Our Team

Samson Motavassel, LCSW, CGP, CCTP, is the Executive Director, therapist, and coach at CAST Treatment Centers. He earned his Bachelor’s degree in Psychology from the University of California, Los Angeles, and his Master’s degree in Clinical Social Work from the University of Southern California. Since 2009, Samson has worked in the field of mental health and wellness in a wide range of roles, with a focus on treating substance use disorders, co-occurring mental health conditions, and supporting systems of care through leadership and program development.

He has extensive experience treating anxiety, depression, addiction, bipolar disorder, and related mental health concerns. Additionally, Samson is a Certified Clinical Trauma Professional (CCTP) and Certified Grief Professional (CGP), with training in applying a trauma-informed approach to support individuals navigating trauma and loss. His therapeutic framework is solution-focused, strength-based, and highly individualized, aimed at empowering clients to create meaningful, lasting change.

As Executive Director, Samson collaborates closely with both clinical and administrative teams to cultivate a safe, supportive, and effective healing environment.

Sarah Leitz, LMFT,CSTS is the Clinical Manager and Therapist at CAST Treatment Centers. She earned her Bachelor’s degree in Psychology and Family Studies at the University of Arizona, and received her Master’s in Marital and Family Therapy from Alliant International University. Sarah has worked in the mental health field since 2016, providing comprehensive therapeutic services to individuals and families. Sarah has a strengths based approach focused on concrete solutions, personal growth and resiliency.

Patrick O’Neil, CADC-I, CAST’s Manager of Next Step Program and Group Facilitator. He has worked in the recovery field in various capacities since 2003. He is a published author of two memoirs and a co-contributor for instructional manuals on creative writing. Through embracing his own creative process he has recognized that nurturing and cultivating one’s passion is an integral and essential part of recovery.

Dr. William D. Stanley received his Doctorate of Medicine degree from UMDNJ – Robert Wood Johnson Medical School in Piscataway, NJ. He did his residency training at Albert Einstein Medical Center in Philadelphia, PA. He received his Bachelor of Science degree from Morgan State University in Baltimore, Md. He did 1 year of a Master’s program in Anatomy at the University of Maryland Baltimore City campus prior to matriculating to medical school that next year.

He has worked in Internal Medicine for the majority of his professional life both inpatient and outpatient. He started Parkside Medical Assoc, PA in Trenton, NJ, employing 4 physicians. He noticed he had an interest in substance abuse and started involvement with ASAM (American Society of Addiction Medicine) in 1998. He completed his Boards in ASAM in 2000 and, later, by ABAM (American Board of Addiction Medicine) in 2010. Since 2013 he has concentrated his time exclusively to the treatment of Substance Abuse Disorders. Prior to his joining Dr. Benya and her team in California, he was Medical Director of both an inpatient detox unit and 2 outpatient treatment programs, all located in New Jersey. He has an active license to practice medicine in both New Jersey and California.

Dr. Craig V. Smith, M.D. is a former organ transplant surgeon, who now dedicates his practice to addiction medicine. He received his M.D. degree from the UCLA School of Medicine. Dr. Smith then completed his general surgical residency at Harbor-UCLA medical center and his multi-organ transplant surgical fellowship at the University of Pittsburgh medical center. He returned to UCLA medical center to start his career in academic transplant surgery, performing transplants, teaching students and residents while also conducting research on transplantation for the treatment of diabetes. During his academic career as an associate professor of surgery, Dr. Smith performed more than 500 organ transplants at UCLA, UC Irvine and the City of Hope National Medical Center. Since alcohol and drug use are leading causes of organ damage leading to the need for a transplant, Dr. Smith learned about addiction by listening to his patients. More importantly, since a requirement to receive an organ transplant is abstinence from using alcohol and drugs, Dr. Smith learned about recovery from listening to his patients. After listening over the years, pursuing self-study and continuing medical education in the field of addiction, in 2009 Dr. Smith decided to dedicate his career to addiction medicine. Dr. Smith is board certified in Addiction Medicine by both the American Board of Preventive Medicine and the American Board of Addiction Medicine.

