Objective: Trust in institutions such as the government is lower in the context of mental health problems and socio-economic disadvantage. However, the roles of structural inequality, interpersonal factors, and mental health on institutional trust remain unclear. This study aimed to examine the associations of social and mental health factors, from early life to adulthood, with institutional trust. Method: Participants (n=1347; 57.2% female) were from the population-based Quebec Longitudinal Study of Child Development (1997-2021). Trust in 13 institutions was self-reported at age 23. Predictors were 20 social and mental health factors during early life, adolescence, and adulthood. Associations were examined with linear regressions corrected for false discovery rate. Pathways were explored using the temporal Peter-Clark algorithm. Results: Early-life factors associated with lower levels of trust were male sex, racialized minority status, low household income, and maternal history of depression and antisocial behaviors. After adjusting for early-life factors, adolescence factors associated with lower levels of trust were internalizing and externalizing problems, bullying exposure, and school difficulties. Independently of early-life or adolescence factors, adulthood factors associated with lower levels of trust were perceived stress, psychotic experiences, suicidal ideas, and seeking professional help, whereas greater social capital was associated with greater trust. Temporal Peter-Clark analyses identified social capital and psychotic experiences as potential proximal determinants of institutional trust. Conclusion: This study identified factors associated with institutional trust reflecting an interplay between structural inequality, interpersonal relationships, and mental health over development. Interventions aimed at promoting social inclusion may improve institutional trust and population wellbeing.