DC WRIISC's Staff - War Related Illness and Injury Study Center
Attention A T users. To access the menus on this page please perform the following steps. 1. Please switch auto forms mode to off. 2. Hit enter to expand a main menu option (Health, Benefits, etc). 3. To enter and activate the submenu links, hit the down arrow. You will now be able to tab or arrow up or down through the submenu options to access/activate the submenu links.

War Related Illness and Injury Study Center


Quick Links

Veterans Crisis Line Badge
My healthevet badge


Our staff consists of physicians, nurse practitioners, physician assistants, psychologists, research scientists, epidemiologists, complementary and alternative medicine practitioners, and environmental health scientists who have many years of experience seeing veterans with post-deployment health concerns. Below is a description of the clinical and research backgrounds of our current DC WRIISC staff members:


Matthew J. Reinhard, PsyD
  • Position: WRIISC Director

Dr. Reinhard is the Director of DC WRIISC. He has been with the WRIISC-DC since 2008 as a clinical neuropsychologist and has seen many Veterans with a variety of post-deployment health concerns. He obtained his BA from Long Island University, his MA and PsyD from Pepperdine University (APA), and interned at the Kaiser Permanente Los Angeles Medical Center (APA). He completed a two-year post-doctoral fellowship in neuropsychology at the University of California-Los Angeles (UCLA), Semel Institute for Neuroscience and Human Behavior. He has recently published neuropsychology research the areas of: PTSD, Complementary and Integrative (CIM) Approaches.   He has also worked as a clinical psychologist in the PTSD treatment program at the Washington DC VAMC. His current area of research interest is brain behavior relationships in PTSD, Gulf War Illness, and CIM. He has an academic appointment at the Associate Professor rank from Georgetown University Medical School Department of Psychiatry.

Contact Dr. Reinhard at: 202-745-8249.

< back to top

John P. Barrett, MD, MPH, MS, FAAFP, FACPM
  • Position: Deputy Director

Dr. John Barrett joined the War Related Illness and Injury Study Center in November 2019 after retiring from the Army with over 30 years of service at the rank of Colonel. He most recently served at the Uniformed Services University of the Health Sciences where he was the Army Senior Service Leader and the Deputy Director of the Division of Epidemiology and Biostatistics. Dr. Barrett began his military service after high school, enlisting as an Army medic. He then attended the University of California, Davis, serving as a National Guard flight medic, and commissioning as a Second Lieutenant through Army ROTC. He received his medical degree from the Uniformed Services University of the Health Sciences, and later attended the University of Washington, receiving a Master of Public Health in Health Education and a Master of Science in Health Services. As an Army Medical Corps officer, Dr. Barrett has served in several leadership, teaching, and clinical positions in the U.S. and abroad. He is a Fellow of the American Academy of Family Physicians and the American College of Preventive Medicine and is board certified in Family Medicine, Preventive Medicine, Occupational & Environmental Medicine, and Aerospace Medicine. His academic interests include population health, military occupational and environmental exposures, clinical health services, lifestyle medicine and brain health, and leadership in healthcare. Dr. Barrett’s military awards include the Army Surgeon General “A” Designation and the Order of Military Medical Merit.  

Contact Dr. Barrett at (202) 745-8249.

< back to top

Nate Allen, BS
  • Position: Grant Manager

Mr. Allen, BS, is a Research Grant Manager at DC WRIISC and graduate of Trinity College, CT. He is currently a research coordinator and primary investigator for WRIISC studies including inhibitory reflex control via eye movements, integrative and alternative medicine for Gulf War Veterans, and the intersection of health and mobile technologies. He hopes WRIISC’s interdisciplinary work with multi-symptom illnesses, TBI, and PTSD will contribute to positive health outcomes for future Veterans.

Contact Mr. Allen at: 202-745-8000, ext. 55474.

< back to top

Charity B. Breneman, PhD, MSPH
  • Position: Senior Exercise Physiologist

Dr. Breneman is an Exercise Physiologist with the DC WRIISC. She graduated from Brigham Young University with a BS and MS in Exercise Science. She went on to earn a PhD in Exercise Science with an emphasis in health aspects of physical activity and a MSPH in Epidemiology from the University of South Carolina (USC). Dr. Breneman also completed a postdoctoral fellowship in health services research at the Rural and Minority Health Research Center at USC. Her current area of research includes examining the bidirectional relationship between exercise and sleep, the acute and chronic effects of exercise on post-deployment health, and the individualization of exercise training prescriptions.

