Linda Dietrich

Abstract Background Borderline personality disorder (BPD) is a severe mental illness associated with emotional and functional impairment, elevated suicide risk, and high individual and societal costs. BPD is under-researched in the general population, especially among males, and from a developmental perspective. We examined the prevalence and development of BPD symptoms in young men and explored the longitudinal associations with risk-taking behaviors. Methods Data came from the prospective-longitudinal Cohort Study on Substance Use Risk Factors (C-SURF), a population sample of young men. Participants were screened for BPD risk using the McLean Screening Instrument (MSI-BPD) at mean age 25 (2016–2018; n = 5,516) and again at mean age 28 (2019–2020; n = 5,367). Risk-taking behaviors (e.g., interpersonal violence, gambling, substance use) were self-reported at both time points. Multilevel regression models examined within-person changes in BPD symptoms, including self-harm, and risk-taking behaviors over time. Results 7.4% of participants had a high risk of BPD, defined by endorsing 7 + MSI-BPD items at least once. Among those with 7 + items endorsed at the first assessment, 29.5% still endorsed 7 + items three years later. Despite a general within-person decline in BPD symptoms with age, participants at initially high risk for BPD continued to exhibit elevated levels of risk-taking behaviors after three years. Conclusion BPD symptomatology affects a substantial proportion of young men. Despite its modest stability over time, it is associated with persistent engagement in various risk-taking behaviors. Interventions targeting BPD symptoms in male populations may offer a promising avenue towards mitigating substantial psychosocial burden associated with these behaviors.