This study found that after adjustment for socio-demographic factors, interpersonal racism is associated with mental but not physical health in a non-U.S. indigenous population. Stress, lack of control and feeling powerless as a reaction to racism emerged in multiple mediation models as significant mediators of the relationship between racism and general mental health.
To our knowledge, this is only the third study to show that racism is associated with general mental health among an indigenous population [35
]. A study among 153 Indigenous Australians found that experiencing regular racism was associated with poor mental health (MCS SF-12) after adjusting for gender, age, education, employment and financial stress, but no association with physical health (PCS SF-12) was evident [35
]. Some previous studies have similarly found that racism is only significantly associated with the mental but not physical health scale of the SF-12/36 [35
] while others identified an association with the physical health scale [39
]. Although the aetiology behind such differences is not yet understood, stronger associations between racism and mental (as opposed to physical) health have been noted worldwide [3
]. As suggested in recent reviews, it is likely that racism impacts primarily on mental health, with physical health effects mediated through mental processes [8
To our knowledge, no previous study has examined the factors included in this study as mediators/moderators of the relationship between racism and physical health. Lack of control is now well-established as a determinant of morbidity and mortality [69
]. Only two previous studies have shown that lack of control acts as a mediator of the association between racism and mental health (see below) while control beliefs failed to emerge as a mediator between racism and depression in another study [71
]. In a study involving 108 Arab-Americans, lack of control completely mediated the association between racism and self-esteem, and partially mediated the association between racism and psychological distress [72
]. Similarly, mastery (i.e. the opposite of lack of control) mediated the relationship between racism and psychological distress among 485 African-American, Native-American and Asian-Americans [73
]. Racism may lead to lack of control by creating unfair and unpredictable demands as well as attenuating rewards resulting from effort, with one study finding that increased reporting of racism among Latino students was associated with lack of control [74
]. In one previous study of racism and health among Indigenous Australians, mastery failed to emerge as a significant mediator [40
]. To our knowledge, this is the first study to suggest that lack of control may act as an effect modifier between discrimination and poor mental health, with discrimination only affecting only those low in control.
Eleven studies have examined social support, connections or capital as a mediator/moderator of the association between racism and mental health, with some evidence that it ameliorates the detrimental effect of racism on health [5
]. This study, however, is the first to examine the role of negative social connections, finding it to be a significant mediator (but not moderator) of the relationship between racism and poor health when considered alone in a single variable mediator model.
It is possible that racism perpetrated by friends or relatives may take the form of demands, arguments, criticism, being let down or annoyance. Alternatively, or in addition, racism-related stress may precipitate negative social connections or reduce the capacity of individuals to tolerate social connections (hence increasing the reporting of negative connections). This latter possibility is supported by a study which found racism to be associated with increased reporting of routine social interactions as harassing, exclusionary, and unfair [76
]. The failure of this mediator to emerge in the multiple mediation model suggests that it may act as a second-order mediator in a causal pathway with stress as the primary mediator.
Although two previous studies have found that improved mental health outcomes are associated with active rather than passive coping responses to racism [77
], none of the six responses to racism mediated the association between racism and mental health in the DRUID study. However, powerlessness as a reaction to racism was found to be a significant mediator. This finding is particularly disturbing given that among a nationally representative group of Indigenous Australians, almost a third (28%) reported feeling powerlessness as a reaction to racism [34
]. Somatic reaction was significant in single variable mediation models but was no longer so in the multiple mediation model. Although no previous research has examined reactions as mediators of the relationship between racism and ill-health, a study involving 183 Indigenous Australians found that racism which evoked an emotional/physical response was related to poor general health [39
A previous study involving 215 multiethnic college students found that optimism was inversely associated with depression in a model that also included perceived racism [79
]. However, this construct failed to emerge as a statistically significant mediator between racism and mental health in the DRUID study. Given that no other studies have specifically focused on optimism as a mediator, it is not yet clear how this construct may contribute to the aetiology of racism as a determinant of health.
