To evaluate the risk of developing a new mental disorder diagnosis within two years of lower extremity fracture. Design: Retrospective cohort study. National insurance claims database. Included were patients between the ages of 18 and 65 with lower extremity, pelvis and acetabular fractures without prior mental disorders as defined with ICD-9 and ICD-10 diagnosis codes. Mental disorders evaluated included alcohol use disorder, generalized anxiety disorder, bipolar disorder, major depressive disorder, drug use disorder, panic disorder, post-traumatic stress disorder, and suicide attempt.Outcome Measures and Comparisons: The individual lower extremity fracture cohorts were matched 1:4 with non-fracture controls. The specific groups of interest were pelvis fractures, acetabulum fractures, proximal femur fractures, femoral shaft fractures, distal femur fractures, patella fractures, tibia plateau fractures, tibia shaft fractures, ankle fractures, pilon fractures, calcaneus fractures, and Lisfranc fractures. Rates of mental disorders after primary lower extremity fractures within two years were compared using multivariable logistic regression. Overall, the 263,988 patient fracture group was 57.2% female with an average age of 46.6 years. Compared to controls with no fracture, patients who sustained pelvis, acetabulum, proximal femur, femoral shaft, distal femur, patella, tibia plateau, tibia shaft, pilon, calcaneus, or Lisfranc fracture had a statistically significant increased risk of being diagnosed with a queried mental disorder within two years of fracture. When comparing all fracture patients by location, those suffering from fractures proximal to the knee joint, including pelvis fractures (OR: 1.51, 95% CI: 1.39-1.64) and proximal femur fractures (OR: 1.36, 95% CI: 1.26-1.47), demonstrated greater risk of developing any of the queried mental disorders compared fractures distal to the knee, including ankle fractures (OR: 0.99, 95% CI: 0.95-1.03) and pilon fractures (OR: 1.05, 95% CI: 0.81-1.36). When comparing specific fracture patients to patients without fracture by mental disorder, patients demonstrated an increased risk of suicide attempt following fracture of the pelvis, acetabulum, femoral shaft, distal femur, and calcaneus, as well as patients suffering a Lisfranc fracture. There is an increased risk of being diagnosed with a new mental disorder following lower extremity trauma in patients without prior mental disorder diagnosis compared to matched individuals without a lower extremity fracture. Among the fractures studied, those that were more proximal, such as pelvis and proximal femur fractures, carried the greatest risk compared to more distal fracture sites, including ankle and pilon fractures. Patients who experienced certain lower extremity fractures had a significantly higher rate of suicide attempt compared to patients without fracture. Physicians should consider increased mental health screening and potential referral for mental health evaluation for patients following lower extremity trauma. Prognostic Level III. See Instructions for Authors for a complete description of levels of evidence.