She lost the desire to work, eat, live. At times, she was free of the delusion; she recognized her body and her organs, but for much of her waking moments, she was convinced that she was not alive. Now, six years later, this is her 18th visit to the Institute.

Doctors know little about the neurological causes of Cotard’s. Some believe it is not in fact a singular disease, but rather an impermanent condition that is often associated with some combination of encephalitis, Parkinson’s, brain tumors, schizophrenia, depression, bipolar disorder, hypothermia, or brain injuries. Because it’s so atypical, many neurologists and psychologists around the world don’t even think to identify it, or know how.

But the head of this neuropsychiatry unit, Dr. Jesús Ramírez-Bermúdez, might be closer than anyone in figuring out its neurological roots. He has documented and treated more Cotard’s cases at this institute than any other specialist worldwide — a total of 12 — since encountering his first in 2000. To him, studying patients like Juanita is not just about treating them. It’s about trying to understand what is happening in their brains in those moments when they believe they do not exist. “That some people can really experience death in their minds in a delusional way — in a very intense suffering way — has universal value,” he tells me.

Dr. Jesús Ramírez-Bermúdez

What is death, after all, but the dissolution of the self? Beyond the physical feeling of death, if Cotard’s patients have indeed lost their sense of self, understanding why could offer some answers to the most elusive mysteries facing neuroscientists and philosophers: Where does consciousness come from, and how is the self generated?

Juanita is drooling now. She is aware of Dr. Ramírez-Bermúdez, and of me, I think.

“Que paso?” the doctor asks her.

She begins to weep, her chapped, red-rutted face turning a brighter shade, as she trembles.

“Que paso?” he says again.

In an instant, her eyes fill with fury. She looks rabid. Twisting in her seat, she screams in Spanish: “I just want to get the fuck out of here!”

Later, in his office, after leaving Juanita to calm down in her room, Ramírez-Bermúdez sketches a diagram of her brain on a sheet of paper, shading her damaged areas, and pointing out the corresponding areas on the computer, where he has pulled up her neurological scans.

Juanita is one of the most difficult Cotard’s cases he has encountered. She not only suffers from a brain lesion, but has also lived much of her life in a destructive home environment. “My son hates me,” Juanita said during her consultation with Ramírez-Bermúdez. She hits her brother sometimes, and he hits her. “I hate that fucking dog,” she says of him. It’s hard to know how much her home life has contributed to her Cotard’s.

Dr. Jesús Ramírez-Bermúdez draws a picture of the brain.

Ramírez-Bermúdez points to a section of Juanita’s brain on the scan: There is a dark mass on the left side where her lesion lies, affecting the amygdala, which works in concert with the temporal lobes — areas involved in self-awareness, consciousness, and feelings. “Positive emotions produced by the left hemisphere are gone. She cannot produce them, or she has very few,” he says. “Ninety percent of the time she is sad, or angry, or anxious, or fearful.”

Despite Juanita’s erratic behavior, she doesn’t think she’s dead at the moment. For the past three years she has been taking the antipsychotic medication clozapine, which has alleviated her Cotard’s symptoms. But even when Juanita is experiencing a full-blown Cotard’s episode, she still feels emotions. And the most powerful among them might be one of the most human of all: misery.

“They exist in a state of frequent despair,” Ramírez-Bermúdez says of Cotard’s patients. “That’s why they frequently try to commit suicide.”

It’s a maddening quandary to believe you are dead — to know you do not belong on this earth, yet remain here, utterly sad, hopelessly lingering around. Somewhere in the patients’ minds they must realize, if even fleetingly, that they are not actually in-the-ground dead. When they do, Ramírez-Bermúdez explains, it drives some to try to get there. Self-starvation. A blade to the neck. Jumping off a rooftop.

“As a desperate attempt to restore the ability to feel something — anything! — such patients may try to inflict pain on themselves in order to feel more anchored in their bodies,” writes Dr. VS Ramachandran, a neuroscientist at UC San Diego, of Cotard’s patients. If depression had a worst-case scenario, some might consider Cotard’s to be its most dire distant cousin. For many patients, what begins as a state of anxiety, paranoia, fear, like in Juanita’s case, later turns into despondency.

Juanita has an elderly mother, who visits her in the neurology ward often. She is the only stable family presence in Juanita’s life. During each visit, the frail woman sits by her daughter’s side, looking for hints of the person she once was, hoping she will get better.

After spending time with Juanita, I begin to realize that Cotard’s patients are nothing like zombies. Cotard’s patients may have delusions of decay one day and with treatment be rid of them the next. The fact that they can feel at all means they’re trapped in their own living hell.

Patient Rafael Hernández holds his wife, Gisela’s, hand.

Seventy-six-year-old Rafael Hernández hovers at the edge of his dining room, away from his distraught wife, Gisela, who repeatedly wrings her hands and rests them on the plaid tablecloth as she tells me about her husband’s precarious mental state. Rafael has recently been diagnosed with psychotic depression and Cotard’s.

