Our Team

Providing an Integrative Approach for Long-Term Results

Patient Focused

Compassionate Care

Experience and insight

Psychiatrist, Founder IPHC

Founder of Integrative Psychiatric Healing Center, Integrative Psychiatrist

Will Van Derveer, MD

After attending Vanderbilt University for medical school, Will came to Colorado for residency training in psychiatry at the University of Colorado. He opened his private practice in 2002, and has been in practice in Boulder since that time. Will is board-certified by the American Board of Integrative and Holistic Medicine. His passion is finding effective relief from psychological suffering using a vast array of the most natural approaches possible. In addition to traditional medical training, he has have received training in meditation instruction, shamanism, and various psychotherapies.

Successful treatments often include addressing imbalances from a variety of different perspectives, from the ground up. Beginning with diet and lifestyle habits, mindfulness training, optimization of gut functioning, treating hormone imbalances and signs of chronic stress, his aim is to address root causes. His recent experience (2012-2015) as a member of a research team conducting a Phase 2 double blind randomized controlled clinical trial of a novel treatment for chronic treatment PTSD (mdmaptsd.org) – further reinforced his conviction that everyone can heal and achieve well-being.

Will’s role at IPHC is medical director, psychotherapist, and psychiatrist, and no longer provides medication-only treatments. His practice is limited to people seeking weekly psychotherapy with integrative mindfulness-based psychiatry.

Integrative Psychiatrist

Elizabeth Cordes, DO

Elizabeth is a psychiatrist who practices medicine and sees health in a different way than a lot of other doctors. After receiving her undergraduate degree with honors in Medical Ethics from the University of Oklahoma in 1994, she went on to complete her medical degree at Oklahoma State University College of Osteopathic Medicine and residency in Psychiatry at Griffin Memorial Hospital in Norman, Oklahoma. She had a thriving private practice in Edmond, Oklahoma since 2002 prior to moving to Colorado in 2019 to join the Integrative Psychiatry Institute. Her long standing interest in Mind Body Medicine has prompted her to pursue extensive training in Integrative Medicine: becoming one of the first graduates of the inaugural NMWI Women’s Functional & Integrative Medicine Professional Training Program with Aviva Romm, MD, a member of the IPI-Integrative Psychiatry Fellowship class, as well as numerous programs with Andrew Weil, MD, James Greenblatt, MD and others. 

Elizabeth’s passion is helping individuals achieve optimal mental wellness through a root cause approach. She believes that the traditional model of mental health care is broken, incomplete, and does not fully support patients in recovery or wellness.  Furthermore, she believes in the natural healing capacity of the human body as well as the power of partnering with her patients in the pursuit of health. Elizabeth is an Accelerated Resolution Therapy trained therapist. She has also been a regional speaker on pharmacogenomic testing and utilizes genetic testing when appropriate in her evaluations.  As part of her commitment to Mind Body Medicine, she has completed a 200 hour yoga teacher certification and continues her studies of meditation and other Mind Body skills techniques.

Guili Zavaschi, MA

Guili is a Licensed Professional Counselor originally from Brazil, and completed his undergrad studies of psychology in South America and earned his master’s degree in Counseling in the United States where he has been living since 2008. He is passionate about supporting and guiding clients in resolving the roots of the issues that hold them back from a more vital and wholesome life.

Guili firmly believes that good a psychotherapeutic process should facilitate shifts in our awareness creating temporary modified states of consciousness. This perspective was consolidated and informed by his two and a half years of work in the Peruvian amazon jungle. In Peru, he worked as a psychotherapist in a rehabilitation center for addictions that combined modern medicine and psychotherapy with ancient shamanic practices. Through this experience he closely accompanied clients in navigating expanded states of consciousness and witnessed and experienced profound and positive changes in clients’ lives.

In order to achieve similar depths and results, he is collaborating with Integrative Psychiatry Healing Center and their team. He brings his experience of more than a decade actively working as a psychotherapist and his training in Gestalt therapy, Mindfulness, Functional Family Therapy and Wilderness therapy to contribute to clients journey of transformation.


Gestalt Therapy, Mindfulness
Wilderness Therapy, Functional Family Therapy


Naropa University, Transpersonal Psychology
Psychedelic Sitters School, Medicinal Mindfulness
EMDR Trained

Katie Markley, MA, LPC, LAC

Katie can best be described as valuing the relationships she builds with her clients and relaying the genuine sense that their lives matter.  She is passionate about altered states medicine work as she has witnessed their capacity to facilitate deep healing.

Drawing from her experience as a member of the Native American Church, Katie views the practice of Ketamine Assisted Psychotherapy to be an access point for clients to experience expanded states of consciousness.  She has worked with Medicinal Mindfulness as both a participant and assistant in their Psychedelic Sitters School, giving her much experience blending psychotherapy with altered states.

Katie graduated with a Transpersonal Psychology degree from Naropa University in 2012 and has since been seeing clients in private practice.  She is trained in EMDR and also served as an assistant in the Bridging Soma & Soul training where the most current methods, informed by neuroscience and somatic psychotherapy, are taught as practical techniques for supporting wholeness in others through nervous system integration and trauma healing.

Trainings, Consulting and Supervision

We provide training, master classes, consultations, and supervision at Integrative Pscyhiatric Healing Center. If you're interested in working with us, expanding your skill set, or receiving professional consultation in starting your own Ketamine clinic or improving your psychotherpy or psychiatric private practice, we can schedule a consultation to see how to best apply our expertise and experience.

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Discover long-term mental health with Integrative Psychiatry