Meet our team at Summit Malibu in beautiful Malibu, California where we have experience in treating drug and alcohol addictions, with great success.  We’re with you every step in the process from before and after treatment. Get to know our team below.


William Oswald, Chief Executive Officer, and Founder

Summit Malibu was founded by William Oswald, who has over 40 years of experience in the field of substance use, addiction treatment, and mental health recovery.

As a hands-on owner in recovery himself, William has handcrafted the Summit Malibu treatment program by drawing upon his extensive experience with proven methods for long-term success. Read More

nicholas mathews

Nicholas Mathews, CFO

Nicholas Mathews is a passionate and committed treatment provider in every aspect of his professional life. A resident of Southern California by way of Oregon, He started his career in behavioral health as a result of his own profound experiences with personal recovery and knew his passion lied with giving back to a population of his peers. Mr. Mathews is a serial healthcare entrepreneur with every venture he undertakes dedicated to helping individuals struggling with addiction and mental health disorders.

Medical Team

Abraham Malkin

Abraham Malkin, M.D., Medical Director

Dr. Malkin is dual Board Certified in Family Medicine and Addiction Medicine. He is the Founder of Concierge MD Los Angeles; a nationwide concierge medical practice, and Drip Hydration; an on-demand IV Hydration and Wellness company. Dr. Malkin received his combined MD/MBA degree from Tufts University School of Medicine. He then completed his Family Medicine Residency training at Kaiser Permanente in the Los Angeles area.

Harsh Brar

Harsh Brar, N.P.

Harsh Brar is a Board Certified Family Nurse Practitioner. Harsh received his Bachelor of Science in Nursing from West Coast University in Los Angeles and his Master of Science in Nursing from Samuel Merritt University in Oakland. Harsh has a special interest in a variety of different medicines including addiction, concierge, and pain.

Erika Kamish, P.A.

Erika Kamish, P.A.

Erika Kamish is a nationally board-certified Physician Assistant and is licensed by the California Physician Assistant Committee. She received her bachelor’s degree at Yeshiva University in NYC before attending Western University of Health Sciences’ physician assistant program. Erika has a special interest in primary care, addiction and aesthetic medicine.

Shahla Modir, M.D.

Dr. Shahla Modir, M.D., has over 20 years of experience in addiction, psychiatry, and integrative medicine.

Dr. Modir is dual board-certified in Addiction and Psychiatry, serving as a diplomate of the American Board of Psychiatry and Neurology and its Addiction Psychiatry certification. Read More

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Kevin Simonson, Psychiatrist

Dr. Kevin is a psychiatrist with an integrative approach to mental health treatment. He completed his BS in Molecular Biology with minors in Chemistry and Psychology at Humboldt State University. He received his medical degree from UC Irvine and completed residency at UC Riverside and the Long Beach VA, where he worked in substance treatment and suboxone clinics.

Anna Corson, LAc, MTOM, Acupuncturist

Anna Corson, LAc, MTOM, Acupuncturist

Anna is a California Board Certified Acupuncturist and Herbalist with a specialty in helping patients recovering from trauma, mental health disorders, and compulsive behaviors. She guides her patients to reconnect to their hearts and find the answers they have been looking for from within.
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Jessica Green, Doctor of Chiropractic

Jessica Green, Doctor of Chiropractic

Dr. Jessica Green started her professional journey at UCSD where she received her BS degree. She continued to Cleveland Chiropractic College of Los Angeles where she graduated with her DC degree. Jessica has been licensed since March of 2011 although she continues to further her education so that she can better assist those in pain.
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Heather Mahoney, Massage Therapist

Heather is the founder of Trusted Touch Therapy. Graduating with a Masters degree in Spiritual Psychology from the University of Santa Monica, she has nearly twenty years of experience in therapeutic massage.
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Kam Walton, Program Director

Kam Walton brings her background in management to our team at Summit Malibu. Prior to joining Summit in 2022, she was a communications major at UCSD and SDSU.

Kam has worked in the field of addiction treatment since 2017 and takes a personal interest in all Summit employees as well as clients. Read More

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Amaris Baker, LMFT, Clinical Director

Amaris Baker is a graduate from the University of Nebraska-Lincoln where she earned her Bachelor of Arts (BA) in Psychology and minored in Sociology.

She obtained her master’s degree (MA) in Counseling: Marriage and Family Therapy at California State University-Long Beach. Read More

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Brooke Schwengel, Director of Nursing

Brooke is the Director of Nursing for Summit Malibu Treatment Center. She holds a Bachelor of Science in Nursing degree. Prior to working in mental health and addiction treatment, Brooke managed several clinics for covid testing. Read More

Clinical Team


Kelly Sweeney, Admissions & Aftercare Coordinator

Kelly Sweeney has worked in all aspects of the addiction and mental health treatment field for more than 16 years and currently serves as Case Manager and Aftercare Coordinator for Summit Malibu.

