Our Team


Sarah Seeling
Partial Hospitalization Therapist

Sarah aims to bring an accepting and inviting presence into her work at Center City Recovery to encourage positive change and growth. Sarah believes in treating each client with compassion through a person-centered, trauma-informed lens.

Sarah graduated with an undergraduate degree in psychology from Franklin and Marshall College and Master of Social Service degree from Bryn Mawr College. She is an EMDR trained therapist and incorporates mindfulness, CBT, psychodynamic, and strengths-based approaches into her work. Sarah has experience working as a psychotherapist in variety of settings treating mental health issues such as depression, anxiety, and PTSD as well as addiction, and has provided services to children, adolescents, and adults of all ages.


Juliana Collins
Intensive Outpatient Therapist

Julianna joined the Center City Recovery team with life experience and understanding of addiction. She followed her calling to the field of substance use recovery treatment believing strongly Philadelphia is in need of education and adequate treatment to address the growing addiction epidemic.

Juliana earned a Bachelor of Social Work from Temple University and her Master of Social Work from the University of Pennsylvania. She has experience working with multiple populations including child welfare case management, sexual assault crisis counseling, and is skilled in Dialectical Behavior Therapy. Juliana is passionate, empathetic, and consistent in walking side by side with clients through their recovery journey.

Denis A. Boyle
Medical Director

Dr. Denis Boyle graduated from Villanova University in 1972. He earned his Doctorate of Medicine from the Georgetown University School of Medicine and completed his Physical Medicine and Rehabilitation residency at the University of Pennsylvania.

Dr. Boyle also served as Lieutenant Commander in the Medical Corps of the United States Navy. Dr. Boyle is experienced in Medication Assisted Treatment (MAT) and works within the treatment team to meet the needs of each individual. As a seasoned medical professional, Dr. Boyle utilizes a multidisciplinary approach to maximize treatment success and compliment preventative care.

Cassandra Sierra
Chief Clinical Officer

Cassandra was the Founder/Chief Clinical Officer of Wellington Counseling and Associates, and New Options of Royal Palm Beach, Inc. which opened its doors in August 2005. WCA rebranded to Elevations Health, LLC., in 2016. Elevations Health was located in Wellington, FL, Coral Springs, FL, and Austin, TX. Cassandra sold Elevations Health in February 2018. Effective October 2018, she became the Director of Mental Health Services of the Recovery Team Behavioral Health in Palm Beach County. RTBH provides primary mental health services to persons affected with mental health illness. Our goal is to re-integrate our patients back into society and provide them with coping mechanism to manage their disability. Cassandra also provides training classes and CEU’s for mental health and substance abuse professionals. She works with many agencies in Palm Beach County as a consultant and corporate trainer. In addition, as a Life and Business Coach/Consultant, she has assisted many entrepreneurs to established and manage new business ventures in substance abuse treatment industry in Florida and in several states around the country.

Cassandra Sierra was employed by the Palm Beach County Health Department for 19 years. She served as the Staff Development and Training Manager and provided training for over 1,100 employees. She trained clerks, paraprofessionals, nurses, doctors, managers and senior management. She facilitated various training programs, (e.g. Executive Leadership Customer Service, Communication, Conflict Resolution, and Cultural Competency). Her work included consulting, designing, coaching, coordinating, facilitating, monitoring and evaluating behavior modification and competency base training programs.

Cassandra is also a Certified Addiction Professional, International Certified Addiction Counselor, Certified Relapse Prevention Specialist and a Certified Domestic Violence Facilitator and Assessor and Business and Life Coach. Cassandra has a Bachelor of Science degree in Professional Studies and a double Master’s degree in Human Resource Development and Administration from Barry University and a Master’s degree in Mental Health Counseling from Springfield College in Tampa, FL. She is a Licensed Mental Health Counselor. She served on the Domestic Violence Council of Palm Beach County and served on the Domestic Violence Fatality Review Board for two years. She is the co-founder of the Miracles Club, Inc., which opened its doors in 2001. The clubhouse serves the recovery community by providing 12 step recovery meetings and other community education programs to alcoholics, addicts and their family members.

She is married with two children, grandchildren and one great grandchild. Cassandra is committed to health and safety of the citizens of Florida and across the United States.


Kristin Szostak
Clinical Director

Kristin earned a Master of Arts Clinical & Counseling Psychology from LaSalle University and a Bachelor of Arts in Psychology from Rutgers University. Her professional career boasts work across the spectrum of care.

She has experience in leadership, administration, and direct care serving persons in medication assisted treatment programs, abstinence based programs, and a multitude of community agencies to collaborate in personalized and complete care. Kristin strives earnestly to develop and foster connections as she walks with individuals along their journey to achieve sobriety, recovery, and a full return to living.


Our Clinical Offices

1880 JFK Blvd, Suite 1110
Philadelphia, PA 19103