Prevalence of post-traumatic stress disorder symptoms in adult critical care survivors: a systematic review and meta-analysis

Mortality in critical care has steadily declined in recent decades [1, 2]. As a result, concerns about long-term outcomes and quality of life in critical care survivors have become a priority. Recently, more attention has been given to the psychiatric consequences of acute illness in the intensive care unit (ICU), especially in young patients. Psychiatric disorders, such as anxiety, depression, and post-traumatic stress disorder (PTSD), are known to have a strong impact on the quality of life in long-term ICU survivors [3].

PTSD is characterized by having been exposed to an event that is life-threatening or perceived as life-threatening and, subsequently, developing intrusive recollections of the event, hyperarousal symptoms, and avoidant behavior related to the traumatic event [4]. Negative changes in cognition and mood are often part of the clinical picture of PTSD. The classical notion of PTSD as a reaction to warfare or natural disasters has been recently extended to include reaction to road traffic accidents, sexual assaults, and medical conditions such as critical care admission [5]. However, the burden of PTSD associated with critical illness remains unclear.

An in-depth understanding of the current prevalence, risk factors, and accuracy of diagnostic tools is essential to establish early interventions aiming to prevent or minimize PTSD after ICU admission [6]. Prevalence estimates of PTSD among ICU survivors have ranged widely from 4 to 62% [7]. This variability seems to be dependent on the time of PTSD assessment, instrument used, and population studied [7].

Although previous systematic reviews of PTSD prevalence among ICU survivors have been published, there has been increasing interest in this topic in the last few years, and the literature on PTSD in survivors of critical illness has expanded substantially. Moreover, there has been an improvement in methods used for pooling prevalence estimates and interpreting their results. Therefore, given the absence of recent reviews on this topic, we designed the present systematic review and meta-analysis to estimate the overall prevalence of PTSD in adult survivors of critical care.

This systematic review and meta-analysis was conducted following the recommendations of the Joanna Briggs Institute (JBI) Reviewers’ Manual [8] and the Preferred Reporting Items for Systematic Reviews and Meta-analyses (PRISMA) Statement [9, 10]. The systematic review protocol was registered with the International Prospective Register of Systematic Reviews (PROSPERO; registration number CRD42017075124).

Of 13,267 records identified, 250 studies were selected for full-text assessment (Fig. 1). Of these, 48 studies enrolling a total of 7152 patients were included in our systematic review and meta-analysis [3, 6, 19‐64].

The characteristics of the included studies are shown in Table 1. The time span of the studies was from 1996 to 2018. Most studies were conducted in mixed ICUs (16 studies), followed by medical ICUs (13 studies), trauma ICUs (5 studies), surgical ICUs (3 studies), and long-term and cardiac ICUs (2 studies each). Ten studies did not report the type of ICU involved. The mean age of enrolled patients ranged from 36.5 to 68.0 years; 27 studies reported a male predominance. Except for 4 studies conducted in Australia [20, 25, 33, 62], 2 conducted in Latin America [24, 29], 1 study conducted in Iran [22], and 4 studies in which location was not reported [30, 41, 46, 57], all other studies (77%) were conducted in the USA or Europe.

In this systematic review and meta-analysis of 48 studies, we found that 1 in every 5 adult survivors of critical care (19.83%) develops PTSD symptoms in the year following ICU discharge. The pooled prevalence of PTSD symptoms in critical care survivors was comparable to that of civilian war survivors (26%) [65], but much higher than that reported in many countries among those exposed to traumatic events (2.5–3.5%) [66]. It was also similar to the 20% prevalence of mental disorder after humanitarian emergencies estimated by the World Health Organization [67]. In the USA, 5.7 million patients are admitted annually to ICUs, with an average mortality rate ranging from 10 to 29% [68]. These data allow us to estimate that approximately 1 million patients develop PTSD after ICU admission annually.

In the present study, the pooled prevalence of PTSD symptoms was 25.69% when measured shortly after ICU discharge (less than 3 months). However, such a high early prevalence of PTSD symptoms may reflect acute stress disorder rather than PTSD. Acute stress symptoms are similar to the post-traumatic stress symptoms that occur within the first month of exposure to a stressor, such as ICU admission [4]. Acute stress disorder may be triggered by fragmented ICU memories of traumatic or psychotic experiences [42] and is a risk factor for the development of PTSD [69]. Although lower, the prevalence range (from 15.93% at 3 months to 18.96% at 12 months) is clinically important, since it may have a negative impact on the quality of life in long-term ICU survivors.

