Over 5% of Americans over the age of 12 reported depression between 2005–2006, and it remains the second leading cause of death in the adolescent and the early adulthood population. The estimated worldwide impact of depression affects approximately 300 million people (World Health Organization [WHO], 2017). Few research studies analyzed the correlation of depression and postoperative pain. The impact of depression on physiological wellbeing, and evidence from various studies suggest a correlation between psychological illnesses such as depression and the physiological manifestations of pain. This systematic review will consider Randomized Controlled Trials (RCT’s), however in the absence of RCT’s, a Quasi-experimental design, and Prospective cohort studies, will be included. Inclusion criteria for the systematic review consists of: adults ≥ 18 years of age with self-reported depression, subjects who have mild, moderate, or severe postoperative pain, subjects who received anesthesia or analgesia, and who underwent ambulatory surgery. Six of the nine studies reported higher postoperative pain levels among participants who had increased preoperative depression, and three out nine studies reported a negative correlation. Overall limitations in this review include the inability to obtain the highest level of evidence such as RCT’s. Due to lack of available RCT studies, cohort studies provided the primary basis of information for which this study relied. Cohort studies do not provide the highest level of evidence, and therefore an increased level of heterogenicity within this study was apparent.