Marnie Stefan, MD

Dr. Corey Greenwald is a board-certified psychiatrist with years of experience treating patients in both acute inpatient psychiatric emergencies and outpatient medication and psychotherapy settings. He earned his medical degree from Brown University, completed his internship in the Columbia system, and pursued residency training at Mount Sinai Medical Center in New York City. Dr. Greenwald has practiced in academic, urban, suburban, and rural environments, which has given him broad perspective and adaptability in caring for diverse patient populations.

Dr. Greenwald emphasizes psychoeducation as a core part of care, ensuring patients are active participants in understanding and managing their mental health. He brings a deep interest in transcultural issues and in how social media and news cycles impact emotional well-being. Having witnessed the effects of mental illness within his own family, Dr. Greenwald approaches his work with empathy, insight, and a strong commitment to helping patients feel supported throughout their journey.

Dr. Greenwald works collaboratively with patients to define or clarify concrete treatment goals by the end of the initial appointment. He maintains a low threshold for revisiting and adjusting treatment plans if progress feels unsatisfactory, ensuring care remains flexible and effective. His informal, eclectic interpersonal style allows him to tailor his approach to each individual, fostering trust and partnership in the therapeutic process.

Dr. Rachel Bennett is a double board-certified physician in General Adult and Child and Adolescent Psychiatry.  She graduated magna cum laude from Rosemont College, earning a Bachelor of Arts degree in Biology with dual minors in Biochemistry and English Literature.  She earned her medical degree from Drexel University College of Medicine with a concentration in Medical Humanities.  Dr. Bennett completed residency training at the Hospital of the University of Pennsylvania and a Child and Adolescent Psychiatry Fellowship at the Children’s Hospital of Philadelphia.  Her areas of research interest and publication during undergraduate and medical study and training have included pediatric palliative care, caregiver burden, autism spectrum disorders, and attachment-based family therapy.

Before joining Talkiatry, Dr. Bennett worked for nearly 12 years as a staff psychiatrist for Prospect Crozer Keystone Health System.  Her extensive clinical experience includes providing in-person and telepsychiatric care in a variety of settings including outpatient psychotherapy and community mental healthcare practices, hospital-based clinics, and school-based treatment programs, as well as emergency, consultation-liaison, and inpatient psychiatry.

Dr. Bennett’s treatment approach features an appreciation of the power of narrative in pursuit of deep self-understanding and meaningful personal progress.  She offers thorough assessment in an approachable, warm, and authentic manner, emphasizing the importance of lifestyle factors, the mind-body connection, relationships, and therapeutic rapport in collaboratively empowering her patients to achieve positive change, recovery, and resilience.  She has training and experience in a wide range of therapeutic modalities, including supportive, psychodynamic, cognitive-behavioral, and family psychotherapy as well as positive psychology, and Dr. Bennett’s strong systems-oriented perspective facilitates her provision of evidence-based care both as an individual psychiatrist and in collaboration with specialized medical and therapeutic care providers when appropriate.

Dr. Zac Keller, DO, DABPN (he/his), is a board-certified psychiatrist with experience across inpatient and outpatient settings. He has held leadership roles including Interim Medical Director and Director at Richard Young Hospital, where he also created and led the hospital’s ECT program. Dr. Keller’s clinical focus includes ADHD, PTSD, and personality disorders, and he brings an integrative lens to psychiatric care.

Dr. Keller takes a collaborative, supportive, and evidence-based approach to treatment. He values confidentiality, culturally sensitive care, and trauma-informed practice. Known for his warm yet direct communication style, he works to create a respectful, nonjudgmental environment where patients feel heard, understood, and actively involved in their care.

Care begins with a comprehensive intake that explores medical, psychiatric, social, and functional aspects of a patient’s life. Session length and frequency are tailored to individual needs. Treatment plans are developed collaboratively and may include medication management combined with talk therapy and other evidence-based interventions. Progress is reviewed regularly and adjusted based on ongoing dialogue.

Dr. Jacobs is board-certified in Adult Psychiatry by the American Board of Psychiatry and Neurology. She specializes in medication management for adult patients across a range of psychiatric conditions, with a focus on treating depression, anxiety, bipolar disorders, and ADHD. Dr. Jacobs employs a therapeutic approach to medication management, incorporating supportive and psychodynamic psychotherapies into her sessions. She selects psychopharmacological treatments and therapies tailored to each patient's individual needs and symptoms. Dr. Jacobs earned her Bachelor of Science in Science and Business from the University of Notre Dame. She graduated from medical school at the University of Mississippi, where she was honored with membership in the Gold Humanism Honor Society for her exceptional clinical skills, interpersonal abilities, and dedication to patient care. She then returned to Texas to follow her passion for mental health, completing her residency in Psychiatry at the University of Texas Southwestern Medical Center. Dr. Jacobs developed a strong enthusiasm for enhancing mental health care within communities and completed a fellowship in Community Psychiatry through the UT Southwestern Altshuler Center for Education and Research in the Dallas-Fort Worth area. Over the years, she has worked with major community mental health organizations across Texas and has recently focused on leveraging telemedicine to coordinate mental health support with primary care providers. Throughout her career, Dr. Jacobs has been committed to psychiatric research, educational initiatives, and organizational efforts to advance mental health care education and patient care in communities. She is an active member and leader in several medical and psychiatric organizations. Dr. Jacobs takes great pleasure in connecting with patients via telemedicine, focusing on meeting them where they are in their mental health journey and supporting their needs and goals.

Dr. Iris Guerrero Urena is double board-certified in psychiatry and consultation-liaison psychiatry. She received her medical degree from Universidad Iberoamericana in the Dominican Republic and went on to complete psychiatric residency at Lincoln Hospital in New York City. Dr. Guerrero then completed a consultation liaison fellowship at Morningside and West Mount Sinai Hospital in New York, further acquiring proficiency in caring for patients with complex medical and psychiatric comorbidities. After completing training, Dr. Guerrero worked in an acute inpatient unit and as a psychiatric consultant for patients admitted to medical units in Oregon. Dr. Guerrero Urena focuses on medication management while also implementing elements of supportive, dialectical behavioral, and cognitive behavioral therapy within each session to fully address individual needs. At times, Dr. Guerrero Urena may recommend a therapist for additional therapy. Dr. Guerrero Urena is experienced in treating a wide range of psychiatric conditions including depression, bipolar disorder, anxiety, PTSD, OCD.

Dr. Krista Alexander is a board-certified psychiatrist who loves equipping her fellow human beings to feel and function better. She studied medicine at the University of Texas Southwestern Medical School and completed her residency at Duke University. She has worked in both private practice and integrated primary care/behavioral health care settings. She is a member of the American Psychiatric Association and the North Carolina Psychiatric Association. Krista offers medication management and supportive psychotherapy for mood disorders, anxiety disorders, trauma, ADHD, substance use disorders, and other mental health issues. She strives to embody "relational prescribing” and believes that med management is most effective in the context of a relationship of mutual trust, emotional safety, and shared decision-making between provider and patient. She has trained in psychodynamic psychotherapy and various forms of cognitive behavioral therapy, and tailors her approach to each patient's individual strengths and needs. Krista understands that the needs of the whole person must be addressed in order to facilitate growth and healing. She enjoys collaborating with fellow medical/mental health providers to address a patient's complex needs as an integrated team.