Background: Androgen deprivation therapy (ADT) increases the risk of developing depression which can affect quality of life and adherence to treatment. Depression has been associated to inflammation in patients with cancer. Albumin and neutrophil-to-lymphocyte ratio (NLR) are inflammatory biomarkers that to our knowledge have not been evaluated in hormone mediated depression in prostate cancer (PC). The aim of this study is to evaluate the severity of hormone related depression and its association with inflammatory biomarkers, demographics, and cancer treatment variables and to determine antidepressant treatment response. Methods: A retrospective chart review of consecutive referrals to psycho-oncology of PC patients on ADT with new onset depression was conducted. Demographics, cancer and psychiatric history, and laboratories within 1 week of initial visit were collected. Assessments for depression included clinical interview and patient-rated scale [Beck Depression Inventory (BDI)]. These measures were done at baseline (before starting an antidepressant) and follow-up to determine treatment response. Successful antidepressant treatment response is defined as ≥50% reduction in baseline BDI score. Statistical analysis comparing the association of clinical variables between depression, inflammatory biomarkers, and demographics included Pearson’s correlation, chi-square, ANOVA, t-test, and binary logistic regression was used to determine associations with depression. Data was dichotomized using median split for inflammatory biomarkers due to skewness. Results: A sample of 26 PC patients on leuprolide (mean age 70 years; 13 Hispanic, 13 non-Hispanic) included 13 with mild depression (BDI£20) and 13 with moderate- to-severe depression (BDI>20). Moderate-to-severe depression was associated with higher NLR (≥3, p= .041), stage IV PC (n=15, p= .001), and Hispanics (p= .033). Lower albumin (£3.9) was associated with higher age (p= .007), higher NLR (p= .006), and non-Hispanics (p= .049) but not depression. Over 54% (13/24) of patients did not respond to antidepressant treatment. In logistic regression only NLR and Stage IV PC remained significantly associated with depression after adjusting for confounding variables. Conclusions: NLR and stage IV PC were both associated with moderate-to-severe depression. These results are likely due to increased level of inflammation in advanced cancer. Inflammation has been associated with treatment resistant depression which could explain why 54% of patients did not respond to antidepressant treatment. NLR is an inexpensive routinely used test in cancer centers that has the potential to be used as a biomarker of severity of depression in PC patients.