The 35-year-old COVID-19 survivor Leah Blomberg doesn’t remember being rushed to the intensive-care unit, where she would spend 18 days fighting for her life on a ventilator.

What she does remember is far more traumatic.

“I woke up to something that I would never have imagined,” Blomberg told me. A nurse was standing over her hospital bed with a saw, cutting off her arms and legs. Blomberg remembers yelling for help. At one point, she tried to touch her face—and realized, with horror, that only half of her skull was intact.

“I was positive they were trying to kill me,” she said.

Experiences such as Blomberg’s are common among patients in the ICU. The respiratory failure that afflicts the most critically ill COVID-19 patients—acute respiratory distress syndrome (ARDS)—requires mechanical ventilation. Eighty percent of patients on a ventilator suffer from a hallucinogenic state known as ICU delirium, during which they form false, and often frightening, memories. Because these delusional memories are based on real-life stimuli, they’re more vivid than a nightmare—according to Jesse Vanderhoof, they feel “as real as real can get.”

Vanderhoof, who was hospitalized for COVID-19 and spent a week on a ventilator in the ICU, remembers seeing his own death. “I was having these hallucinations where I would be passing out—really slowly falling,” he told me. “I remember specifically having thoughts like, Oh, I’m dying, and this is going to hurt when I hit my face on the ground.” At one point, Vanderhoof saw his own funeral. “It was really traumatic,” he said. “I remember seeing my mom at my funeral.”

Many ICU patients experience delusions related to their deaths, often characterized by harrowing scenarios involving torture or assault. In many ways, this makes sense, Jim Jackson, a psychologist at the ICU Recovery Center at Vanderbilt University Medical Center, told me. While experiencing the acute brain dysfunction of delirium, patients are attempting to create a narrative that reflects the very real pain and stress of their environment. The problem is that the mind transmogrifies reality into something much scarier.

“We’ve had delirious patients who are taken to an imaging center at the hospital to get an MRI,” Jackson told me. “As they are being pushed into the MRI machine—quite appropriately—they’re convinced that they’re being moved into an oven, because that MRI machine bears some vague resemblance in their mind to an oven.” Jackson sees this delusion frequently in his work at the ICU recovery clinic. He also regularly sees patients who misremember a procedure involving a catheter as a sexual assault.

“You can’t tell people, ‘This didn’t happen to you,’” Robert Owens, a pulmonary-critical-care physician at UC San Diego, told me. “That’s what they recall. And so it can be very difficult to treat.”

[ Read: What life is like after being taken off a ventilator ]

While the neuroscientific cause of delirium is poorly understood, its onset is likely due to a concatenation of factors, including hypoxia—oxygen starvation of the brain—and the use of sedatives.

“The muted, sort of restful, peaceful look [of sedated patients] can be mistaken for sleeping when, in fact, their brain is on fire,” said Mayur B. Patel, a trauma physician who researches brain dysfunction and critical illness. (Patel and his team at Vanderbilt University are currently studying deceased ICU patients—including those who died of COVID-19—to learn more about what happened to their brain.)

“We used to think that giving patients sedative medications was protective against longer-term post-traumatic phenomena,” Joe Bienvenu, an associate professor of psychiatry at Johns Hopkins, told me. “But it turns out, if anything, the opposite appears to be the case.”

The recent trend in critical care has been to minimize sedatives as much as possible. Doctors try to avoid benzodiazepines, a class of sedatives that is known to be particularly deliriogenic. But widespread medication shortages have rendered this impossible. On top of that, many COVID-19 patients require prolonged ventilation, which means they need to be sedated for longer, and often more heavily.

The pandemic has forced doctors to abandon nearly all of the evidence-based interventions that can reduce delirium, according to Wes Ely, a professor of pulmonary and critical care at Vanderbilt University Medical Center. As a result, the prevalence of ICU delirium in patients with COVID-19 is sharply rising.

Jackson, who works with Ely, said he’s particularly concerned about the lack of family visitation in ICUs with COVID-19 patients. Multiple studies suggest that attendant family members significantly reduce delirium by providing comfort and tethering the patient to reality.

“Typically, family members help orient these patients to what is factual and what is not,” Jackson told me. “They can say, ‘Honey, trust me, you weren’t actually put into an oven. I went with you to the MRI center. I was there the whole time making sure nothing happened to you.’”

Another strategy that some hospitals employ to mitigate the lasting effects of delirium is the ICU diary. Family members and health-care professionals contribute to a personal journal that details each day the patient spends in the hospital. After patients are discharged, the record helps them reconstruct the narrative of what happened to them.