Our systematic review has several limitations. First, despite the use of rigorous, up-to-date methods of data analysis and quality of evidence assessment and a comprehensive search of 6 databases that identified more than 13,000 records, only a few studies reporting data on PTSD prevalence in ICU survivors in specific settings were eligible for inclusion. In addition, most of the included studies had methodological issues that limited the generalizability of the results. Second, PTSD was assessed using different strategies in the included studies. As discussed previously, the diagnosis of PTSD can be challenging, and the use of screening instruments may overestimate PTSD prevalence [70]. However, to date, only a few instruments have been validated for use in the ICU, of which only the Impact of Event Scale—revised [71] and the Post-Traumatic Stress Syndrome 10-Question Inventory have shown good correlation with clinical diagnosis [72]. The lack of proper validation of methods used to evaluate PTSD, as well as their heterogeneity, may have had an impact on the exact prevalence measured in the different studies. However, this impact was minimized in the present systematic review, since similar prevalence estimates of PTSD symptoms were obtained with both clinical assessment (18.58%) and screening instruments (20.18%). Third, there was no parallel assessment of cognitive function in the included studies. An association of long-term PTSD with cognitive dysfunction has been recently reported [73]; however, to date, it remains unknown how cognitive dysfunction can influence PTSD assessment and follow-up, especially regarding consolidation of traumatic memories during mechanical ventilation and sedation. Moreover, PTSD can coexist and be confused with other major psychiatric disorders, such as depression and anxiety [74]. Fourth, the observed statistical heterogeneity was high (90%). However, in contrast with randomized trials, non-controlled studies (e.g., studies of prevalence and incidence) usually have smaller variances and narrower CIs, even with small sample sizes. Thus, a high statistical inconsistency is often expected in meta-analyses of prevalence estimates. Given that the estimates of individual studies included in our meta-analysis ranged mostly from 12 to 30% (similar to the pooled estimate and included in the prediction interval), and we observed consistent results within subgroup analyses (according to instrument used for diagnosis, length of time after ICU stay, and demographic factors), we hypothesize that most of observed inconsistencies may have been the result of the diversity of settings (e.g., patient and ICU characteristics). Fifth, despite the high prevalence observed, it was not possible to establish a direct causal relationship between ICU stay and PTSD, which may be partially explained by other factors, such as the underlying condition of each patient. In this context, action should be taken to further explore the causal relationship between ICU stay and PTSD, as well as to more accurately identify individuals at increased risk of developing PTSD symptoms.

Common stressors in critically ill patients, such as respiratory failure, inflammation, delirium, and communication barriers, may contribute to the occurrence of PTSD, and proper prevention and management of these factors may reduce PTSD incidence after ICU discharge [75]. Also, evidence is emerging that an ICU diary—written by family members or ICU staff—may help patients fill in gaps in their memories, thus reducing the risk of PTSD development [42, 76, 77]. The increased prevalence of PTSD over time in cases that have not received treatment for PTSD symptoms must be highlighted. Although there is little evidence to support the effectiveness of interventions to improve PTSD symptoms among ICU survivors, early treatment with psychotherapy or pharmacological therapy (e.g., antidepressants) may improve quality of life, as observed in PTSD associated with other stressful events [78].

Overall, our findings may have important clinical implications. Despite the high prevalence of PTSD, this disorder is probably underdiagnosed in the post-ICU population. ICU survivors should be screened for PTSD symptoms and cared for accordingly, given the high rates and potential negative impact of PTSD on quality of life. In addition, early and effective measures should be implemented during and after ICU stay to prevent PTSD in this population.

PTSD symptoms affect a large proportion of critical care survivors, with a high expected prevalence in the first year following discharge from the ICU. Screening of ICU patients for PTSD symptoms, followed by proper support and treatment, is needed, given the potential negative impact of PTSD on quality of life. Additional studies should explore whether a causal relationship exists between ICU stay and PTSD, as well as propose additional measures to prevent and treat PTSD among critically ill patients.