Background Racism impacts the health and wellbeing of racial minorities across the lifespan. Ethnic-racial identity (ERI) has been suggested as a protective factor against adversity on racial minorities’ wellbeing, however, findings vary between ethnic-racial groups. Research in the Aboriginal Australian context is still limited. The present study tests ERI affirmation as an effect-modifier of the longitudinal association between racism and Aboriginal Australian children’s socio-emotional wellbeing (SEWB). Effect-sizes are hypothesized to be smaller among children with higher ERI affirmation.

Methods Children (n=408) from the K-Cohort of the Longitudinal Study of Indigenous Children (LSIC) were included in the analysis. Data were collected through questionnaire-guided interviews in two time points, when children were 7–10 years and 9–12 years. Children’s racism experience, SEWB (assessed by the Strengths and Difficulties Questionnaire), and confounders were reported by caregivers. Information on ERI affirmation was provided through child self-report. Analyses were conducted in Stata 14. Multiple imputation with chained equations was used to address potential bias due to missing data. Poisson regression with robust errors estimated adjusted Risk Ratios (RRa) for the longitudinal effect of racism on different domains of child SEWB. For the effect-measure modification analysis, RR_a were obtained for the different stratum of the exposure (racism) and the effect-modifier (ERI affirmation). The direction of the modification was indicated by the Relative Excess Risk due to Interaction (RERI) on the additive scale.

Results Children exposed to racism and with low ERI affirmation were at increased risk of increased socio-emotional difficulties, especially for hyperactive behaviour (RRa 2.16, 95% CI 1.00, 4.67), conduct problems (RRa 1.76, 95% CI 0.71, 3.83), and total difficulties (RRa 1.94, 95% CI 0.92, 4.11), although the 95% confidence intervals were wide. Positive effect-measure modification was found in these domains, with respective RERIs of 1.08, 1.39, and 1.14. Contrary to our hypothesis, children with high ERI affirmation were at increased risk of peer problems (RRa 1.80, 95% CI 0.83, 3.90). A negative effect-measure modification was found in this domain (RERI: -0.75).

Conclusion Results indicate that promoting ERI affirmation among Aboriginal Australian children might assist to mitigate the effects of racism on specific domains of child SEWB. Higher effects for peer problems observed for children with higher ERI affirmation suggests the role of ERI among Australian Aboriginal children might differ according to the aspects of ERI and outcomes being considered. ERI could be the target of future interventions in Aboriginal children to offset effects of racism.