Study DesignRetrospective Cohort Study.ObjectivesMental health disorders like depression and psychoses are increasingly recognized in surgical populations and may adversely affect outcomes. This study aimed to: (1) evaluate the prevalence of these disorders among patients undergoing single-level lumbar fusion, (2) compare perioperative complications, costs, and discharge disposition; and (3) determine whether psychotic disorders confer greater risk than depression.MethodsA retrospective study of the National Inpatient Sample (2016-2022) identified adults undergoing elective single-level lumbar fusion procedures. Patients were stratified into depression, psychoses, or control cohorts. Multivariable logistic regression was adjusted for demographic, hospital, and clinical covariates and used to assess associations with perioperative complications, non-home discharge, and inpatient mortality. Hospital costs were converted and inflation-adjusted to 2022 United States (U.S.) dollars.ResultsAmong 792 065 weighted admissions, 17.7% had depression and 2.6% had psychotic disorders. Depression was independently associated with increased odds of cardiovascular complications (OR 1.26), mechanical complications (OR 1.25), adverse events (OR 1.26), and non-home discharge (OR 1.17, all P < .001). Psychotic disorders had greater risk, with higher odds of cardiovascular (OR 1.41), mechanical (OR 1.45), any adverse event (OR 1.42), and non-home discharge (OR 1.59; all P < .001). Mean costs ($41 097 vs $39 256 vs $38,117; P < .001) and length of stay (3.72 vs 3.51 vs 3.19 days; P < .001) were greatest in psychoses.ConclusionDepression and psychotic disorders are common in patients undergoing lumbar fusion, and are independently associated with increases in perioperative morbidity, non-home discharge, and costs. Tailored perioperative planning may help mitigate these risks.