Biopsychosocial vulnerability and parental behaviors, attitudes, beliefs, and well-being in first-time mothers and fathers: A nationwide Canadian longitudinal study.

= 2,787) across Canada self-reported various biopsychosocial vulnerabilities (e.g., lower couple relationship quality, lower perceived social support) at a single time point, with most factors collected at 3 weeks postpartum and others at 3 months postpartum. Parents further reported on parental outcomes (e.g., involvement, distress, overreactivity) starting at 3 months postpartum for up to five time points across the first 2 years postpartum. Results showed that vulnerability factors had the strongest and most frequent associations with initial status in parental outcomes, with lower relationship quality and lower perceived social support having the largest effect sizes. These patterns were similar for both mothers and fathers. In contrast, the number and strength of associations with change in parental outcomes over time was smaller. While lower relationship quality and perceived social support were linked to improvements in some parental outcomes over time, high childhood adversity, immigrant background, lower household income, and lower education were associated with less favorable changes in outcomes. These patterns varied between mothers and fathers. Overall, the findings underscore the contribution of biopsychosocial vulnerability in the functioning and well-being of first-time parents, with shared and unique risks for mothers and fathers. (PsycInfo Database Record (c) 2026 APA, all rights reserved).