Scottish administrative data tracking all 2015 prison releases reveals formerly incarcerated individuals access mental health and substance use services at dramatically elevated rates compared to demographically matched community controls. The study linked healthcare records for over 8,000 released prisoners against 40,000 general population comparisons, finding 4-fold higher rates of mental health service contacts and 6-fold increases in substance use treatment engagement following release. This represents the most comprehensive population-level analysis of post-incarceration healthcare utilization patterns to date. The findings illuminate a critical transition period where released prisoners face compounding health vulnerabilities while navigating fragmented care systems. Previous research has established high mortality rates in the weeks following prison release, but this study provides granular insight into the healthcare pathway preceding adverse outcomes. The data suggests current reentry support systems inadequately address the mental health burden carried by this population. For policymakers, these utilization patterns argue for proactive mental health interventions beginning before release rather than reactive emergency responses. The scale of service demand also indicates substantial healthcare cost implications, as emergency and crisis interventions are far more expensive than preventive care models. This evidence base could inform targeted investments in prison-to-community transition programs focused on mental health continuity.