Matthew Hamilton, MD

Dr. Natalie Cummings is a board-certified adult psychiatrist, and board-eligible geriatric psychiatrist. She obtained her medical degree from the University of North Carolina at Chapel Hill, and completed her residency training in psychiatry at the University of Miami Miller School of Medicine and Jackson Memorial Hospital. She then went on to complete her geriatric psychiatry fellowship at Icahn School of Medicine at Mount Sinai Beth Israel. During her fellowship, Dr. Cummings participated in Mount Sinai's Visiting Doctors Program, providing patient-centered and compassionate care to homebound elder adults in New York City. She also received training at Coler Rehabilitation and Nursing Care Center on Roosevelt Island during her fellowship, and presented at the American Association for Geriatric Psychiatry annual meeting. During her training, Dr. Cummings gained extensive experience providing psychiatric care to various patient populations in multiple patient care settings, including in the outpatient clinic, inpatient unit, and emergency department. Following her training, Dr. Cummings worked at New York Presbyterian's Gracie Square Hospital, serving first in the position of float psychiatrist, providing care to patients on every inpatient psychiatric unit (including the young adult/college student program, Orthodox Jewish program, psychotic disorders program, crisis-stabilization program, dual focus program, and Asian Psychiatry program), before transitioning to an established psychiatric attending for the older adult program. During her time at Gracie Square Hospital, Dr. Cummings received the Physician of the Year Award, and served as a Clinical Assistant Professor of Psychiatry at Weill Cornell Medicine. She worked closely alongside staff psychologist, social workers and nurses to provide multidisciplinary, collaborative care to patients suffering from a variety of mental health conditions. Dr. Cummings primarily focuses on medication management and supportive psychotherapy, but has extensive training in utilizing various therapy modalities, including cognitive behavioral therapy, interpersonal therapy, reminiscence therapy, and psychodynamic psychotherapy. When appropriate, Dr. Cummings will refer for more extensive psychotherapy and/or collaborate with your established psychotherapist for comprehensive care. Dr. Cummings strongly believes that addressing psychosocial and interpersonal factors (including relationship health, economic stressors, social isolation and loneliness) is as essential as pharmacologic management in treating mental health conditions. She has particular experience and interest in treating older adults and those suffering from memory disorders, but provides treatment for a variety of psychiatric conditions including depression, anxiety, bipolar disorder, obsessive-compulsive disorders, trauma-related disorders and substance use disorders. Dr. Cummings is a member of the American Psychiatric Association and American Association for Geriatric Psychiatry.

Dr. John Lundeen earned his medical degree from the Medical College of Georgia and completed his psychiatry residency at TriStar Centennial Medical Center. He has worked with adults of all ages in both outpatient and inpatient settings, bringing a wide range of experience to his practice.

Dr. Lundeen approaches every patient with respect, empathy, and a genuine desire to understand their unique experience. He recognizes that seeking treatment can be intimidating and strives to create a welcoming, non-judgmental environment where patients feel safe and heard.

Dr. Lundeen believes in a collaborative treatment process, prioritizing each patient’s goals, values, and input. He emphasizes mental health education as a core component of care, empowering patients to better understand their treatment options and take an active role in their well-being.

Ms. Celeste Boyd is a dual board certified Psychiatric Mental Health and Family Nurse Practitioner.  She is the CEO and Founder of Metamorphosis Psyche, a psychiatric mental health resource platform.  She has practiced in family medicine since 2011 and psychiatric mental health medicine since 2013.  She has clinical experience and expertise in substance use disorders, addiction rehabilitation, sleep medicine, general psychiatry, and serious mental illness (SMI) in both private and public sectors.  In Academia, she has extended her knowledge and experience as Adjunct Clinical Faculty at School of Nursing Graduate Programs.

Since 2017, Ms. Boyd has been practicing general psychiatry in the outpatient private sector.  Ms. Boyd provides medication management and psychotherapy for acute, chronic, and comorbid psychiatric conditions that include Anxiety Disorders, Depression, Mood Disorders, ADHD, OCD, and PTSD.  Her clinical treatment modalities include supportive therapy, solution-focused therapy, motivational enhancement, mindfulness, and cognitive behavioral therapy.

