Different rates of post-traumatic stress disorder in different countries: Study

A study published in the current issue of Psychotherapy and Psychosomatics provides new insights in the different rates of post-traumatic stress disorder that are found in studies performed in different countries. 

Recent epidemiological studies using consecutive patients have reported inconsistent findings in the prevalence of accident-related PTSD in developed countries. Intercultural differences seem to play an important role in the development of PTSD. Local environmental factors, such as socioeconomic and cultural components, and health care systems are also important. It has also been found an unambiguously positive correlation between income inequality and population health including infant mortality (an indicator of social circumstances and basic population health) at country level. The aim of the present study was to reveal the prevalence of PTSD at 6 months' follow-up in the Authors' prospective study  and to examine the relation between infant mortality rate and prevalence of PTSD in the reliable cross-country data available.

A total of 300 patients consecutively admitted to the intensive care unit (ICU) of a teaching hospital in Tokyo due to accident related injury were enrolled in the study and were assessed shortly after admission and 6 months after their accident. The main outcome measure was the Clinician-Administered PTSD Scale. One hundred and six (35.3%) of the 300 patients completed a face-to-face follow-up interview at 6 months. All patients met the stressor criterion A1. Six patients (5.7%, 95% confidence interval = 1.3-10.1) met all other criteria for accident-related PTSD including A2, and the mean CAPS total score of these 6 patients was 57.8 ±16.1. However, in the present report, the Authors adopted the manner of omitting item 8 (psychogenic amnesia in criterion C) when making the diagnosis of PTSD, because they were often unable to differentiate organic from psychogenic amnesia. 8 (7.5%) patients met criteria for PTSD when item 8 was included in making the diagnosis of PTSD.

The Authors also examined the cross-country relationship between infant mortality rate and prevalence of PTSD. The data from seven studies undertaken in six developed countries (UK, US, Israel, Australia, Switzerland and Japan) as well as the above described data were used. The Authors used data for the prevalence of chronic PTSD (4-12 months after the accident) because spontaneous remission is relatively common within 3 months of a traumatic event. Although self-reported questionnaires are likely to result in elevated PTSD estimates, the investigators used large-scale data from the US and the UK for comparison.

The relation between infant mortality rate and prevalence of accident-related PTSD was nonlinear. On the basis of model fit, the best fitting was obtained with the quadratic model (R 2 = 0.82, p = 0.01), though a linear model was acceptable (R 2 =0.60, p = 0.02). Infant mortality rate is well known to be associated with levels of basic health care, well-developed technology, and medical advances. These rates are also commonly included as part of standard of living evaluations in economics. There are many cultural differences among the six countries such as population density, ethnic background, founding history, dietary habit, and residential setting. The present study showed a plausible explanation for the observed discrepancy in the prevalence of PTSD following injury. These observations may provide clues regarding the estimated prevalence of accident-related PTSD and ways to reduce the number of patients that do develop PTSD. In conclusion, this study gave a concrete sociocultural explanation for the observed discrepancy in the prevalence of PTSD across countries. This explanation may work in terms of preventing PTSD.