As a nurse, Dunsworth, 45, knew she would require intensive physical rehabilitation. But she wasn’t prepared for the flashbacks. She was drowning, poisoned by nurses, crawling on the floor of a walk-in freezer full of amputated limbs. The images came to her unbidden, memories of events she had never experienced.

Worried that she would be labeled “crazy,” Dunsworth told no one. Eventually, she returned to work. The flashbacks came less frequently, but never disappeared completely.

Last month — nearly a decade after her stay in the intensive care unit — Dunsworth happened upon a study published by investigators from Johns Hopkins University in the journal Psychological Medicine. It described symptoms of post-traumatic stress disorder (PTSD) in survivors of critical care.

“This is my story,” Dunsworth thought.

With new drugs and technologies at their disposal, physicians are becoming better and better at saving lives.

Recently, however, researchers have described a troubling phenomenon: Not only do survivors of the ICU suffer high rates of depression and cognitive dysfunction, but also as many as one in three who are sick enough to require a breathing tube also develop symptoms of post-traumatic stress disorder. While it is more likely to occur in patients with preexisting depression, it can also appear in those without any psychiatric history.

A soldier suffering from PTSD may experience flashbacks of tanks and bombs, terrifying moments of their waking life. In contrast, an ICU survivor may suffer flashbacks of delirium-induced nightmares they had in the hospital, rather than real events. While this is not PTSD as traditionally defined, physicians argue that it is no less debilitating.

“You tend to believe you’re the only one,” says Nancy Andrews, a Maine filmmaker and college professor who suffered symptoms of post-traumatic stress disorder after a lengthy hospitalization in Boston for a life-threatening tear in the wall of the aorta. “You wonder what is wrong with you? You made it out of the hospital, why can’t you get it together?”

The idea that delirious hallucinations could lead to post-traumatic stress disorder is new even for physicians who work in the ICU daily.

Historically, patients were heavily sedated throughout their critical care stay with the dual goals of pain control and amnesia, to prevent patients from having memories of painful breathing tubes, or urinary catheters.

However, research in the past decade has led to a paradigm shift. In 2000, the New England Journal of Medicine published data showing that interrupting sedation daily in intubated patients shortened the amount of time on a breathing tube, and got patients out of the ICU faster. Daily interruptions of sedation, termed “sedation holidays,” became standard.

Fast forward a few years, and physicians now know that delirium itself — the waxing and waning alertness that often afflicts the critically ill who have been sedated — is associated with higher mortality, longer stays in the ICU, and higher costs. These findings have ushered in new practice guidelines, medication changes, and scoring systems to measure patients’ level of delirium.

Against this backdrop comes the somewhat controversial suggestion that patients may leave the ICU to find themselves psychologically devastated. When Christina Jones, a nurse consultant in the United Kingdom, looked to start a post-ICU support group in the late 1990s, she was surprised that the former patients refused to return to the hospital. They met in a local pub instead. Listening to the patients’ stories, Jones said she came to understand why.

“I started to see this pattern of people with flashbacks and nightmares,” said Jones, who pursued a doctorate to study this population more rigorously. “They had very little factual memory, but also had these hallucinations, paranoid delusions of nightmares and alien abductions and nurses trying to kill them. That seemed to be the precipitant for PTSD for a portion of the patients — they couldn’t reject these memories.”