Contact Dr. Breneman at: 202-745-8000, ext. 55823

< back to top

Ryan C. Brewster, PhD
  • Position: Clinical Neuropsychologist

Dr. Brewster is a Clinical Neuropsychologist and Neuropsychology Fellowship Director at the WRIISC-DC.  He obtained an undergraduate degree from the University of Miami and a PhD in Clinical Psychology through the joint Clinical Psychology and Neuropsychology and Cognitive Neuroscience programs at Georgia State University. Dr. Brewster then completed a clinical internship in Adult Neuropsychology at the University of California-Los Angeles (UCLA) Semel Institute for Neuroscience and Human Behavior and a two-year post-doctoral fellowship in Clinical Neuropsychology specializing in Traumatic Brain Injury/Rehabilitation at the West Los Angeles VAMC.  His clinical responsibilities include conducting neuropsychological assessments of Veterans with a wide range of complex neurocognitive and emotional concerns.  His current research interests are in the combined application of neuroimaging and neuropsychological assessment to better understand TBI and epilepsy, cognitive rehabilitation following TBI, and disentangling overlapping cognitive and emotional symptoms common in mTBI and PTSD.

Contact Dr. Brewster at: 202-745-8000, ext. 56800

< back to top

Jeremy Chester, BS
  • Position: Data Manager

Mr. Chester, BS, is a Data Manager at DC WRIISC. He has a BS in Biochemistry from Binghamton University. He has worked for the Department of Veterans Affairs since 2016, and he previously served in the United States Marine Corps Reserves for six years, including a one-year active duty deployment in support of Operation Iraqi Freedom. He has conducted research on a variety of topics, including the genetic basis of thyrotoxicosis, the media’s portrayal of Chronic Multi-Symptom Illness, treatments for Gulf War Illness, and the history of translational research in Gulf War Illness. He has published research on thyroid hormone receptor disease. He is currently involved in several research studies with the WRIISC, including treatments for Insomnia in Gulf War Veterans, identifying biomarkers, the course of illness, and targeted treatment approaches for Gulf War Illness, and clinical outcomes of Mefloquine use. He is involved in clinical operations at the WRIISC, including database queries and management and a value stream analysis of clinical operations. He also is involved in WRIISC educational operations, including development of an educational module on depleted uranium exposure and a remote health coaching project.

Contact Mr. Chester at: 202-745-8000, ext. 55769

< back to top

Timothy Chun, BS
  • Position: Health Science Specialist

Mr. Chun, BS is a research assistant at the DC WRIISC. He received his bachelor’s degree in Community Health at the University of Maryland, College Park. He has a background in electroencephalogram (EEG) research and will continue this research at WRIISC. Mr. Chun looks forward to expanding his experience in research and to assist the WRIISC team to achieve their goals.

Contact Mr. Chun at 202-745-8000, ext. 55818

< back to top

Michelle E. Costanzo, PhD
  • Position: WRIISC DC Research Director

Dr. Costanzo is the Research Director at the DC WRIISC and has a faculty position as a Research Assistant Professor of Medicine at the Uniformed Services University of the Health Sciences (USUHS). She has over 15 years of human subjects research experience with 8 years experience specifically focused in a military research environment (Department of Defense and Veterans Affairs). She has a strong publication history related to post-deployment health topics and expert populations such as elite athletes and physicians, including the 2017 Military Medicine Article of the Year for her work as lead author of the article "Psychophysiological Investigation of Combat Veterans with Subthreshold Post-traumatic Stress Disorder Symptoms."  Specifically, her military-relevant research has utilized psychophysiology and neuroimaging to examine post-traumatic stress disorder and mild traumatic brain injury during fear conditioning, combat-related virtual reality, affective stroop, and telemedicine to reveal insight into the etiology of persistent symptoms associated with deployment. Her recent interest has focused on behavioral interventions aimed at augmenting cognitive control and executive functioning based on neuroscientific understanding of stress, brain structural and functional plasticity that could help Veterans achieve the self-regulation competence to enable them to master patient-driven healthcare. She holds a BS in Neurobiology, Physiology, and Behavior from the University of California, Davis and a PhD in Neuroscience and Cognitive Science from the University of Maryland, College Park (UMD). She was trained in the acquisition and analysis of electroencephalography (EEG) at the UMD as well as in functional Magnetic Research Imaging at the National Institutes of Health (NIH) and the Georgetown University Medical Center. In addition to her scientific training, she has over a decade of experience with research administration and program management, ranging from her work at the National Science Foundation and the White House Office of Science and Technology Policy to her responsibilities as a study manager for NIH, USUHS, Walter Reed National Military Medical Center and WRIISC clinical studies. This has afforded her considerable experience with Federal government program management, budgeting, regulatory compliance and science policy. In addition, she has served as a reviewer for peer-reviewed journals, IRB scientific review and successfully acquired grant funding during her appointment at the VA.  Dr. Costanzo is leading the research team in developing the next generation of rehabilitation, treatment and diagnosis for Veterans through leveraging both clinical and research resources that the VA currently offers and through partnership with other institutions.

