A stay in hospital intensive care unit could put patients at unique risk of having psychiatric troubles such as depression or post-traumatic stress disorder, according to a study by researchers at Columbia University’s Mailman School of Public Health and colleagues at University of Pittsburgh, Ohio State University, and Denmark’s Aarhus University Hospital. A large percentage of the critically ill population had no history of diagnoses such as depression or treatment for depression yet had substantially increased rates of this diagnosis and prescriptions for psychoactive medications in the year after the critical illness. However, the largest increase in risk occurred in the first few months after the critical illness, suggesting that the risk may be temporary. Findings are published online in the Journal of the American Medical Association.

“In the community of providers of critical care, there is an increasing awareness that this is a likely issue for people after intensive care,” said Dr. Hannah Wunsch, assistant professor of epidemiology and anesthesiology at the Mailman School of Public Health. “However, there had not been good population level research on this issue before.”

The investigators analyzed data from Denmark’s National Registry of Patients, one of the most comprehensive repositories of patient information because all of that country’s hospitals are included. They looked at 24,179 intensive care patients who had been admitted to a hospital between 2006-2008 with an “unanticipated critical illness” and had received mechanical ventilation. They compared this group of patients to two other groups: general population controls and a population of patients who stayed in a hospital but were not critically ill. The intensive care cohort was at a 20-fold increased likelihood of receiving a new psychiatric diagnosis or psychoactive medication compared to the general population in the first few months after critical illness, and at a 2-3 fold increased risk compared with the non-critical care hospital population.

However, the absolute risk of receiving a new psychiatric diagnosis in the first three months after being discharged was small. The results are consistent with smaller cohort studies, some of which were done in the U.S., according to Dr. Wunsch. The instances of post-intensive care psychiatric diagnosis could even be higher in the U.S. because overall rates of diagnoses of psychiatric illnesses are higher here than in Western European countries.

There are no standards for screening for depression, anxiety, and PTSD when discharging patients, according to Dr. Wunsch, who practices in the surgical intensive care unit at Columbia University Medical Center. “We certainly see patients who by the end of their stay in intensive care are severely depressed,” she says. She has also met patients months or years after their stay in an ICU who say they have PTSD from the experience.

The study was supported by the Danish Medical Research Council, the Clinical Institute at Aarhus University, and the Department of Clinical Epidemiology’s Research Foundation at Aarhus University Hospital.