David Randal Hessl, Ph.D. for UC Davis Health

David Randal Hessl, Ph.D.

Professor, Division of Clinical Psychiatry

To see if David Randal Hessl is accepting new patients, or for assistance finding a UC Davis doctor, please call 800-2-UCDAVIS (800-282-3284).



Clinical Psychology

Neurodevelopmental Disorders


Locations and Contact

UC Davis MIND Institute

UC Davis MIND Institute
2825 50th St.
Sacramento, CA 95817

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Additional Numbers

Clinic Phone


Physician Referrals

800-4-UCDAVIS (800-482-3284)

Philosophy of Care

My philosophy is first to be a good listener, to really appreciate the patient's perspective, their developmental background, and to approach children and those with disabilities at their level. I enjoy using humor and a casual style to connect with these patients. I always try to bring knowledge of disabilities through scientific inquiry into the assessment process.

Clinical Interests

Dr. Hessl is a clinical psychologist offering assessment, treatment recommendations and consultation to individuals with neurodevelopmental disorders. He has special clinical interest and expertise in fragile X-associated disorders, autism, ADHD, Down syndrome and intellectual disability.

Research/Academic Interests

Dr. Hessl directs the Translational Psychophysiology and Assessment Laboratory (T-PAL) at the MIND Institute to investigate the emotional psychophysiology of children with neurodevelopmental disorders, and to develop novel outcome measures for clinical trials.

He also conducts collaborative studies with other researchers, investigating brain imaging, molecular genetics and neuropsychology in an effort to understand links between genetics, brain function and behavior. His research focus is primarily on fragile X-associated disorders, such as fragile X syndrome and fragile X-associated tremor ataxia syndrome (FXTAS). His lab has contributed to the refinement or development of cognitive and behavioral assessments for people with disabilities.


Clinical Psychologist

Center/Program Affiliation

UC Davis MIND Institute
Center for Neuroscience

Undergraduate School

B.A., UCLA, Los Angeles CA 1989

Other School

Ph.D., Child Clinical Psychology and Developmental Psychology, University of Washington, Seattle WA 1997

Other School

M.S., Child Clinical Psychology, University of Washington, Seattle WA 1995


Lucile Packard Children's Hospital/Children's Health Council, Stanford University School of Medicine, Stanford CA 1996-1997


UC Berkeley, Berkeley CA 1997-1998

The John Merck Fun's Developmental Disabilities Translational Research Program Scholar, 2012

Jarrett Cole Clinical Award, National Fragile X Foundation, for “Dedicated Service to Families in the Worldwide Fragile X Community”, 2012

Dean’s Team Award for Excellence, UC Davis School of Medicine, 2009

UC Davis finalist - John Merck Scholars Program, Biology of Developmental Disabilities in Children, 2008

UC Davis Academic Senate Research Travel Award, 2008

Zafarullah M, Durbin-Johnson B, Fourie ES, Hessl DR, Rivera SM, Tassone F. Metabolomic Biomarkers Are Associated With Area of the Pons in Fragile X Premutation Carriers at Risk for Developing FXTAS. Front Psychiatry. 2021 Aug 16;12:691717. doi:10.3389/fpsyt.2021.691717. PMID:34483988.

Kaat AJ, McKenzie FJ, Shields RH, LaForte E, Coleman J, Michalak C, Hessl DR. Assessing processing speed among individuals with intellectual and developmental disabilities: A match-to-sample paradigm. Child Neuropsychol. 2022 Jan;28(1):1-13. doi:10.1080/09297049.2021.1938987. Epub 2021 Jun 14. PMID:34126855.

Hessl D, Libero L, Schneider A, Kerns C, Winder-Patel B, Heath B, Lee J, Coleman C, Sharma N, Solomon M, Nordahl CW, Amaral DG. Fear Potentiated Startle in Children With Autism Spectrum Disorder: Association With Anxiety Symptoms and Amygdala Volume. Autism Res. 2021 Mar;14(3):450-463. doi:10.1002/aur.2460. Epub 2020 Dec 29. PMID:33372389.

Solomon M, Gordon A, Iosif AM, Geddert R, Krug MK, Mundy P, Hessl D. Using the NIH Toolbox to Assess Cognition in Adolescents and Young Adults with Autism Spectrum Disorders. Autism Res. 2021 Mar;14(3):500-511. doi:10.1002/aur.2399. Epub 2020 Oct 2. PMID:33006263.

Westmark CJ, Kniss C, Sampene E, Wang A, Milunovich A, Elver K, Hessl D, Talboy A, Picker J, Haas-Givler B, Esler A, Gropman AL, Uy R, Erickson C, Velinov M, Tartaglia N, & Berry-Kravis EM. Soy-based infant formula is associated with an increased prevalence of comorbidities in fragile X syndrome. Nutrients. 2020;12(10):3136. doi:10.3390/nu12103136.

Zafarullah M, Palczewski G, Rivera SM, Hessl DR, Tassone F. Metabolic profiling reveals dysregulated lipid metabolism and potential biomarkers associated with the development and progression of Fragile X-Associated Tremor/Ataxia Syndrome (FXTAS). FASEB J. 2020 Dec;34(12):16676-16692. doi:10.1096/fj.202001880R. Epub 2020 Nov 1. PMID:33131090.

Scott H, Harvey DJ, Li Y, McLennan YA, Johnston CK, Shickman R, Piven J, Schweitzer JB, Hessl D. Cognitive Training Deep Dive: The Impact of Child, Training Behavior and Environmental Factors within a Controlled Trial of Cogmed for Fragile X Syndrome. Brain Sci. 2020 Sep 25;10(10):E671. doi:10.3390/brainsci10100671. PMID:32992879.

Luu S, Province H, Berry-Kravis E, Hagerman R, Hessl D, Vaidya D, Lozano R, Rosselot H, Erickson C, Kaufmann WE, Budimirovic DB. Response to Placebo in Fragile X Syndrome Clinical Trials: An Initial Analysis. Brain Sci. 2020 Sep 11;10(9):629. doi:10.3390/brainsci10090629. PMID:32932789.

Schneider A, Summers S, Tassone F, Seritan A, Hessl D, Hagerman P & Hagerman RJ.  Women with fragile X-associated tremor/ataxia syndrome. Movement Disorders Clinical Practice. 2020 Aug 31;7(8):910-919. doi:10.1002/mdc3.13084.

Zafarullah M, Tang H, Durbin-Johnson B, Fourie E, Hessl D, Rivera SM, & Tassone F. FMR1 locus isoforms: Potential biomarker candidates in fragile X-associated tremor/ataxia syndrome (FXTAS). Scientific Reports. 2020 Jul 6;10 (1):11099.