Timing of Sexual Debut and Long-Term Psychosocial Consequences: A Causal Inference Approach Using 28-Year Longitudinal Data from Norway

Research examining the association between life course transitions and subjective well-being has largely focused on major milestones such as marriage and parenthood, overlooking other important life events such as first sexual intercourse. In the research focusing on sexual debut timing, the primary emphasis has been placed on early sexual initiation, leaving the psychosocial implications of a late debut largely unexplored. To the best of our knowledge, no prior study has employed a causal inference approach to assess the long-term psychosocial consequences of a late sexual debut. Drawing on a nationally representative cohort study spanning 28 years from adolescence to midlife (n = 1,808), the present study examines the prospective relationship between the timing of sexual debut – early, late, and very late vs normative – and psychosocial well-being in midlife, including mental health (symptoms of depression and anxiety, suicidal ideation), social health (loneliness, social acceptance, social support), well-being (self-esteem, body image, sexual desire), and substance use (tobacco use, problematic alcohol use, drug use). I will apply inverse-probability of treatment weighting (IPTW) to adjust for pre-existing differences in baseline psychosocial well-being, sociodemographic characteristics, and family environment. The study findings will contribute to a deeper understanding of how non-normative sexual debut timing may shape the long-term development of psychosocial well-being.