Background: Limited research exists regarding the influence of preoperative depression on postoperative mental health, physical function, and pain in lumbar decompression (LD) patients. This study aims to evaluate the association of depressive symptoms as measured by the Patient Health Questionnaire-9 (PHQ-9) with other mental health and physical function clinical outcomes among patients undergoing LD.Methods: A prospectively maintained surgical registry was reviewed for primary LD from March 2016 to May 2019. Patients were stratified into 3 preoperative PHQ-9 score subgroups. Higher PHQ-9 scores indicated greater depressive symptoms. We assessed demographic and perioperative characteristics among subgroups with appropriate statistical testing. We also evaluated outcome instruments and postoperative improvement for the following outcomes: PHQ-9, Short Form 12 (SF-12), Veterans RAND 12-Item (VR-12), Patient-Reported Outcomes Measurement Information System Physical Function (PROMIS-PF), visual analog scale (VAS) leg, and VAS back.Results: The 351-subject cohort was 70.4% men with an average age of 47 years; 186 subjects had minimal preoperative depressive symptoms (PHQ-9 <5), 94 had moderate (5≤ PHQ-9 ≤10), and 71 had severe (PHQ-9 >10). Subgroups with more severe symptoms of depression had worse mental health outcome scores , and VR-12-MCS) and a positive linear association with greater pre-to postoperative mental health improvements at all timepoints. Subgroups with more severe symptoms of depression had worse PROMIS-PF scores at all timepoints, though VAS pain scores had no depression symptom association by 1 year.Conclusion: Patients with more severe preoperative depressive symptoms, as evaluated by PHQ-9, have a greater improvement in PHQ-9, SF-12, and VR-12 scores, but more severe PHQ-9 scores are associated with worse overall physical function scores. This study demonstrates the relevance of preoperative depressive symptoms and their necessity in future risk factor models.Level of Evidence: 3. Clinical Relevance: Severity of preoperative PHQ-9 acts as a significant risk factor to postoperative pain and mental and physical health improvement.