The role of post-traumatic stress disorder and depression in predicting disability after injury

Injury is a leading global cause of morbidity and mortality.1 Each year over 350 000 Australians experience an injury severe enough to warrant hospital admission.2 The aim of trauma health care services is to restore damaged body structures and functions, and to prevent or limit disability (defined as the difficulty an individual has performing activities and roles within the context of his or her environment3). The determinants of long-term disability are often complex, involving interaction between physical, psychological and social factors. Elucidating early markers of later disability provides an opportunity to identify at-risk patients, with the potential to modify treatment approaches to improve long-term function.

New episodes of psychiatric disorder occur in 10%–20% of patients after injury sufficiently serious to require hospitalisation.4 Post-traumatic stress disorder (PTSD) and depression are among the main psychiatric disorders to develop after injury.5 Although the rates of post-traumatic mental health problems after injury are relatively low (about 10% for PTSD), the high frequency with which injury occurs renders it a leading cause of post-traumatic mental health disorders.6

Disability after injury is strongly but not exclusively determined by characteristics of the injury. A body of literature has also shown a relationship between exposure to traumatic stressors (independent of injury) and poor physical health and functioning.7 After injury, anxiety and depression contribute to lower levels of return to work and poorer quality of life.8

The degree to which PTSD and depression affect disability, relative to characteristics of the injury, has not been well described. In light of this, we conducted a large, multisite longitudinal study to examine the role of post-traumatic mental health on long-term disability following traumatic injury. Importantly, we sought to investigate the independent contributions that PTSD and depression made to later disability by controlling for demographic variables (sex, age, employment status, marital status), pre-injury disability, and characteristics of the injury (severity, intensive care unit admission, length of hospital stay, mild traumatic brain injury [MTBI], discharge destination).

Participants were recruited from four hospitals in three states of Australia (Alfred and Royal Melbourne Hospitals in Victoria, Westmead Hospital in New South Wales, and Queen Elizabeth Hospital in South Australia). A random sample of patients admitted to trauma services on weekdays were recruited to the study over 23 months, from 13 March 2004 to 21 February 2006. We used an automated, random selection procedure, stratified by length of stay. Random selection was used rather than a consecutive design because the numbers of patients admitted to each trauma service was far greater than recruitment resources allowed.

Patients were included in the study if they had experienced a traumatic injury that required a hospital admission of longer than 24 hours; were aged 16–70 years; and had sufficient English comprehension to complete the assessment. Those with an MTBI (defined as a loss of consciousness of 30 minutes or less, or a Glasgow Coma Scale score of 13–15 after 30 minutes, or post-traumatic amnesia not longer than 24 hours9) were included in the study. Patients were excluded if they had moderate to severe traumatic brain injury, were suicidal or had psychosis.

The study procedures were fully explained to the patients who met our inclusion criteria and whose written informed consent was obtained. Initial assessments were conducted, on average, 7.2 days (SD, 9.6 days) after the initial admission for injury. The assessment consisted of a structured clinical interview that assessed the presence of PTSD or subsyndromal PTSD, and self-report questionnaires that assessed demographics, pre-injury disability, pre-injury alcohol use and acute depression. Injury-related information was derived from automated hospital-based registry systems. At 3 and 12 months, we used a structured clinical telephone interview to assess PTSD or subsyndromal PTSD. Participants were also sent self-report questionnaires at 3 and 12 months to assess current depression and disability, and returned them in reply-paid envelopes.

The study was approved by the human research ethics committee at each hospital, and at the University of Melbourne.

Of the 1593 patients randomly selected for the study, 1047 (66%) consented to participate and completed the initial assessment; 904 participants (86%) completed the 3-month assessment, and 802 (77%) completed the 12-month assessment.

Of those who completed the 12-month assessment (and adjusting for missing variable data), 573 (72%) were male, with an average age of 39 years (SD, 13.7). Half of the sample who completed the 12-month assessment (367; 50%) were married or in a de-facto relationship, and 68 (10%) were not employed. Sixty-two per cent of patients (448) had more than high-school education. Forty-four per cent of participants (342) experienced an MTBI, and the mean ISS was 11.4 (SD, 8.4), which is in the moderate range of severity. Participants spent an average of 12.4 days (SD, 12.3 days) in hospital, and 16% of participants (120) had an ICU admission.

Transport crashes were the principal mechanism of injury (518 participants; 65%); 131 participants (17%) had falls, 51 (6%) were assaulted, 38 (5%) had work-related accidents not specified in the above categories, and 55 (7%) were injured in other ways. Most participants were discharged home (605; 78%), and the remainder were discharged to a rehabilitation facility.

