Pediatric medical traumatic stress (PMTS) has been defined as “a set of psychological and physiological responses of children and their families to pain, injury, serious illness, medical procedures, and invasive or frightening treatment experiences”.1 It refers to a continuum of trauma symptoms (e.g., arousal, re-experiencing, avoidance) which may be present without meeting criteria for a full diagnosis of PTSD or ASD2, and which may contribute to later mental health difficulties, such as anxiety and depression. Currently, little is known about the long term mental health outcomes of pediatric surgical patients, particularly when surgery is more invasive. The purpose of this project will be to use existing administrative data to compare the mental health outcomes of pediatric patients who received more invasive surgical procedures (e.g., required hospitalization) as compared to less invasive surgical procedures (e.g., outpatient care only) with matched controls between the years of 1981 and 1991. We will compare the mental health outcomes of these groups over time, including clinical diagnoses of depression or anxiety and psychotropic drug prescriptions. We hypothesize that children who experienced more invasive surgeries will also experience more mental health difficulties in adulthood than children who experienced less invasive surgeries or matched controls. The role of the BSc Med student will be to learn how to apply for permission to access the administrative data, code and analyze the data, review the scientific literature and summarize the results.