This study aims to address the critical mental health challenges faced by individuals in prisons and places of detention. By introducing and validating a novel conceptual framework that integrates social determinants of health with the stress process model, this study aims to provide actionable insights for improving mental health care in correctional settings. The research seeks to inform policymakers, prison administrators and mental health professionals about effective interventions and systemic reforms that can reduce recidivism, enhance rehabilitation and promote a more humane and just criminal justice system. This study uses a multi-method research design integrating a systematic literature review, qualitative interviews, multi-criteria evaluation (MCE) and a small-scale empirical study within a correctional facility. The systematic review follows PRISMA guidelines, analysing peer-reviewed articles, government reports and policy documents. Semi-structured interviews with 25 mental health professionals provide practical insights, whereas the MCE assesses intervention effectiveness based on expert consensus. The empirical study involves baseline assessments, intervention implementation and follow-up evaluations using validated tools, providing robust data to validate the proposed conceptual framework that integrates social determinants of health with the stress process model. This study finds that mental health disorders are significantly more prevalent in prison populations than in the general population, with interventions like cognitive behavioural therapy (CBT), peer support programs and trauma-informed care showing considerable effectiveness in reducing symptoms. Emerging technologies such as AI and telemedicine present promising avenues for enhancing care but require careful ethical consideration. The research also highlights the critical role of social determinants and the importance of systemic reforms, such as reducing solitary confinement and integrating prison health care with broader public health systems, in improving inmate mental health and reducing recidivism. This study's quasi-experimental design, while robust, may limit the generalizability of the findings to other correctional settings because of specific facility characteristics. Additionally, the sample size for qualitative interviews, although diverse, could have been larger to provide more nuanced insights, particularly for underrepresented groups. This study highlights the need for more longitudinal research to assess the long-term effects of interventions and the scalability of approaches across different cultural and legal contexts. Future studies should address these limitations by using more diverse sampling, larger sample sizes and extended follow-up periods. This study provides actionable insights for policymakers and prison administrators, emphasizing the need to integrate evidence-based mental health interventions, such as CBT and trauma-informed care, into prison reform strategies. It highlights the importance of training correctional staff in mental health first aid and the potential of emerging technologies like AI and telemedicine to enhance care delivery in resource-limited settings. Implementing these recommendations could significantly improve inmate mental health outcomes, reduce recidivism rates and promote a more humane and effective correctional system, with broader benefits for public health and social equity. Improving mental health care in prisons has significant social implications, particularly in promoting social justice and reducing inequalities. Effective mental health interventions can help break the cycle of incarceration and recidivism, particularly in marginalized communities disproportionately affected by the criminal justice system. By addressing the mental health needs of incarcerated individuals, society can foster safer communities, reduce crime rates and alleviate the economic burden on the criminal justice and health-care systems. Furthermore, enhancing mental health care in prisons reflects a commitment to human dignity, fairness and the rehabilitation of offenders, contributing to a more just and compassionate society. This study introduces a novel conceptual framework that integrates social determinants of health with the stress process model, specifically tailored for correctional facilities. It provides original empirical data from a real-world prison setting, offering new insights into the effectiveness of mental health interventions, such as CBT and trauma-informed care. The study's value lies in its comprehensive approach, combining quantitative and qualitative methods, and its focus on underrepresented populations in correctional settings. By addressing significant gaps in the literature, this research offers practical recommendations for policymakers and practitioners, contributing to improved mental health outcomes and reduced recidivism.