This retrospective observational study at an Academic Brain Injury Center included participants evaluated 3–12 months post-TBI with available IGF-1 values and complete Rivermead Post-Concussion Symptoms Questionnaire (RPQ-13), Generalized Anxiety Disorder-7 (GAD-7), and Patient Health Questionnaire-9 (PHQ-9) responses. The gene discussed is IGF1; the disease is brain injury.