Uncertainty Mentalizing and Emotion Dysregulation with Substance Use Severity in Iranian Young Adults; Mediating Role of Borderline Personality Traits

This cross-sectional study aimed was to investigate the mediating role of borderline personality traits in the link between uncertainty mentalizing, emotion dysregulation, and substance use severity among Iranian young adults. The study included 185 substance users aged 18-25 years who completed questionnaires related to the research variables. The results revealed significant direct correlations between all research variables (p < 0.001). Substance use severity was found to be directly influenced by both borderline personality traits (β = 0.19, p < 0.05) and uncertainty mentalizing (β = 0.45, p < 0.001). Furthermore, uncertainty mentalizing was shown to have an indirect effect on substance use severity through borderline personality traits (indirect effect = 0.093, p < 0.05). Uncertainty mentalizing also significantly impacted borderline personality traits (β = 0.49, p < 0.001). However, emotion dysregulation did not demonstrate a significant direct or indirect effect on substance use severity or borderline personality traits. These findings highlight the importance of uncertainty mentalizing as a contributing factor to substance use severity, both directly and through its impact on borderline personality traits. The study suggests that interventions targeting uncertainty mentalizing may be beneficial in preventing and treating substance use and borderline personality traits.