The role of social capital in explaining mental health inequalities between immigrants and Swedish-born: a population-based cross-sectional study

BACKGROUND: Social capital may theoretically explain health inequalities between social groups, but empirical evidence is lacking. Some studies indicate that social capital may be particularly important for immigrant health. Nearly 16% of Sweden’s population are foreign-born immigrants and research has shown them to be susceptible to psychological distress, though significant variation has been found between groups. In this study, we investigate the following hypotheses: 1) if non-refugees have better mental health than Swedish-born, and refugees experience worse mental health than Swedish-born; 2) if mental health status converges with that of Swedish-born with longer duration of residence; and 3) if social capital mediates the effect of immigrant status on psychological distress for different immigrant groups as compared to Swedish-born. METHODS: This cross-sectional study uses baseline data from the Stockholm Public Health Cohort and includes 50,498 randomly-selected individuals from Stockholm County in 2002, 2006, and 2010. Mental health was measured as psychological distress, using the 12-item General Health Questionnaire. Social capital was measured using indicators of bonding, bridging, and linking social capital. Both cognitive and structural aspects were measured for the latter two indicators. Mediation was tested using logistic regression and the Sobel test. RESULTS: The results show that refugees generally had greater odds of psychological distress than non-refugees compared to their respective Swedish-born counterparts. Among immigrant men, both refugees and non-refugees had significantly greater odds of psychological distress than Swedish-born men. Only refugee women in Sweden 10 years or more had significantly greater odds of psychological distress compared to Swedish-born women. The mediation analysis demonstrated that indicators of social capital mediated the association for all immigrant men (except non-refugees in Sweden 3-9 years) and for refugee women in Sweden 10 years or more. While bonding social capital showed the greatest mediatory role among the three social capital types, adding them together had the strongest explanatory effect. CONCLUSIONS: Social capital explains differences in mental health for some immigrant groups, highlighting its role as a potentially important post-migration factor. Increased investment from policy-makers regarding how social capital can be promoted among new arrivals may be important for preventing psychological distress. ELECTRONIC SUPPLEMENTARY MATERIAL: The online version of this article (doi:10.1186/s12889-016-3955-3) contains supplementary material, which is available to authorized users.