“It is very, very difficult,” she begins. “Not understanding what’s going on. Jesus, when he was crucified, had to walk and he fell. It’s the same process. Falling, standing up. It’s been a long learning process.”

Rafael’s khaki pants and brown cardigan hang off his body. He is hunchbacked, and his mouth sags in a permanent pout. He has not smiled for years. “I’m very afraid. I want to run away now,” he mumbles. “Something is not right, and it’s more than you can imagine.”

We’re sitting inside the couple’s vibrant Mexico City home, which is adorned with collections of intricately painted vases and chinaware, lush plants, and yellow walls. But it’s clear to me that Rafael does not fit in here anymore.

Rafael Hernández

Gisela switches from exasperation to tears, recounting her husband’s cognitive decline. Rafael was once a very different man. Gisela began dating Rafael when she was 15. He loved to debate and was passionate about politics. He always wanted to have the last word. Rafael received a master’s degree in chemical engineering and a doctorate in economics. But 10 years ago, he began to lose interest in his passions. He was no longer active, preferring instead to stay home when she traveled. Last October, Rafael began to speak of feeling like he was not in this world. He complained that his kidneys and organs were obsolete.

“Does your stomach hurt?” Gisela would ask.

He would reply that he did not have a stomach.

“There might be a problem with it,” she said, “but you do have a stomach.”

As Rafael’s illogical behavior continued, he told her he felt spirits all around, and he said things to her like “You are not you. You are a ghost.”

On the Day of the Dead, Mexico’s holiday celebrating loved ones who have passed away, he questioned why his picture was not on the table along with the shrine commemorating the dead. He believed he should have received offerings of food and tequila.

Eventually, he spoke of suicide. After losing 44 pounds in a matter of months, Rafael was hospitalized and put on feeding tubes.

Rafael, his wife, and their daughter.

Rafael listens with his head hanging as his wife speaks about his plight. Gisela takes his hand. Rafael squeezes her hand back. Under the institute’s care, Rafael received electroconvulsive therapy treatments for one month. Such treatments have shown to improve or eliminate symptoms, sometimes curing patients all together.

Rafael improved significantly, Gisela says. But she’s worried that he’s beginning to deteriorate again. Lately, he complains that his teeth do not work, which is why he believes he cannot properly chew or digest food. His doctors say his teeth are fine. He’s having a Cotard’s delusion.

I ask Rafael if he can describe what it’s like to feel dead, and he replies faintly in English: “All my past, all my experience, all my interests, my doctorate degree, my Ph.D. in economics. Now, I am without capacity to remember.”

As with other cases, Rafael’s Cotard’s began with depression, though it would be jumping to conclusions to say that depression is the cause. “Most patients who are severely depressed don’t go around claiming they are dead,” says Dr. Ramachandran. “Something else must be going on.”

Cotard’s syndrome is not listed in the Diagnostic and Statistical Manual of Mental Disorders. The only real way to diagnose it is to conduct psychiatric interviews that must rule out other similar disorders like asomatognosia, a neurological condition that leads to the feeling that one’s body parts are missing.

Ramírez-Bermúdez relies on questioning drawn from the medical literature to diagnose cases, and has determined which specific questions and answers to pay attention to:

“How long have you been a patient?”

Forever. I have always been here. (Indicating, in the Cotard’s patient, that time has stopped flowing, or is moving impossibly slow.)

“Do you know who I am?”

You are no one. You do not exist.

“Who are you?”

I am nothing.

I can’t help wondering: If one doctor reads certain behaviors as delusional depression, psychosis, asomatognosia, or something else, could another call it Cotard’s?

Dr. Ramírez-Bermúdez looks at scans of Juanita’s brain.

Ramírez-Bermúdez has his theories about the roots of Cotard’s. Studying Juanita’s behavior over the years, he found that she scored poorly when asked to identify some colors, animals, fruits, and vegetables. Like patients suffering from semantic dementia, Juanita couldn’t make the right connections. She had trouble on another test, too, one that required explaining or understanding the definition of words like bottle or bowl.

Perhaps a similar network of neural disconnections explains why a Cotard’s patient might not recognize an organ as an organ, or life as a life. Juanita’s brain lesion extends into the anterior temporal lobe — the area that is involved in linking perceptions with actions — which has led to some loss of that semantic memory. Could the delusion of death and problems in semantic processing simply be a rare coincidence? Or could the two conditions be related? Ramírez-Bermúdez wanted to find out.

Two years after encountering Juanita, Ramírez-Bermúdez met a woman who could help solve the puzzle. “Mrs. A,” the 56-year-old patient, had both Cotard’s and semantic dementia, could no longer grasp the word laundry, and could not name items like a pen, shoes, or glasses, or body parts like chin, hair, nose, or knee. Ramírez-Bermúdez, along with UCLA neurologist Mario Mendez, studied the woman, noting that she had been a vegetarian, but could no longer understand the word vegetarian either. She lost the concept of vegetarianism, too, and even began to eat meat.