Principal Investigator
Zachary Cohen, Ph.D.
Dr. Zachary Cohen is Director of the Personalized Treatment Lab and an Assistant Professor in the Department of Psychology (Clinical Area) at the University of Arizona. His research focuses on precision mental health treatments, aiming to answer the questions “How and For Whom do Treatments Work?” through data-driven approaches. His work integrates advanced quantitative methods, including machine learning, to develop clinical prediction models and decision support tools that personalize treatment. Some of Dr. Cohen’s key contributions include the development of the Personalized Advantage Index (PAI), co-creating the RainFrog Digital Therapy ecosystem (a platform designed for scalable, evidence-based psychological interventions) with his mentor Dr. Michelle Craske at the UCLA Depression Grand Challenge, and designing and launching several mental health digital phenotyping studies. His work seeks to improve mental health treatment accessibility and improve outcomes, particularly for underserved populations. In his free time, Dr. Cohen enjoys cooking, gardening, and spending time with his wife and kiddos.
Postdoctoral Research Fellow
Julia Yarrington, Ph.D.
Dr. Julia Yarrington is a Postdoctoral Research Fellow in the Personalized Treatment Lab. Dr. Yarrington completed her Ph.D. in Clinical Psychology under the mentorship of Dr. Michelle Craske at the University of California, Los Angeles. She completed her APA-accredited clinical internship at the West Los Angeles VA. Her research interests center on risk and novel, personalized treatments for common mental health problems including depression, anxiety, and suicidal ideation. She studies emotional, cognitive, and health-related risk factors for these conditions and is especially interested in the dissemination and implementation of self-guided and coach-supported digital interventions. Clinically, Dr. Yarrington specializes in treating anxiety, depression, and trauma. Within the PTL, Dr. Yarrington supports several ongoing studies, including the launch of a digital therapy ecosystem at the U of A and provides clinical and research supervision to doctoral students. In her free time, she enjoys running, spending time with her family, reading Stephen King novels, and exploring new restaurants.
Graduate Students
Nate Choukas
Nate is a third-year graduate student in clinical psychology under the primary mentorship of Dr. Zachary Cohen. His primary line of research focuses on developing a formal network theory of PTSD, using computational modeling and complex systems science to understand the dynamic mechanisms that maintain posttraumatic distress. He integrates network psychometrics with intensive longitudinal data (ILD) methods, such as ecological momentary assessment (EMA) and passive sensing, to examine real-world symptom dynamics, psychological processes, and individual differences in treatment response. Nate also works on developing and evaluating scalable, personalized digital mental health interventions for diverse populations. In his free time, he enjoys playing golf, making music, exercising, and spending time with family and friends.
Torsa Chattoraj
Torsa is a second-year graduate student in clinical psychology under the primary mentorship of Dr. Cohen, previously holding an MA in Psychology with a specialization in Clinical Psychology from India. Her research interests are focused on culturally adapting evidence-based treatments and employing predictive modeling for personalized interventions. She is particularly interested in understanding the long-term impacts of adverse experiences, social adjustment, and emotion regulation. Her clinical experience with children at correctional centers and rehabilitation homes strengthens her efforts towards developing scalable psychological interventions for minoritized youth. In her spare time, Torsa loves propagating plants, making poor attempts at reimagining Van Gogh paintings, and re-reading comfort books.
Dawson Haddox
Dawson is a first-year clinical psychology graduate student working with Dr. Cohen. He applies data science methods to intensive longitudinal data to improve how we conceptualize, measure, and predict mental health and therapeutic change. Dawson is particularly interested in integrating artificial intelligence and passive sensing data from smartphones and wearables to create scalable, personalized digital interventions. He is also interested in clinical psychometrics, as well as the structure and temporal dynamics of psychopathology and treatment response. In his leisure time, he enjoys exercising, reading, playing computer and roleplaying games, and spending time with family and friends.
Research Staff
Angela White
Angela is Lab Manager of the Personalized Treatment Lab. She holds a dual Bachelor of Science in Psychological Science and Neuroscience and Cognitive Science, with an emphasis in Neurobiology. Under Dr. Cohen’s mentorship as an undergraduate honors student, Angela founded the Leveraging Exercise for Anxiety and Depression (LEAD) study, which employs scalable research methods to design, deliver and study exercise interventions for individuals suffering from anxiety and depression. Using an interdisciplinary approach, LEAD aims to support the development and delivery of accessible, effective, personalized treatments and propel the integration of exercise-based treatment into clinical practice. Angela plans to pursue a doctorate in clinical psychology at the University of Arizona. She is a longtime yoga practitioner and teacher, and loves traveling, hiking, baking, and spending time with family and friends.