Individuals who refused to participate in our study did not differ from those who participated in terms of sex (χ2 = 1.50; df, 1; non-significant), length of hospital admission (t[1571] = 0.92; non-significant), or ISS (t[1561] = 1.46; non-significant). Those who refused to participate were younger than participants (t[1433]) = 3.44; P = 0.001).

Individuals who failed to complete the 12-month assessment did not differ from those who completed it in terms of sex, days in hospital, or presence of an MTBI. Those who did not complete the 12-month assessment were younger (35.3 ± 13.1 v 39.0 ± 13.7 years; t[1143] = 4.4; P < 0.001) and had a lower ISS (10.2 ± 7.3 v 11.4 ± 8.4; t[676.5] = 2.4; P = 0.02).

A total of 18% of patients (144) fell into the 12-month high-disability group. Box 1 shows the between-group differences across all measured variables.

All variables (demographic, injury characteristics, pre-injury disability and alcohol use, and initial mental health characteristics) were entered into a logistic regression. PTSD (including subsyndromal PTSD) at 1 week significantly predicted high 12-month disability (AOR, 2.37; 95% CI, 1.28–4.41; P = 0.006), as did high levels of depression (AOR, 1.87; 95% CI, 1.11–3.16; P = 0.02). In the second logistic regression (Box 2), after controlling for all variables, 3-month PTSD (including subsyndromal PTSD) significantly predicted 12-month disability (AOR, 3.67; 95% CI, 2.02–6.67; P < 0.001), as did 3-month depression (AOR, 3.36; 95% CI, 1.85–6.11; P < 0.001).

Our prospective study demonstrates the relationship between early mental health problems after injury and later disability. Specifically, PTSD/subsyndromal PTSD and depression in the first 3 months after injury significantly increased the risk of disability at 12 months, independent of other variables including pre-injury disability and injury severity. The finding that 3-month PTSD and depression predicted disability after controlling for 1-week symptoms suggests that PTSD and depression symptoms escalate over the first 3 months after injury, and it is this escalation of symptoms that is particularly associated with disability. PTSD and depression each made a unique contribution to later disability, despite often being comorbid. Our findings suggest these two diagnoses contribute to later disability in different ways.

The relationship between injury, early PTSD and depression, and later disability has important implications for the care of injured patients. Clinicians being aware of the potential comorbidity between physical ill health and mental health problems could improve the care of injured patients. Providing information,21 empathic listening,22 and maintaining continuity of care23 may all improve the patient’s experience of feeling supported. Feeling supported after a traumatic event is associated with decreased adverse psychological sequelae.24 Likewise, acknowledging common stressors, such as uncertainty about recovery, ongoing physical symptoms, and financial pressures, is likely to improve patients’ satisfaction with care.

Injured patients can be screened in the initial stage of their hospital admission to identify those who are at higher risk of developing mental health problems. Several screening tests are available for this purpose, including one specifically designed for identifying risk of PTSD and depression in injured patients.25 Once patients are identified as being at high risk, they should receive regular follow-up through primary care, with early referral to mental health services if symptoms emerge or escalate. Early psychological interventions show promising results in preventing and/or treating post-traumatic mental health problems.4

In lieu of, or perhaps in addition to, early screening, injured patients with high levels of disability should be screened for current mental health problems. Short screens such as the HADS for anxiety and depression, or the PTSD Checklist26 are suited to this task. If mental health problems are identified, specialist assessment leading to trauma-focused cognitive behaviour therapy is the first-line treatment for PTSD,27 and cognitive behaviour therapy and/or antidepressant medications are effective for major depression.28

This study is limited in a number of ways. First, the 12-item WHODAS II assessed premorbid disability retrospectively, and there may have been an interaction between being injured and reporting of prior disability. Second, the main mechanism of injury in this sample was motor vehicle accidents, with only a small proportion of patients experiencing assault. How well these findings generalise to other countries where interpersonal violence makes up a larger proportion of injury to patients is unknown, given that interpersonal violence is associated with higher levels of PTSD than other mechanisms of injury.29 Similarly, because we selected weekday admissions, patients who were admitted and discharged on the weekend were not a part of this sample. They might represent a different group to the whole sample. Finally, there may be limitations to generalising these findings to young people, given that younger people were less likely to participate in the study and less likely to complete the 12-month assessment. We can only speculate why young, less severely injured participants were less likely to complete the study, but, anecdotally, we found that these young participants had reengaged in their lives and were “too busy” to complete the questionnaires.

Our finding that early psychological distress predicts disability at 1 year represents both a challenge and an opportunity. The challenge is to develop treatment models that acknowledge the close interaction between physical and psychological factors, in contrast to the fragmented discipline-specific approach currently taken. The opportunity is that, in doing so in the immediate aftermath of injury, long-term disability may be reduced.