As a clinician, she promotes mental health awareness to reduce stigmatization and empower those suffering and struggling with mental illness. Ms. Boyd clinical practices are oriented towards the Mental Health Recovery Model, which permits individuals to go through an active process of change, being in control, strengthening, and empowering themselves to improve their mental health and well-being.

Dr. Ethan Atwood is a board-certified psychiatrist. He earned his medical degree from the College of Medicine at the University of Arkansas for Medical Sciences. He completed his psychiatry residency and fellowship at the University of Alabama at Birmingham, and he completed a forensic fellowship at the University of Arkansas for Medical Sciences.

New patients can expect a warm and welcoming atmosphere when beginning their journey with Dr. Atwood. He emphasizes a holistic approach to mental health care, combining medication management with supportive therapies. His empathetic nature and commitment to patient well-being ensures a nurturing and supportive environment.

Dr. Atwood believes in a collaborative approach, working closely with his patients to develop treatment goals and adjust treatment strategies as needed. He is committed to providing ongoing support and guidance, ensuring that patients feel confident and supported throughout their mental health journey.

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Dr. Seth Flesher is double board-certified in adult psychiatry and addiction medicine.  Dr. Flesher’s practice focuses on medication management of psychiatric illness without the use of controlled substances.  Typically, he offers this in conjunction with supportive or emotionally focused therapy in 30-minute follow-up visits. However, occasionally Dr. Flesher may believe that additional therapy is also needed and ask that you bring a therapist into your care team to provide the best outcome.

Before joining Talkiatry Dr. Flesher was Medical Director of Advanced Psychiatric Services [complex/high profile cases] at Kings County Hospital and Unit Chief of the Covid19 positive unit.  He was also a clinical professor at Downstate Medical College where he was voted educator of the year numerous times by psychiatric residents and medical students.  Dr. Flesher is a graduate of the prestigious combined 6-year BS/MD program at The Sophie Davis School of Biomedical Education.  He did research at the neuropsychiatric branch of the National Institute of Mental Health, completed his psychiatric residency at St. Lukes/Roosevelt Hospital, and he received his master’s degree in public health from Columbia University.

Dr. Flesher believes that psychiatry should start with a thorough assessment to arrive at an accurate diagnosis.  Then a discussion with the patient of the different evidence-based options available.  Followed by shared decision-making to arrive at an effective treatment plan to achieve the goals that the patient identifies as being important.  This should be done in an honest, open, non-judgmental, but realistic environment.  Understanding that the ultimate goal is to get the patient to a position where they will no longer need medication and/or therapy.

Margaret Ngumi, MSN, APRN, FNP-C, PMHNP-BC, is a dual board-certified Psychiatric Mental Health and Family Nurse Practitioner with over 20 years of experience in healthcare. She began her career as a Family Nurse Practitioner and later pursued a post-master’s certification in psychiatry to address the growing need for accessible mental health services. Margaret has extensive experience in both inpatient and outpatient settings, treating conditions such as depression, anxiety, PTSD, mood disorders, and substance use disorders.

She takes a collaborative, patient-centered approach to care, creating a safe and supportive environment where individuals feel heard and empowered. With a strong emphasis on holistic care, Margaret considers all aspects of a patient’s well-being—including lifestyle, relationships, and overall health. Whether through medication management, therapy, or lifestyle modifications, she is committed to helping patients achieve meaningful and lasting improvements in their mental health.

Margaret begins with a comprehensive psychiatric evaluation to understand each patient’s history, concerns, and goals. She then works closely with them to develop a personalized care plan that may include medication, therapy, and evidence-based lifestyle interventions. She prioritizes open communication, patient education, and ongoing collaboration to ensure treatment remains effective and evolves with each patient’s needs. Through her compassionate and evidence-based approach, Margaret is dedicated to helping individuals find balance and improve their overall quality of life.

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