Introduction

Individual-level determinants of morbidity and mortality have long been recognised as behavioural,1 biological2 and their possible interaction.3 Overarching these are those contextual-level health determinants, which also affect individuals’ morbidity and mortality. These include environmental determinants (eg, access to healthcare resources and reduced exposure to air pollutants),4 alongside less tangible contextual phenomena, such as social integration and cohesion.5 It is argued that effective political and social institutions help create effective government, which in turn provides favourable conditions for a flourishing civil society, with greater social cohesion, high generalised trust and better health.5 6

Generalised trust is an abstract attitude that conceptualises the belief that most people, including strangers, can be trusted. It is considered analytically and conceptually distinct from ‘particularised’ trust, that is, trust in known individuals/groups,7 and ‘political trust’, that is, trust in institutions.6 The foundations of generalised trust are still often debated. Some consider it an unstable attribute, it being the sum of experiences (good or bad) at any given time.8 Others consider that generalised trust is nurtured during one’s formative years, it being stable over the life couse.7 9

That generalised trust and health are positively associated is nothing new. From the field of public health, a plethora of empirical ‘social capital’ research has shown support for the hypothesis that generalised trust (at the individual level and aggregate level) is an independent health determinant.10 However, the relevance of ‘social capital’ has been contested by proponents who highlight the greater importance of public welfare policy and access to material resources for health outcomes.11 Furthermore, there has been debate surrounding the suitability of trust as a social capital proxy.12 13 Despite this, the vast majority of trust and health research comes under the ‘social capital’ umbrella, with associations between morbidity and generalised trust persisting, even in complex analyses.14

Potential mechanisms to how generalised trust equates to better health at the contextual level include that more trusting/cohesive communities maintain greater access to local health services and amenities, reduce ‘deviant health-related behavior’ and levels of violent crime and facilitate the rapid dissemination of positive health messages and behaviours throughout the collective.15 At the individual level, trust is considered to positively influence health by lowering everyday ‘transaction costs’, that is, high generalised trust facilitates collective action, reciprocity and social reinforcement.16 Routinely low transaction costs, therefore, imply reduced psychosocial stresses and anxiety.17 Conversely, low trust/high transaction costs increase social stress and anxiety, which may lead to long-term elevation of blood cortisol levels (due to overstimulation of the hypothalamic-pituitary-adrenal (HPA) axis). Chronically high blood cortisol levels are associated with an increased risk of deleterious diseases, such as type 2 diabetes and cardiovascular disease.17

Empirical evidence of associations between generalised trust and mortality seems sparse and inconsistent in comparison. A recent review by Choi et al 18 found just two studies that employed generalised trust, concluding that there was no significant correlation. Furthermore, a prospective US study concluded that associations initially reported by Kawachi et al 19 between aggregated trust, income inequality and mortality were most likely confounded by ethnicity; however, Deaton and Lubotsky did not include any trust measures themselves.20 Conversely, another US study showed that higher neighbourhood trust was associated with lower neighbourhood total mortality rates after adjusting for socioeconomic status and ethnicity.21 Finally, a cross-national examination of 19 Organisation for Economic Co-operation and Development countries further cast doubt on previously reported positive associations between trust and life expectancy.22

Studies employing individual-level trust and mortality seem restricted to findings from two Nordic countries. First, from Finland, a study of individuals aged 30–79 years found that the negative association between trust and mortality vanished after adjusting for social participation.23 A second study from Southern Finland established an association between men’s (but not women’s) trust and mortality.24 Conversely, a prospective study from Northern Denmark found that trust predicted mortality in women only.25

Of further interest here are those recent discussions around a possible genetic component of generalised trust thought to be shared by specific (inherited) personality traits.26 From the field of health psychology, distrust is the key feature of a character trait known as ‘cynical hostility’.27 Individuals who have cynical, mistrusting outlooks also have a more unhealthy psychosocial risk profile16 17 and a greater risk of mortality.27 28 In trust and mortality research, therefore, a multilevel approach is required to distinguish empirically between individuals who distrust people as part of their pathological personality trait from those who perceive their environment as untrustworthy. Debate surrounding the suitability of trust in social capital research aside,12 no study of trust and all-cause mortality has attempted to disentangle associations between individuals’ generalised trust/distrust and aggregate-level trust (contextual trustworthiness - social cohesion) with general population data. We, therefore, aim to address this shortfall by using a nationally representative sample from US General Social Survey (GSS) data (1978–2010), combined with the National Death Index (NDI) until 2014.