Contact Dr. Costanzo at: 202-745-8000, ext. 56973.

< back to top

Lucas E. Crock, MA
  • Position: Health Science Specialist

Mr. Crock is a Health Science Specialist with the DC WRIISC. He has a BS in Psychology from King’s College, Wilkes-Barre, PA, and a MA in Psychological Science from the Catholic University of America in Washington, DC. His background includes conducting research on a variety of topics such as group therapy treatments, moderators for intervention efficacy, and treatments for Gulf War Illness. He is currently involved in multiple studies with the WRIISC examining the efficacy of alternative treatments for Gulf War Illness, telehealth interventions, and treatments for Insomnia in Veterans.

Contact Mr. Crock at: 202-745-8000, ext. 57553.

< back to top

Sharon DeMocker, MD
  • Position: Medical Director

Dr. DeMocker is the WRIISC-DC Medical Director. Dr. DeMocker previously headed an Integrative Medical clinic near Asheville, NC for over a decade, which she founded following her training with Dr. Andrew Weil at the University of Arizona, the first postdoctoral Integrative Medicine training center in the country. She completed her residency in Family Medicine through UVA in Lynchburg, with a focus on healthy lifestyle choices to prevent disease, which included her first clinical training with Dr. Weil. During medical school at the Medical University of South Carolina, she was involved in research on the physical and psychological aftermath of trauma. Dr. DeMocker has a strong interest in optimizing health through diet and lifestyle changes, as well as evidence-based, non-pharmaceutical treatments for treating chronic conditions, such as acupuncture, yoga, meditation and bodywork, including physical therapy, myofascial release and Therapeutic Touch. Dr. DeMocker is leading the WRIISC clinical team in expanding access to post-deployment health evaluation services for Veterans with deployment-related health and exposure concerns, and developing and expanding resources to assist VA providers in bringing the highest quality care to our nation’s Veterans.

Contact Dr. DeMocker at: 202-745-8249.

< back to top

Arghavan Hamedi, MA
  • Position: Health Science Specialist

Ms. Hamedi, MA, is a Health Science Specialist at the D.C. WRIISC. She has a B.A. in Psychology from Virginia Commonwealth University and an M.A. in Psychological Science from the Catholic University of America. Her research background in cognitive psychology includes examining a variety of topics such as emotion regulation, rumination, and brief mindfulness-based interventions. She was also an advanced cognitive brain trainer and eye-tracking coder. Her clinical research background involves military suicide prevention with active duty service members and investigating the role of attentional biases on suicide ideation. Ms. Hamedi is excited to work with the WRIISC team to help them meet their research goals and provide excellent patient care.

Contact Ms. Hamedi at: 202-745-8000, ext. 56824.

< back to top

Walt Jachimowicz, MSN, RN, CNL
  • Position:Nurse Educator

Mr. Jachimowicz is a registered nurse who serves as the Director of Education for the DC WRIISC. He obtained his BSN from Madonna University and his MSN from the University of Detroit Mercy. He has worked for the Department of Veterans Affairs Healthcare System since 1998 and has served in the United States Marine Corps as an active duty reserve officer. Mr. Jachimowicz has many years of experience working in the direct patient care setting and providing education to Veterans and their families. Mr. Jachimowicz has a strong interest in health promotion and disease prevention and set up the DC WRIISC Whole Health Coaching Clinic. Our DC WRIISC Veterans now spend time with health coaches that help them  figure out what their personal health and wellness goals are, how they intersect and affect them holistically and help them develop strategies to meet their wellness goals which may include reducing stress, improving sleep, lowering risk of chronic illness, and/or losing weight.

Contact Mr. Jachimowicz at: 202-745-8000, ext. 52636.

< back to top

Rebecca McCullers, MA, RN, RYT, HWC
  • Position: Health Coach

Ms. McCullers is a Registered Nurse, Registered Yoga Instructor, and Certified Health and Wellness Coach who supports the DC-WRIISC through health and wellness coaching. She served in the United States Air Force for 23 years as an officer, leader, nurse, and Inspector General. She earned her BSN from the University of North Carolina at Charlotte, a MA in International Relations from Webster University, and a Certification in Health and Wellness Coaching from Georgetown University. Ms. McCullers has worked in many diverse clinical and operational settings in the military health care system. She is passionate about health promotion and wellness and how these practices can help Veterans with chronic multi-symptom illnesses. Ms. McCullers believes in the transformative power of taking charge of your health, and engaging in holistic and integrative health practices to optimize overall well-being.

Contact Ms. McCullers at 202-745-8249.