Kate Weaver, LMFT, is a Therapist at CAST Treatment Centers. She earned her Bachelor’s degree in Psychology and her Master’s degree in Clinical Psychology from Vanguard University of Southern California. Kate has worked in the mental health field in a variety of capacities, including community mental health, mental health/dual-diagnosis treatment programs, school-based therapy, and private practice settings. Kate uses an integrative clinical approach, drawing from relational, somatic, and strength-based psychotherapy. She is also a certified Brainspotting Practitioner.

Dr. Tom Wood is a Licensed Professional Clinical Counselor with more than
25 years of experience specializing in addictions and mental health.
Throughout his career, he has offered a wide range of services, including
addiction treatment, psychotherapy, and educational programs to
individuals, couples, families, and groups. Dr. Wood earned his Ph.D. in
Sociology, focusing on Addiction Studies and Family Systems, equipping him
with a deep understanding of the complexities of addiction, mental health
and the dynamics of family relationships. Dr. Wood is skilled in assessing
and treating individuals, families, and professionals dealing with diverse
challenges such as chemical dependency, behavioral addictions, emotional
and mental health concerns, trauma, family and relationship conflict as well
as personal lifecycle adjustment, career, and relationship transitions. Dr.
Wood is an experienced EMDR™ practitioner and a designated Master
Trainer for the Say It Straight™ program, a research-based education and
training program that results in empowering communication skills and
behaviors and is recognized by SAMHSA as an evidence-based program.

Ashley Nahai is a Licensed Marriage and Family Therapist. She received her BA in Psychology from UCLA in 2010 and her Masters in Marriage and Family Therapy from the University of Southern California in 2012. During graduate school, Ashley completed her practicum training at the residential level of care, where she received training in psychodynamic therapy, cognitive-behavioral therapy, and 12-step oriented treatment. Following her practicum, Ashley served as a Counseling Director at a residential substance abuse facility, for over 5 years. In this position, she created and oversaw daily programming for over 100 residents, as well as supervised substance abuse counselors and program technicians. Additionally, she provided individual and group psychotherapy and substance abuse counseling, as well as facilitated family therapy groups and sessions. Following her tenure, Ashley served as the Director of Mentoring and Family Programming at the outpatient level of care. In this position, Ashley directed and supervised case management services for over 60 clients and families, led clinical trainings and supervision for all case managers, and facilitated family therapy workshops for clients and their families. Additionally, Ashley runs a private practice in Los Angeles where she provides therapeutic services to individuals, couples, and families. Ashley believes in the sanctity of the therapeutic relationship and in the ability of every person to heal and recover.

Matthew is the Director of Admissions at Cast Centers, bringing valuable experience from the addiction treatment industry since 2021. As a member of the recovery community since 2018, he’s dedicated to connecting clients, staff, and partners to foster a supportive environment. Matthew’s passion for helping others shines through in his work.

Sara Kassabian is the Office Manager at CAST Centers, where she brings years of experience in the mental health and addiction treatment field. She earned her Master’s degree in Public Health from the University of California, Los Angeles, and is passionate about supporting individuals and teams in creating a healing, client-centered environment.

At CAST, Sara plays a key role in overseeing daily office operations, coordinating client care, and supporting both the clinical and administrative teams. From managing schedules and maintaining accurate records to facilitating smooth communication across departments, she ensures that the center runs efficiently and professionally in alignment with CAST’s mission.

Known for her compassionate presence and strong organizational skills, Sara is deeply committed to helping others—whether it’s clients, colleagues, or the community at large. Outside of work, she enjoys spending time with loved ones, practicing yoga, and caring for animals. She is proud to be part of the CAST team and fully believes in the organization’s mission to support lasting mental health and recovery.