Incidence and determinants for non-suicidal self-injury in an Italian prison in Milan (Feb-Oct 2023): a retrospective cohort analysis.

Non-suicidal self-injury (NSSI) is a complex and often overlooked public health concern in prison settings, particularly among marginalized populations. This retrospective cohort study investigated the incidence and determinants of NSSI among people living in prison (PLP) at San Vittore, a pre-trial detention facility in Milan, Italy, between February and June 2023. Data were collected and updated until October 1, 2023. Among 712 incarcerated men, 8% engaged in NSSI during their detention. Nearly 90% of all NSSI episodes involved individuals from North Africa. In this subgroup, NSSI was frequently motivated by requests to change cell location or to access medication, underscoring its communicative function within the prison environment. Multivariable analysis showed that, among North African PLP, younger age and a prior history of NSSI were significantly associated with increased risk of self-injury. Among individuals from other regions, psychiatric illness, previous NSSI, and previous suicide attempts were key risk factors, while having children and higher educational attainment were protective. These findings suggest that NSSI reflects not only psychological distress but also structural barriers to care and communication. The study highlights the urgent need for culturally competent, age-sensitive mental health interventions and systemic reforms. Without targeted action, NSSI will remain a critical indicator of unmet needs and health inequities in correctional systems.