“Now all those narratives have just been thrown out the window,” Jackson said.

[ Read: After the ICU: What does it mean to be ‘okay’? ]

The absence of family visitation coupled with already overwhelmed medical staff and the extended use of sedatives have many doctors worried about the long-term consequences of ICU stays for COVID-19 survivors. Sounding the alarm the loudest is Ely.

“If you had to design an experiment to make delirium as bad as it could be, COVID is it,” he told me. “COVID is essentially a delirium factory.”

He has reason to be concerned. Delirium is a strong predictor of adverse cognitive, physical, and psychological outcomes for ICU survivors. This cluster of problems that ICU patients can experience post-discharge, called post-intensive-care syndrome (PICS), affects up to 33 percent of all patients on ventilators and 50 percent of patients who stay in the ICU for at least one week. One in four ARDS survivors develops PTSD. That’s a rate similar to that of soldiers returning from combat. Ultimately, a combination of mental-health symptoms and cognitive problems prevents many ARDS survivors from going back to work: Nearly half of the participants in a recent study were unable to return to their previous jobs one year after being discharged from the hospital.

“This is a major public-health problem that most of us don’t even know exists,” Ely said.

Jackson believes that his new COVID-19 patients may fare worse psychologically than other survivors of ARDS. “That dynamic of being terrified of dying, and now in the COVID era, terrified of dying alone—that contributes, we believe, to symptoms of post-traumatic stress disorder,” he told me.

Now that Blomberg’s out of the hospital, she understands that a nurse didn’t actually try to kill her. But that knowledge doesn’t make the memory feel any less real. In addition to struggling with extreme muscle weakness, Blomberg is having trouble sleeping.I’m afraid,” she said, “after the horrible things I saw.”

Another COVID-19 survivor, Fiona Lowenstein, told me she didn’t feel prepared for the onslaught of psychological distress she would experience when she was discharged from the hospital. “I felt bizarre because I was sort of being publicly celebrated by friends, family, and the interviews I was doing for having recovered,” she said. “But I felt like I had this dirty little secret, which was that I was not fully well at all.”

Brittany Lohnes, who survived ARDS in 2016, also felt the dissonance between being celebrated and suffering internally. “Everybody’s like, ‘You’re a miracle. You survived.’ There is absolutely no mental-health follow-up at all,” she told me. Lohnes struggled with flashbacks, anxiety attacks, and major depression for a year until she decided to find a trauma therapist. “Not having any kind of aftercare for the emotional aspect is honestly the hardest part,” she said.

Many ARDS survivors told me that they feel a deep sense of disquiet when COVID-19 patients are discharged from the hospital. Amanda Grow remembers how she was blindsided by the symptoms of PTSD that cropped up nine months after her discharge from the ICU. “They surprised me so much because I thought I was through it,” she told me. First came flashbacks of being intubated—of struggling when two nurses held down her arms to insert a breathing tube. “If you think about a procedure like that, under any other conditions, that would be considered torture,” Grow said. Then came the nightmares. “I just kept having all these nightmares where I was fighting to wake up, fighting to wake up, fighting to wake up,” she said. “I just reached a point where I wished I had died in the hospital.”

Grow was able to seek help for her depression and PTSD. But her recovery involved a long process of acceptance. “We have this perception that people are sick and then they bounce back, but that’s not the way it is at all,” Grow said. “This chapter of your life happens, and it changes every chapter after that. I worry about [COVID-19] survivors experiencing kind of a breakdown of grief, having to go through this reality that their life has changed.”

Like Grow, Peter Gibb, who survived a near-fatal mountain-biking accident, also experienced suicidal thoughts that followed him home from the ICU. “I was lucky enough to be in one of the UK hospitals with an ICU follow-up clinic,” he told me. “You get invited back, and you can talk about what you’ve been through, because there’s a disconnect between the critical phase of your illness and everything you’re feeling.”

Gibb’s long road to recovery inspired him to create ICUsteps, a support group for patients and families who have been affected by critical illness. Knowing the benefits of keeping an ICU diary firsthand, he’s currently developing a cloud-based product that he hopes can be implemented in hospitals with COVID-19 patients across the world.

In the United States, only 16 ICU follow-up clinics serve more than 5 million new ICU survivors each year. Two of the largest clinics—at Vanderbilt and Johns Hopkins—are already seeing an influx of COVID-19 patients.

“Clinicians do such a wonderful job in getting us to the point where we’re going to survive,” Gibb said. “But surviving and getting our life back are two different things.”

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