Jon Logan-Rung
Jon is Head of Clinical Content Development in the Personalized Treatment Lab. He holds a bachelor’s degree in sociology from Wesleyan University and a master’s degree in English from the University of Arizona. His primary research interest is childhood trauma and its psychological, neurological, and physiological impacts throughout the lifespan. He hopes to pursue a doctorate in clinical psychology and spend his time delivering, researching, and writing about trauma interventions. In his free time he lifts weights and eats extra chicken.
Research Assistants
Zane Burrows
Zane is a postbaccalaureate research assistant in the Personalized Treatment Lab who initially joined the team as an undergraduate honors student. He holds a Bachelor of Science in Psychological Science and a minor in Business Entrepreneurship and Innovation. Zane is currently serving as a certified peer coach within RainFrog and has worked as a member of the ALACRITY Sensor Pilot project. He aspires to earn a doctorate in clinical psychology and create his own digital mental health intervention. Zane is passionate about researching personalized digital mental health interventions focusing on active and passive sensor data. In his free time, he enjoys hiking, reading, and making music.
Tanner Valus
Tanner is a graduate research assistant in the Personalized Treatment Lab. He is currently pursuing a Psy.D. in clinical psychology at Florida Institute of Technology and holds a B.S. in Psychological Science from the University of Arizona. His research interests are the intersection between Christianity and psychology as well as PTSD/Trauma with an emphasis on the military and combat veterans. He plans to attend graduate school for a Ph.D. in Clinical Psychology and become a clinical psychologist in private practice or work for Veterans Affairs. In his free time, Tanner enjoys playing sports, going to the gym, and spending time with friends.
Ella Salem
Ella is a postbaccalaureate research assistant in the Personalized Treatment Lab who initially joined the team as an undergraduate honors student. She is currently working as a certified peer coach within RainFrog and has formerly served as a member of the RainFrog content review team and the ALACRITY Sensor Pilot project. Ella is interested in studying and developing interventions for eating disorders and obsessive-compulsive disorder (OCD). She holds a Bachelor of Science in Psychological Science and hopes to obtain a doctorate in clinical psychology. In her free time, she loves to play tennis, practice yoga, and spend time with friends.
Collin Kriegbaum
Collin is a graduate research assistant in the Personalized Treatment Lab. He is currently pursuing a doctorate in clinical psychology at Ohio State University and holds degrees in Clinical Psychology (M.A.) and Quantitative Psychology (M.S.) from Ball State University. Collin serves as a certified peer coach within RainFrog and has formerly worked on the RainFrog content review team. His research interests lie in personalizing digital treatments, improving adherence in digital therapies, and cognitive behavioral therapy (CBT) processes. He is also interested in research on the etiology and treatment of anxiety disorders, with a focus on social anxiety. After he obtains his doctorate, Collin intends to be a psychological researcher who also maintains a small clinical practice. In his free time, he enjoys woodworking and playing guitar.
Sara Moore
Sara is a postbaccalaureate research assistant in the Personalized Treatment Lab. She primarily works on RainFrog, both as a part of the content review team and as a certified peer coach. She holds a Bachelor of Arts in Psychology and wishes to obtain a Doctorate in Clinical Psychology. Sara is interested in improving the diagnosis and treatment of ADHD in women and girls. In her free time, she enjoys reading, crafting, and watching sitcoms.
Ashley Bohan
Ashley is a postbaccalaureate research assistant in the Personalized Treatment Lab, having initially joined the team as an undergraduate student. She currently serves as a member of the RainFrog content review team. Her research interests include studying and developing interventions for sleep, anxiety, and other mood disorders. She holds a Bachelor of Science in Psychological Science with minors in Public Health and Physiology and Medical Sciences, and she plans to pursue graduate or professional training in mental health. Ashley is particularly interested in the intersection of psychological and medical approaches to treating mood and anxiety disorders. In her free time, she enjoys watching college basketball, listening to music, and spending time with friends.
Robyn Stea
Robyn is a graduate research assistant in the Personalized Treatment Lab. She holds a Bachelor of Science in Psychological Sciences from the University of Arizona and is currently pursuing a Master of Arts in Art & Visual Culture Education. Her interests focus on the intersection of art and psychology, particularly how creative expression can support emotional well-being. She plans to pursue a doctorate in psychology with the goal of becoming a licensed clinical psychologist. Outside of her academic pursuits she enjoys painting, drawing, printmaking, and darkroom photography.
Aidan Rains
Aidan is an undergraduate research assistant in the Personalized Treatment Lab. He is currently majoring in Psychology (B.A.) at the University of Arizona. His research interests lie in personalized mental health treatment, with a focus on using data and predictive modeling to improve therapy delivery. He is particularly interested in anxiety and depression, and has an additional interest in substance use and recovery. Aidan’s future goal is to earn a Doctorate of Psychology and work as a clinical psychologist. In his free time, he enjoys listening to music, going to concerts, and practicing photography.