About The Anxiety Treatment Center of Greenwich


The Anxiety Treatment Center of Greenwich was founded by Jill Vaughan Tesei and Maryellen Pachler Kennell to provide expert, compassionate care for children, adolescents, and adults struggling with anxiety and related disorders. With a strong foundation in evidence-based practices and a deep understanding of both developmental and adult psychology, the center specializes in Cognitive Behavioral Therapy (CBT), parent guidance, Genomind genetic testing, and psychopharmacological support. ATC Greenwich is committed to helping individuals and families navigate anxiety with clarity, confidence, and proven therapeutic methods.

What Makes Us Different

At The Anxiety Treatment Center of Greenwich, we’re not a general mental health clinic—we're specialists in treating anxiety and related disorders in children, teens, and adults. Our approach is rooted in clinical expertise, compassion, and a deep understanding of how anxiety uniquely affects young minds and their families.

We specialize in the treatment of anxiety disorders, phobias, and Obsessive-Compulsive Disorder (OCD), offering advanced, targeted care that goes beyond general therapy.

We rely on Cognitive Behavioral Therapy (CBT)—the gold standard in anxiety treatment—and other proven techniques to help children, adolescents, and adults build real-world coping skills. Our practice also offers innovative options like virtual reality therapy for fears, phobias, and OCD, as well as Genomind genetic testing to support personalized treatment planning.

Parents are not just observers; they’re part of the process. We actively involve families as partners in therapy, guiding them to support their child outside of sessions.


Our team

Maryellen Pachler Kennell, APRN

Maryellen Pachler Kennell is a board-certified Nurse Practitioner specializing in child and adolescent psychiatry. She earned her nursing, master’s, and post-master’s degrees from Yale University. Before entering private practice, Maryellen worked as a clinical researcher at the Yale Child Study Center, where she contributed to the Research Unit in Pediatric Psychopharmacology (RUPP). Her research focused on developing and testing medications for children with serious psychiatric conditions.


Maryellen’s clinical expertise includes treating Depression, ADHD, Tic Disorders, and Trichotillomania, as well as providing Behavioral Parent Training and developmental guidance. She specializes in the Cognitive-Behavioral Treatment of anxiety disorders and Obsessive-Compulsive Disorder in youth. As the lead clinician in a study evaluating CBT for childhood anxiety in primary care settings, she also has extensive experience working with high school and college athletes experiencing performance anxiety. A respected voice in the field, Maryellen has co-authored over ten publications, lectured nationally and internationally, and currently serves as a lecturer at the Yale University School of Nursing.

Jill Vaughan Tesei,  APRN

Jill Vaughan Tesei is a board-certified Family Psychiatric Nurse Practitioner with advanced training in child and adolescent mental health. She received her degree from Yale University and also holds Master’s degrees in Clinical Mental Health Counseling and Expressive Arts Therapies from Lesley University. Jill completed specialized training in psychopharmacology, Cognitive Behavioral Therapy, and Behavioral Parent Training through the Yale Child Study Center, and further developed her CBT expertise at the Beck Institute at the University of Pennsylvania.



With over two decades of experience across inpatient, residential, and emergency psychiatric settings, Jill now focuses on the private practice treatment of anxiety and related disorders in children, adolescents, and adults. She is fully licensed and sees many adult clients, with a special emphasis on anxiety disorders, including Panic Disorder, Generalized Anxiety Disorder, Social and Separation Anxiety, Phobias, and OCD. Jill also has training in Habit Reversal Therapy for tic disorders and Trichotillomania.

She has studied under leading experts such as Philip Kendall, Tamar Chansky, and John March, and currently teaches child psychiatry as a clinical professor at the Yale University School of Nursing.