Depression and substance use are common co-occurring conditions. Sometimes depression has been found to be the precursor of substance use. The aim of this study is to find out the relationship between levels of Depression and Substance Use among students of tertiary institutions in Taita Taveta County, Kenya. In this study, two theories will be used to explain the variables; Wendy Treynor’s Depression Theory (2009). The study shall focus on depression levels and its relationship with substance use. The study will use a correlational research design. All the respondents from the four participating tertiary institutions shall be assessed using both Beck’s Depression Inventory (BDI) and the Alcohol, Smoking and Substance Involvement Screening Test (ASSIST)
