Overall, our findings revealed a significant predictive effect of value orientation on PTSD prevalence in a sample of 11 European countries. In particular, low crime rates and high modern value orientation (i.e., aggregate factor) predicted higher PTSD prevalence. This result was supported by the model that substituted “stimulation” for the aggregate factor as representative of modern value orientation, which excluded the possibility of co-dependency of values within the aggregate factor. In this model, the main effect and interaction effect of stimulation accounted for the highest variance in PTSD prevalence, compared with the individual value “conformity”, as representative of traditional values.

Whilst much research effort has been invested in identifying and analysing the relationship of numerous biological and psychological factors and their interplay with PTSD, the variability of PTSD prevalence in relation to diverse cultural and societal influences has so far been under researched. To fill this gap, the aim of the current study was to explore these potential societal influences, including historical and cultural factors, using value orientations. Supported by findings from previous research by our group, we hypothesised that disparities in PTSD prevalence across European countries are related to differences in value orientations and in trauma exposure rates [6, 7].

Our main finding showed a strong association between war fatalities and PTSD prevalence rates across the 11 European countries included in this study. This association remained stable in subsequent multivariate analyses, even after including value orientations. For most countries, the war death rates taken as a proxy for trauma exposure were based on WWII victims. A number of previous studies have shown that affected people still suffer from PTSD or present with severe PTSD symptoms 60 years post WWII (the original studies on PTSD in the different countries were conducted between 1998 and 2005). Living through WWII and its aftermath involved being confronted with a number of distressing life situations, such as direct personal exposure to combat or bombings, traumatic experiences during migration or displacement, or more ‘indirect’ effects resulting from consequential childhood hardships (such as starvation, cold, migration, or displacement), which can be triggered by subsequent traumatic events into full-blown PTSD [33]. The latter effect is known and discussed as a secondary or tertiary traumatisation effect [34].

With regard to aggregate or individual value orientations, correlational findings between number of war victims and value orientation essentially confirm previous study findings that reported modern values, especially stimulation, were positively associated with PTSD and even more so with trauma exposure rates [6, 7]. Stimulation, as a modern value orientation, is distinguished by seeking excitement, novelty, and challenge in life, by daring and by living a varied and exciting life. In our study, the expression of this value was stronger in nations who reported a higher number of traumatic events and increased PTSD rates. To the best of our knowledge, no social-psychological or sociological explanation exists for this association between population-level value orientation and PTSD prevalence. However, on an individual level, the relationship between trauma exposure and/or PTSD and the personality trait of “sensation seeking” has been debated and substantiated for its pathological effect [35, 36]. Sensation seeking describes an urge to pursue novel, intense and complex sensations and experiences, and the willingness to take risks for the sake of such experience. As such, it is comparable to the population-level value of “stimulation”. Research evidence has suggested an association between sensation seeking and PTSD, although not in the direction previously predicted from the compulsive exposure hypothesis (i.e., high sensation seeking is associated with PTSD). In a study conducted by Joseph et al., the investigators explored the association between PTSD and impulsivity (parameterised as consisting of the two components impulsiveness and venturesomeness). The authors found no relationship between PTSD and venturesomeness, but a significant association between PTSD and impulsiveness [36].

Further interesting results were observed related to the other exposure types, crime, natural disasters, and road fatalities, investigated in this study. Crime and road fatality related trauma exposure and PTSD was predicted not only by the exposure rates themselves but also by the cascades of main and interaction effects of value orientation x trauma exposure. For the trauma proxy of crime victims, a modern value orientation in society predicted the development of PTSD. When taking the interaction effect between modern values and trauma exposure into account, an additional increase in PTSD rates was observed. In terms of the modern value “stimulation”, this means that higher stimulation values predicted higher PTSD. This association was strengthened when including the interaction effect between stimulation and trauma exposure (i.e., crime rates). The latter may be particularly true in countries such as Bulgaria or Rumania, which have low rates of officially reported crimes (which formed the basis for our data analyses), but a much higher true figure of crimes [37]. A tentatively significant, but reverse, finding was found for road fatalities, in which stimulation as a modern value predicted lower PTSD rates, and in which lower crime exposure combined with lower stimulation values predicted higher PTSD. The UK, the Netherlands and Germany showed comparably low rates of road fatalities, and citizens with low modern stimulation orientation were consistently more prone to develop PTSD when exposed to road accidents, compared with citizens with traditional value orientations (e.g., conformity).

To interpret the differential findings described in the preceding two paragraphs, a simple distinction may help: war and crime-related victimisation belong to the category of interpersonal traumatic exposure. These traumas are considered to be especially anomalous and aberrant by the victims, who subsequently look for culprits and perceive the world as meaningless and incomprehensible, and consequently change their world-views [38]. In contrast, accidental trauma, such as natural disasters or road fatalities, is perceived as inevitable and predestined, and provokes fear and caution [39]. Because of this, interpersonal trauma is more likely to negatively interact with modern values, such as stimulation, compared with accidental trauma that will correlate positively. In other words, individuals living in countries where modern value orientations predominate are more likely to suffer traumatic stress due to interpersonal trauma exposure, whereas in countries with traditional value orientations, accidental or coincidental trauma might lead to substantial stress.

When interpreting the influence of cultural values on trauma and trauma consequences, additional aspects such as whether and how trauma exposure itself might shape cultural orientation need to be considered. Research on changes in pro-social attitudes after traumatic events, e.g., natural disasters [40] and terroristic attacks [41], does suggest such effects. Furthermore, our results suggest that the effects of traumatic events can last more than 40 years, further highlighting the potential intergenerational effect of trauma sequelae, and how such stress-related consequences can be present in offspring of war combat participants [42].

Importantly, the results of this study need to be interpreted in view of certain study limitations. First, because information on value orientation and corresponding PTSD prevalence was not available for all European countries, resulting in 12 countries included in this study, restricted power in statistical testing needs to be addressed. To address this issue, statistical methods were chosen that are proven to be highly satisfactory when sample sizes are small. Nevertheless, replication of the study in other populations with information available on war victimisation (in particular, World War II) and other civil traumas, as well as on PTSD prevalence and value orientations, should be considered.

Second, the high PTSD prevalence in some of the countries included in this study might not result from war deaths alone but also from recent war survivors, e.g., British and French soldiers that were involved in the Gulf War, where most likely other soldiers from other countries were not involved. Although this heterogeneity in sample characteristics of war victimisation might have contributed to variation in PTSD figures, we highlight the fact that several other sources of traumatisation (road fatalities, natural catastrophes and crime victimisation) were included in the study; thus, allowing for a comprehensive understanding of population traumatisation and value orientations, and their associations with PTSD.

Third, the fact that the primary determinants included in this study are estimates originating from various sources that have been jointly investigated in these secondary analyses should be considered. Although all sources are valid and representative, and estimates (or so called proxies of trauma exposure) have been assessed using solid methodologies, the unknown error variance of each parameter needs to be considered when interpreting the results. Furthermore, aggregate data have a high risk of misinterpretation as often described by “Simpsons Paradoxon”. It describes a case of probability statistics in which a trend that appears in different groups of data disappears when these groups are combined, and the reverse trend appears for the aggregate data. This result is often encountered in social science and medical science statistics and is particularly confounding when frequency data are unduly given causal interpretations. Therefore, replication of the results in other population using study-specific, non-aggregated data is needed.