Background Social capital has been extensively studied as one of the determinants of population health including mental health over the past 20 years. There is existing evidence linking depressive disorders with CVD mortality and all-cause mortality in many countries including Russia. However, research exploring determinants of mental health in Russia including social capital is limited.

Methods We assessed relationships between social capital and mental health in a large cross-sectional study, the International Project on Cardiovascular Disease in Russia (IPCDR), based in two Russian cities: Arkhangelsk and Novosibirsk. The study used a random sample of 5051 people aged 35–69. The collected data included measures of socio-economic status and demographic variables: age, sex, education, perceived financial situation, and marital status.

Mental health measures Having any depressive or anxiety disorder were defined as ≥10 score calculated from the Patient Health Questionnaire (PHQ-9) and Generalized Anxiety Disorder 7 (GAD-7) scales.

Social capital measures We used three questions to measure social capital with 11-point scale answer options: 1) Social mistrust, ‘Generally speaking, would you say that most people can be trusted, or that you can’t be too careful in dealing with people?’; 2) Perceived lack of fairness: ‘Do you think that most people would try to take advantage of you if they got the chance, or would they try to be fair?’; and 3) Perceived unhelpfulness: ‘Would you say that most of the time people try to be helpful or that they are mostly looking out for themselves’. The scales were dichotomised 0/6-low social capital and 7/10-high social capital and each was used as a separate dependent variable in analysis.

Statistical analysis We employed two logistic regression models to assess associations between social capital and mental health, 1) adjusting for age, sex and city, 2) adjusting for age, sex, city, marital status, education level and self-reported financial situation.

Results All three measures of social capital were associated with depression and anxiety after adjusting for socio-economic and demographic variables: ‘Social mistrust’: OR 1.49 (95% CI, 1.14 to 1.94), ‘Perceived lack of fairness’: OR 1.75 (95% CI, 1.39 to 2.20), ‘Perceived unhelpfulness’ OR 1.72 (95% CI, 1.36 to 2.17) for depressive disorder; ‘Social mistrust’: OR 1.40 (95% CI, 0.99 to 1.99), ‘Perceived lack of fairness’: OR 2.37 (95% CI, 1.71 to 3.29), and ‘Perceived unhelpfulness’: OR 2.19 (95% CI, 1.57 to 3.04) for anxiety disorder.

Conclusion Our findings from Russia support previous research showing the relationships between social capital and mental health. Further investigations on direction of the effect and pathways explaining these associations are needed.