Today, many patients survive a critical illness due to advances in medicine, yet such experience exposes them to both stress and pain. Past studies have suggested that as a result some patients may develop a range of psychiatric disorders, including post-traumatic stress disorder, anxiety, and depression. A new study conducted in Denmark found that patients who survive critical illness may have an increased risk of being diagnosed with a psychiatric illness. Yet the opposite was true as well — mental illness may also predispose patients to critical illness.

“Our study provides key information extending findings from several small studies of intensive care survivors that observed a high prevalence of varying psychiatric disorders after hospital discharge,” wrote the authors in a summary of their research appearing online in JAMA. “Of note, there appeared to be an increased prevalence of psychiatric diagnoses and prescriptions for psychoactive medication among patients receiving mechanical ventilation relative to control groups in the year prior to the critical illness.”

A complete understanding of the potential links between psychiatric illness prior to critical illness as well as the possibility of an increased risk of mental illness following hospitalization has eluded scientists for some time. To assess the psychiatric implications both before and after serious illness, a team of researchers led by Dr. Hannah Wunsch of Columbia University conducted a population-based study in Denmark of patients found to be critically ill in the years between 2006 and 2008 (with follow-up through 2009). The study also included two matched comparison cohorts, one of hospitalized patients and one of the general population. For the purposes of the study, the researchers defined critical illness as intensive care unit (ICU) admission with mechanical ventilation. They also defined psychiatric prescription drugs as those that affect mental functioning, including mood, behavior, or thinking processes.

What did the team discover? Among the 24,179 critically ill patients, 6.2 percent had one or more psychiatric diagnoses in the five years before entering the ICU as compared to 5.4 percent among hospitalized patients and just 2.4 percent among the general population. The proportion of critically ill patients with preadmission prescriptions for psychoactive drugs during the five-year period before ICU amounted to 48.7 percent, a figure that was similar to the already hospitalized (48.8 percent) yet considerably higher than the general population (33.2 percent).

Among the 9,921 critical illness survivors with no previous psychiatric history, the risk of a new psychiatric diagnosis in the first three months following ICU admission was relatively low, but still higher than that of hospitalized patients (0.5 percent versus 0.2 percent ) and higher than that of the general population (0.02 percent). The number of patients given new prescriptions for psychiatric drugs also increased in the first three months following ICU admission — 12.7 percent versus 5.0 percent for the hospital group and 0.7 percent for the general population. These differences, though, had largely resolved by the end of the first year of follow-up.

“Prior psychiatric diagnoses are more common in critically ill patients than in hospital and general population cohorts,” the authors concluded. “Among survivors of critical illness, new psychiatric diagnoses and psychoactive medication use is increased in the months after discharge.” Seemingly, the overall psychological impact of severe illness felt by most critically ill patients is slight and primarily transient. It's still very much worth it to survive.

Source: Wunsch H, Christiansen CF, Johansen MB, Olsen M, Ali N, Angus DC, Sørensen HT. Psychiatric Diagnoses and Psychoactive Medication Use Among Nonsurgical Critically Ill Patients Receiving Mechanical Ventilation. JAMA. 2014.