Fax +41 61 306 12 34 E-Mail karger@karger.ch www.karger.com Letter to the Editor 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 in- terval = 1.3–10.1) met all other criteria for accident-related PTSD including A2, and the mean ( 8SD) CAPS total score of these 6 patients was 57.8 8 16.1. However, in the present report, we adopted the manner of omitting item 8 (psychogenic amnesia in criterion C) when making the diagnosis of PTSD [15], because we were often unable to differentiate organic from psychogenic am- nesia. For reference purposes, 8 (7.5%) patients met criteria for PTSD when item 8 was included in making the diagnosis of PTSD. We examined the cross-country relationship between infant mortality rate and prevalence of PTSD. Methodologies which in- cluded the consecutive recruitment of accidentally injured pa- tients in emergency departments or intensive care units, prospec- tive design, and assessment according to internationally accepted diagnostic criteria suggest the validity and comparability of these data. Studies were excluded if they included help-seeking patients, patients recruited from police records, or all patients with trau- matic brain injury. The data from seven studies undertaken in six developed countries (UK, US, Israel, Australia, Switzerland and Japan) [2–8] as well as our current data were used. We used data for the prevalence of chronic PTSD (4–12 months after the acci- dent) because spontaneous remission is relatively common within 3 months of a traumatic event. Although self-reported question- naires are likely to result in elevated PTSD estimates, we used large-scale data from the US and the UK [2, 3] for comparison. The infant mortality rates in each country for the year when each study was conducted or submitted to the journal were used [16]. The relation between infant mortality rate and prevalence of accident-related PTSD was nonlinear ( fig. 1). 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 associ- ated 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 popu- lation density, ethnic background, founding history, dietary hab- it, 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 re- garding the estimated prevalence of accident-related PTSD and ways to reduce the number of patients that do develop PTSD. The present Japanese study has methodological strengths, in- cluding consecutive sampling and standardized assessment. However, we also consider important limitations related to repre- sentativeness, such as sampling from only one hospital and a rel- atively high dropout rate. Furthermore, a higher prevalence of Not only has accidental injury been shown to account for a significant health burden on all populations, regardless of age, sex and geographic region [1], it is also an important risk factor for posttraumatic stress disorder (PTSD). Recent epidemiological studies using consecutive patients have reported inconsistent findings in the prevalence of accident-related PTSD in developed countries. For instance, PTSD prevalence at 4–12 months after accident was in the range of 17–32% in the UK [2], US [3] and Is- rael [4], but at considerably lower rates of 10.4% in Australia [5], 8.5% in Japan [6], and 1.9–3.1% in Switzerland [7, 8]. In a recent study by Schnyder et al. [8] published in Psychotherapy and Psy- chosomatics, the authors discussed that intercultural differences play an important role in the development of PTSD. We agree with their suggestion that local environmental factors, such as socio- economic and cultural components, and health care systems are also important. In this context, Babones [9] showed an unam- biguously positive correlation between income inequality and population health including infant mortality (an indicator of so- cial 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 our prospective study [10] and to exam- ine 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 short- ly after admission and 6 months after their accident. The main outcome measure was the Clinician-Administered PTSD Scale [11, 12]. The method and sociodemographic and clinical informa- tion have been presented in an earlier publication [10]. Briefly, the majority of participants were men (77.7%), the average ( 8SD) age was 36.5 8 15.0 years, the average ( 8SD) Injury Severity Score [13] was 9.1 8 7.9, and the median Glasgow Coma Scale score [14] was 15.0 (range 3–15). Published online: November 18, 2009 © 2009 S. Karger AG, Basel 0033–3190/10/0791–0056$26.00/0 Accessible online at: www.karger.com/pps Psychother Psychosom 2010;79:56–57 DOI: 10.1159/000259418 Towards an Explanation of Inconsistent Rates of Posttraumatic Stress Disorder across Different Countries: Infant Mortality Rate as a Marker of Social Circumstances and Basic Population Health Yutaka Matsuoka a, b, c , Daisuke Nishi a, b, c , Naohiro Yonemoto a, c , Satomi Nakajima a, c , Yoshiharu Kim a, c a National Institute of Mental Health, National Center of Neurology and Psychiatry, b Department of Psychiatry, National Disaster Medical Center, and c CREST, Japan Science and Technology Agency, Tokyo, Japan