< back to top

Kamila Pollin, PhD
  • Position: Advanced Postdoctoral Research Fellow

Dr. Kamila Pollin is an Advanced Postdoctoral Research Fellow with the DC WRIISC. She completed her undergraduate degree at Rutgers University and her PhD in Applied Physiology from the University of Delaware. Her dissertation examined the impact of dietary sodium on cerebral blood flow regulation in healthy, young adults. Her research interests include understanding the impact of nutrition and exercise on health outcomes. She is excited to join the team and support research projects aiming to assist with post-deployment health concerns from Veterans.

Contact Dr. Pollin at: 202-745-8249.

< back to top

Michelle Kennedy Prisco, MSN, ANP-C
  • Position: Environmental Exposure Specialist

Ms. Prisco is an adult nurse practitioner who works with the DC WRIISC clinical team on environmental exposure assessments. She obtained her BBA from the University of Notre Dame and her MSN from Yale University. She has worked at the Department of Veterans Affairs since 1994 and was an Army Nurse Corps Officer in the United States Army Reserve. She has published a number of articles and book chapters in the areas of post-deployment health and infectious disease.  Ms. Prisco was the Principal Investigator for a VA Merit Grant that explored how complementary and alternative medicine affected combat Veterans with PTSD-related sleep difficulties. She also was a co-investigator for a VA funded study that looked at an Environmental Exposure Assessment Tool for combat Veterans returning from Iraq and/or Afghanistan. Ms. Prisco’s research interests include public policy issues, environmental exposure concerns, web-based educational programming, and complementary and alternative medicine. She also is the DC WRIISC webmaster.

Contact Ms. Prisco at: 202-745-8000, ext. 56235.

< back to top

Immanuel Samuel, PhD
  • Position: Research Bioengineer

Dr. Samuel is a neuroscientist with the DC WRIISC. He completed Post-Doctoral training and graduated with a PhD in Biomedical Engineering at the University of Florida. His training is in neuro-informatics with exposure to the following: EEG, ECG, Local Field Potentials, Spectral Analysis, Connectivity, biostatistics, MRI (T1, T2, DTI, Functional). His current area of research is in biomedical research, artificial intelligence and neuroscience to examine general health and mental health outcomes for Veterans. He currently oversees studies on the effects of TBI on psychological outcomes, neuroimaging (EEG, ECG, MRI) and other TBI markers. His software development experience has helped develop computerized testing for studies at WRIISC DC. He also leads and collaborates on studies with open datasets and nation-wide big data research (BRAIN study).

Contact Dr. Samuel at: 202-745-8249.

< back to top

Rachel Stewart, PhD, LICSW
  • Positions:
    • Social Worker
    • Statistical Support

Dr. Rachel Stewart is a Licensed Independent Clinical Social Worker in the District of Columbia. After receiving her BA degree from the University of Notre Dame, Dr. Stewart went on to receive her MSW and PhD from the National Catholic School of Social Service at Catholic University. Dr. Stewart worked for many years in the private sector specializing in serious mental illness in the hospital, residential, and outpatient settings. Since coming to the VA, Dr. Stewart has served primarily in the Emergency Department where she was instrumental in the development and implementation of the Fast Track program. Dr. Stewart is honored to continue learning from her colleagues and the Veteran community at the Washington, DC WRIISC.

Contact Dr. Stewart at 202-745-8000, ext. 54647.

< back to top

Maria M. Valmas, PhD
  • Position: Advanced Clinical and Research Fellow

Dr. Maria M. Valmas is a Postdoctoral Fellow in Neuropsychology at the WRIISC-DC. She completed her undergraduate degree at Marymount University in Arlington, VA and her master's degree in Psychology at Boston University. She completed her MA and PhD in Clinical Psychology with a Neuropsychology Emphasis at Suffolk University in Boston, MA. For her dissertation she examined frontally-meditated behaviors and brain structure in alcoholism in collaboration with the Boston VA Healthcare System and the Boston University School of Medicine. Her training includes an APA-accredited internship in Clinical Psychology with a Neuropsychology Major Area of Study at the St. Cloud VA Healthcare system. Most recently, she completed postdoctoral clinical training in the Neuropsychological and Psychological Assessment clinic at Cambridge Health Alliance, Department of Psychiatry, Harvard Medical School. Her clinical interests include considering multiple neurocognitive, medical and psychiatric conditions within multicultural and intersectional contexts. Her research interests include examining relationships between cognition and neuroimaging and overlapping psychiatric and cognitive difficulties that can occur in the context of substance use, PTSD and a history of head injury.

Contact Dr. Valmas at: 202-745-8000 ext. 55644

< back to top

WenGuo Yao, BS, MS
  • Position: Health Science Specialist / Clinical Coordinator

Mr. Yao holds a bachelor’s degree in biology and a master’s degree in computer science. He plays a key role in coordinating clinical referrals participating in the War Related Illness and Injury Study Center’s National Referral Program.

Contact Mr. Yao at: 202-745-8000, ext. 57554.

< back to top