Simvastatin for mTBI

Inclusion Criteria: * Males and females ages 21-50 years. * Documented hazardous duty in Iraq and or Afghanistan with the U.S. Armed Forces. * Exposure to one or more blast trauma events resulting in mTBI according to American Congress of Rehabilitation Medicine (ACRM) criteria. * More than 6 months since last blast trauma exposure * Ability to complete psychometric and other clinical assessments in English (i.e., adequate English language skills, vision and hearing). * elevated cholesterol levels, i.e. total cholesterol \>200 and/or LDL \>130. This would generally prompt the initiation of a lipid-lowering agent as standard care in the general medical community. * No use of statins during the previous year and no recent (past 4 weeks) use of other lipid-lowering drugs (e.g., fibrates, niacin \> 500mg/d, or high dose omega-3 fatty acids) preceding randomization. * No clinically significant laboratory abnormalities (electrolytes, glucose, carbon dioxide, blood urea nitrogen (BUN), creatinine, vitamin B12, folate, albumin, thyroid stimulating hormone). * Platelet count \> 100,000/mm2. * Body Mass Index (BMI) between 18 and 36 inclusive Exclusion Criteria: * History of head trauma with loss of consciousness (LOC)\>30 minutes, or with a penetrating head wound, or with moderate to severe memory or other cognitive impairment. * Neurological disorders: multiple sclerosis, epilepsy, stroke, Parkinson's disease (PD), other degenerative Central Nervous System (CNS) disorders, or neuropathy with radicular involvement. * Acute or chronic major psychiatric disorders: schizophrenia, bipolar disorder or severe major depressive disorder, or severe anxiety disorder except PTSD and panic disorder (PTSD and depressive symptoms are common co-morbid conditions for combat mTBI and a subset of these patients have symptoms consistent with panic disorder as well). * Use of illegal drugs; alcohol abuse within the past 6 months. * Poorly controlled hypertension, heart failure, coronary heart disease, peripheral artery disease, carotid artery disease, diabetes mellitus, pulmonary disease with hypoxia or hypercapnia, significant hepatic disease or hepatitis C seropositivity, renal failure, treatment for cancer, HIV positive, active infectious disease or presence of abdominal aortic aneurysm. * Contraindications to lumbar puncture (LP) (e.g., spinal cord injury; deformity, severe disease or infection in the region of the lumbosacral spine; bleeding tendency, use of anticoagulant medications, or platelet count \<100,000/mm2). * Receiving medication in an investigational drug study. * Exclusionary medications (used in the 4 weeks prior to screening): * Fibrates and niacin due to increased risk for myopathy in combination with statins; * Potential drug-drug interactions with statins via effects on CYP3A4: itraconazole, ketoconazole, erythromycin, clarithromycin, HIV protease inhibitors, nefazodone, amiodarone, cyclosporine, isoniazid, quinidine, or large quantities of grapefruit juice (\>1 quart daily); * Selected CNS-acting medications: antipsychotics, anti-Parkinson's disease medications and CNS stimulants * Other medications affecting coagulation and/or inflammation: coumadin, potent anti-inflammatory medications (hydrocortisone, methotrexate or other potent immune-modulating medications), and anti-HIV medications. * All female subjects of childbearing potential will undergo a urine pregnancy test at every subject visit; subjects with positive pregnancy test results will be excluded. In addition, all female subjects of childbearing potential will be required to use a reliable method of contraception throughout the duration of the study.