She has had the exclusive opportunity of working alongside some of world’s very best clinicians, treatment centers, and doctors. Read More

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Isabel Maddahi, AMFT, Primary Therapist

Born and raised in Los Angeles, California, Isabel Maddahi is a graduate from Loyola Marymount University (LMU). She first earned a Bachelor of Arts (BA) in Liberal Studies (Education) and minored in Studio Arts in 2018. In 2023, she returned to LMU to obtain her master’s degree (MA) in Marital and Family Therapy with Specialized Training in Art Therapy.

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Beth Farar, LMFT, Independently Affiliated Clinician

Beth Farar is a California State Licensed Marriage, Family and Child Psychotherapist (LMFT) who has been treating people for more than 22 years.

She specializes in working with individuals, couples, children, adolescents, and family therapy and is trained in Rapid Resolution Therapy. Read More

Gabriel Logan-Braun, Holistic Practitioner

Gabriel Logan-Braun has shared his knowledge and touched the lives of both our team and residents since arriving at Summit Malibu several years ago in 2018.

After going through a dark episode of depression in his late teens, he was led to his first yoga class at the age of 17, where he began his journey of healing and transformation. Read More

Rosemary Riggs

Rosemary Riggs, Equine-Assisted & Yoga Therapist

Rosemary Riggs provides a dual role as both an experienced Equine-Assisted Therapist and Yoga Therapist for our residents at Summit Malibu.

She facilitates therapeutic group and private sessions for our clients by navigating a myriad of life challenges including post-traumatic stress, anxiety, depression, and addiction. Read More

Annmarie Soul

Annmarie Soul, Yoga & Wellness Guide

Annmarie Soul has been teaching yoga and meditation for over 20 years. She is based out of Los Angeles’s Topanga Canyon where she is nestled in nature and sources strength from the peace and quiet of the native Chumash mountains. Annmarie did her yoga teacher training at Yoga Works in Santa Monica, CA where she then taught for 6 years. She also taught at Yoga Desa in Topanga canyon for over 15 years. Read More

Terry O’Rourke, CADC, Group Facilitator

After a successful career in film & tv production, Terry felt it was time to give back. He has been blessed in his life with many gifts and felt it was time to be of service to others. Terry’s mission statement is “I co-create a world of connection and discovery through supporting, facilitating, and loving myself and others.” He graduated from the UCLA Extension Addiction Studies Program In 2018. Terry then became a Certified Alcohol and Drug Counselor. He is also a certified SMART Recovery Facilitator.

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Jonathan Kim, CADC, Group Facilitator

Jonathan is a highly skilled and compassionate certified drug and alcohol counselor with extensive experience in helping individuals overcome substance abuse and addiction. With a genuine passion for making a positive impact on people’s lives, Jonathan has dedicated his career to guiding individuals through the challenges of addiction and providing them with the tools they need to achieve lasting recovery. Read More

Avi Nimmer, NLP Practitioner

Avi Nimmer, NLP Practitioner

Avi Nimmer is a Certified Master Neuro-Linguistic Programming Practitioner (NLP). He is passionate about helping others transform, elevate and awaken their consciousness; thus enabling them to return to their most authentic selves. Avi combines his knowledge of movement, mindfulness, energetic healing, breathwork and meditation to support clients on their journey of self-empowerment. He focuses on awareness and expanding energy to enlighten those around him and reprogram their mental state.

Support Staff


Donald Peake, Lead Clinician Assistant

Don Peake was born and raised in Seattle, Washington, and moved to the Los Angeles area in the early ’70s with his wife Pam.

He draws from his own personal experience in recovery when sharing with clients and offering compassion and encouragement during their time in treatment and beyond. Read More

Scott Naslund, Lead Clinician Assistant

Scott is a graduate of UCLA and has been working at Summit Malibu since its inception. His experience in recovery has been both challenging and rewarding. The challenge has lied in helping people through the throes of addiction by being supportive. The reward from witnessing people heal through Summit’s therapeutic process and rekindle their fire for life. His passion for learning has helped him realize the importance of helping people and the value of sobriety.

Jesse Alldredge

Jesse Alldredge, Clinician Assistant/TMS Technician

Jesse Alldredge has worked in the field of recovery since 2020. He is passionate about working with others while using his own personal experience to help guide them. Jesse is an Alabama native and came to California in April of 2022. He is compassionate and enjoys sharing his journey with the clients at Summit.

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Rosalia Sandoval, Facility Manager

Rosalia Sandoval has been a member of the Summit Malibu Team from day 1 and excels as our Facility Manager.

She enjoys interacting with our clients and staff, and is present every day, welcoming Summit Malibu with a fresh breakfast and a warm smile. Read More

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Mark Rabbene, Executive Chef

Chef Mark Rabbene attended the Culinary Institute of America and began his career in the food industry in 1983. He has held many titles such as Apprentice at Four Seasons Restaurant, Corporate Chef for AT&T, and has been the owner of two restaurants back in his hometown of New York. Read More