Reviews in this field suggest that stress acts as a mediator between racism and poor health [3
]. However, only a few studies have examined such a role, with stress acting as mediator between racism and: smoking [21
], depression/anxiety [80
], hypertension [82
] and psychological well-being [75
] while failing to emerge as a mediator between racism and depression [83
]. Both acute and chronic stress emerged as important mediators in this study, remaining significant in multiple mediation models (with the exception of chronic stress in the interpersonal racism model). This supports the view that racism acts (at least in part) as a form of stress that, in turn, leads to both physical and mental ill-health through various psychological and physical consequences (e.g. allostatic load) [84
Although four studies have found that ethnic identity buffers racism-related stress [75
], a recent review of 12 studies notes that identity is not sufficient to completely ameliorate the effects of racism on health [87
]. It is not clear why the two aspects of cultural identity assessed in this study failed to emerge as either significant mediators or moderators of the association between racism and mental health.
Results from models with interpersonal racism and discrimination-related stress were largely consistent, providing confidence that findings were not spurious. There were, however, some differences in findings across these two independent variables. In particular, discrimination-related stress was only associated with poor mental health among participants reporting a lack of control in life while no moderation was detected for interpersonal racism. While four significant mediators emerged in common across these two variables in single-mediation models, lack of control and negative social connections mediated only in models with interpersonal racism while somatic reactions mediated only in the model with discrimination-related stress as the independent variable. In multiple mediation models, acute stress was significant in both models. Lack of control was only significant in interpersonal racism model while powerlessness and chronic stress were significant in the discrimination-related stress model.
Variations in findings across the two measures of exposure may be related to the fact that discrimination-related stress assessed experiences not specifically attributed to race/ethnicity. Previous studies have found that association with health can vary across different measures of discrimination [88
]. Further work is required to understand the nature and implications of these differential associations. Differences may also be due to the fact that discrimination-related stress also included assessment of vicarious as well as personal experiences of racism (i.e. racism experienced by family/friends). Although research on vicarious racism is very limited [3
], there is some evidence of its detrimental effects on health and wellbeing [40
The robustness of study findings is supported by broadly similar findings for both interpersonal racism and discrimination-related stress. Nonetheless, there are several study limitations to note. First, in terms of measurement, it is evident that racism can go unnoticed when it does occur and be perceived when it is not 'objectively' present (i.e. an avoidable and unfair inequality of resources, opportunity or benefit has not, in fact occurred). However, as with stress, perceived racism may act as a determinant of health regardless of its objective veracity [3
The MIRE captures only those experiences of racism that respondents perceive and are willing to report. There is evidence that respondents are more likely to underestimate than overestimate experiences of racism [91
]. This is due to a combination of factors, including the poorly understood (and largely invisible) nature of systemic racism, the protective effects that may accrue from not attributing experiences to racism [95
], and the negative social repercussions of labelling an experience as racism [94
Although 32 longitudinal studies suggest that the primary direction of causation is from racism to ill-health rather than ill-health leading to increased reporting of racism [3
], the latter cannot be ruled out in this cross-sectional study.
Failure to identify any significant moderators may have been due to the low power of moderation tests [99
] combined with a relatively small sample size. Similarly, low power due to both the small sample size and the need to dichotomise mediators may have precluded identification of weaker mediation effects [100
With figures ranging from 0.60-0.80 in the literature [101
], there is no established cut-off for satisfactory reliability as measured by Cronbach's alpha. Nonetheless, it is clear that two of the composite measures in this study had low to moderate internal consistencies (acute stress: α = 0.66 and optimism: α = 0.58). As such, these scales may have not have tapped into their respective underlying constructs with sufficient accuracy. While the optimism scale (LOT-R) has well established internal consistency [103
], the acute stress scale is novel to DRUID and its psychometric properties should be examined in further research.