This assessment is designed to develop your research, critical review of evidence and writing skills to support health advocacy in the domain of Public Health; The assignment will reflect on policy content relevant to the population health issue and critical analysis of evidence-based research to inform your practice.In this assignment, you will select a vulnerable population group (people living with mental illness and Substance use Disorder (SUD) comorbidity, Australian Indigenous peoples, adults with depression or Post Traumatic Stress Disorder & youth (15-24), specifically on the prevalence of comorbidity or co-occurring mental health and AOD disorders or misuse as discussed in this topic. The report will investigate social, environmental, interpersonal and economic factors which are known to influence the development of mental and co-occurring SUD and problems. The report will link to current Australian policy approaches to prevention, treatment or support for the chosen population group which address the risks or protective factors identified.