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Sarah M. Clark, PhD

Academic Title:


Primary Appointment:



685 W. Baltimore

Phone (Primary):


Education and Training

  • University of Toledo, BS, Biology, 2003
  • University of Maryland Baltimore, Ph.D., Neuropharmacology, 2011
  • University of Maryland School of Medicine, Postdoctoral training, Psychoneuroimmunology, 2011-2015


I am currently an Instructor in the Department of Psychiatry, investigating neuroimmune mechanisms associated with risk and resilience to the development of psychiatric disorders, including depression and anxiety.

My research is conducted as part of the Laboratory of Behavioral Neuroimmunology, with Dr. Leonardo Tonelli and in close collaboration with the labs of Dr. Robbie Schwartz of the Maryland Psychiatric Research Center and Dr. Todd Gould.  Using rodents to model aspects of human psychiatric disorders, such as PTSD and schizophrenia, we have examined how the adaptive immune system, and T cells specifically, can impact neurodevelopment, stress responsivity, emotionality and cognitive function across the lifespan. This research has allowed us to identify CD8+ T cells as modulators of cytokine responses to stress and recognize a role for CD4+ T cells in promoting adaptive learning and memory processes. We have also revealed a critical role for the adaptive immune system in the development of social behavior and spatial memory and cognitive flexibility. Finally, using a combination of rodent and human studies, we are elucidating how the immune and kynurenine systems intersect, resulting in dysregulation of the kynurenine pathway concurrent with behavioral and cognitive changes.

Prior to joining Dr. Tonelli’s lab, I completed my Ph.D. on adult hippocampal neurogenesis in the Ts65Dn mouse model of Down syndrome in the lab of Dr. Paul Yarowsky, here at the University of Maryland Baltimore.  I studied how gene dosage imbalances impacted proliferation and maturation of new neurons with a focus on potential therapies, including SSRIs and antioxidants, to rescue deficits in structural plasticity and cognitive function. Ultimately, my research interests reside in hippocampal function and how modulation of neurogenesis, whether by stress, immune activation or a combination of both, can influence behavior and cognition.

Research/Clinical Keywords

psychoneuroimmunology, T cells, stress, behavior, hippocampus, neurogenesis

Highlighted Publications

Clark SM, Soroka JA, Song C, Li X, Tonelli LH. CD4+ T cells confer anxiolytic and antidepressant-like effects, but enhance fear memory processes in Rag2-/- mice. Stress. 2016 May;19(3):303-11. doi: 10.1080/10253890.2016.1191466

Clark SM, Pocivavsek A, Nicholson JD, Notarangelo FM, Langenberg P, McMahon RP, Kleinman JE, Hyde TM, Stiller J, Postolache TT, Schwarcz R, Tonelli LH. Reduced kynurenine pathway metabolism and cytokine expression in the prefrontal cortex of depressed individuals. J Psychiatry Neurosci. 2016 Apr 11;41(4):150226. doi: 10.1503/jpn.150226. 

Clark SM, Sand, J, Francis, T., Nagaraju, A, Michael, KC, Keegan, AD, Kusnecov, A, Gould, TD, and Tonelli, LH. Immune status influences fear and anxiety responses in mice after acute stress exposure. Brain Behav Immun. 2014. May; 38:192-201. doi: 10.1016/j.bbi.2014.02.001.

Clark S, Schwalbe J, Stasko MR, Yarowsky PJ, Costa AC. Fluoxetine rescues deficient neurogenesis in hippocampus of the Ts65Dn mouse model for Down syndrome. Exp Neurol. 2006 Jul; 200(1):256-61. Epub 2006 Apr 19.






Research Interests

Awards and Affiliations

2002   The Honor Society of Phi Kappa Phi, University of Toledo 

2003   NIH Training Grant for Neuroscience

2013  Outstanding Trainee Poster Presentation, Dept. Psychiatry Annual Research Day, University of Maryland

2014  Outstanding Trainee Poster Presentation, $1500 Travel Award, Dept. Psychiatry Annual Research Day, University of Maryland