Vandana Kethini, MD

Background and credentials

Dr. Nilesh Tannu is a board-certified psychiatrist by the American Board of Psychiatry and Neurology. He earned his medical degree from B.J. Medical College in Pune and completed his adult psychiatry residency at the University of Texas Medical School at Houston, where he served as chief resident. During his training, he received awards from the Society of Biological Psychiatry, the American Academy of Addiction Psychiatry, and the American Psychiatric Institute for Research and Education. He has been practicing General Psychiatry and Consultation-Liaison Psychiatry for the past seven years at Texas Medical Center in Houston, Texas. Additionally, he has served as an assistant professor of psychiatry at the Texas Medical Center, working at UT Physicians Clinics and Memorial Hermann Hospital. He is also a member of the Editorial Board for BMC Genomics Journal.

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Treatment approach

Dr. Tannu follows the bio-psycho-social model to provide evidence-based psychopharmacologic treatment. He integrates supportive therapy and cognitive-behavioral therapy (CBT) modalities into his practice to create personalized and comprehensive treatment plans. He is committed to mental health care, education, and helping patients achieve optimal functioning in their personal and professional lives. His clinical expertise includes ADHD, anxiety disorders, depressive disorders, bipolar disorder, psychotic disorders, insomnia, eating disorders, and complex medical comorbidities.

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What you can expect in a first visit

During the first visit, patients can expect a comprehensive assessment where Dr. Tannu takes the time to understand their symptoms, treatment history, and personal goals. He employs a collaborative approach to develop a tailored treatment plan that may include medication management and therapy interventions. His focus is on evidence-based care, ensuring that patients receive treatments that are scientifically backed and aligned with their individual needs.

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Why Talkiatry?

We’re a virtual mental health practice that makes it easy to find great care. We combine quality and convenience to help you thrive—faster. Our providers, like this one, are highly trained experts who specialize in medication management and collaborate with you on a treatment plan that fits your needs and comfort level.

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Dr. Erica Mark is a board-certified psychiatrist with experience in both inpatient and outpatient care. She formerly served as a Staff Psychiatrist at a VA Medical Center, where she specialized in the mental health needs of veterans. Dr. Mark earned her B.S. in Biological Sciences, Summa Cum Laude, from Hampton University, received her MD from the University of Texas Medical Branch, and completed her psychiatry residency at Tulane University School of Medicine, serving as Chief Resident in 2017.

Dr. Mark fosters a warm, supportive environment where patients feel heard and respected. She values open communication and works collaboratively to set clear, personalized treatment goals. Deeply committed to service, she has supported underserved and marginalized communities through various nonprofit initiatives.

During initial sessions, Dr. Mark takes time to understand each patient’s history, concerns, and goals. She then creates individualized treatment plans aligned with each patient's unique needs and preferences. Dr. Mark encourages ongoing dialogue to adapt care plans and support long-term progress.

Dr. Kristin Ratz is a Board-Certified psychiatrist who is an expert in the diagnosis, treatment, and prevention of mental, emotional and behavioral disorders. She specializes in medication management combined with supportive therapy during 30-minute follow-up sessions. Dr. Ratz recognizes that each patient is unique and believes in an environment of collaboration, in which the patient and psychiatrist work together in order to develop the best individualized treatment plan. A California local, Dr. Ratz obtained her undergraduate education at University of California, Davis, graduating magna cum laude with a degree in Human Development. She then attended medical school at Loma Linda University School of Medicine, obtaining her Medical Doctorate. Following this, she completed her adult psychiatry residency training at the distinguished University of California, Irvine. Dr. Ratz has worked in a diverse range of healthcare settings, including county and community clinics, and is very experienced in telepsychiatry. She pays close attention to not only an individual's emotional state, but also their physical, spiritual, and social well-being, in order to provide her patients with exceptional holistic care.

Dr. Ariela Karasov completed her psychiatry residency at Stanford, serving as Chief Resident in her final year, and pursued a fellowship in Neuropsychiatry at Stanford Hospital. She is board certified in Behavioral Neurology and Neuropsychiatry and has worked as a National Expert in bipolar disorder at the VA. She has experience treating Generalized Anxiety Disorder, Obsessive-Compulsive Disorder, Bipolar Disorder, PTSD, and Depression, as well as patients with comorbid neurologic and mental health conditions. Dr. Karasov has also taught residents as adjunct clinical faculty at the University of Wisconsin Hospital and Clinics.

Dr. Karasov takes a collaborative approach, actively engaging patients in treatment planning and decision-making. She incorporates therapy into her practice, emphasizing each individual’s values and what gives their life meaning and purpose. Patients can expect a thoughtful, empathetic, and patient-centered environment where their goals and experiences are prioritized.

She values a thorough evaluation to understand how medical, psychological, and social factors contribute to a patient’s presentation. When appropriate, she invites family members or friends to provide collateral information to ensure a complete understanding, guiding a tailored and effective treatment plan.

Dr Marc Whaley is a Board Certified Psychiatrist in Adult Psychiatry, with extensive clinical experience over the past 50 years, mostly in outpatient treatment, and some in-patient settings, in addition to Forensic (legal) ones. He received his undergraduate degree at Johns Hopkins in Baltimore and his medical degree at Tufts Medical School in Boston, and then went on to train at Tufts New England Medical Center in Boston, for his psychiatry residency. He has held leadership roles, Chief of Department of Psychiatry in a community hospital, President of the local Psychiatric Chapter of the Massachusetts Psychiatric Society, and founder of a private group outpatient psychiatric practice on Cape Cod called The Psychiatric Collaborative. In 2018, he closed his private practice, seeking more free time in the later years. It did not take long, however, to get back to active practice, first by reviewing files for insurers around the issue of medical necessity, disability, and other psychiatric determinations. He got his first experience in Telepsychiatry when working remotely for a community hospital, far from his home, evaluating patients presenting to their busy ER; He experienced this as a practical and efficient way of delivering psychiatric services. When that contract ended after 3.5 years, he learned about and joined Talkiatry to work as a Staff Psychiatrist, in their well-organized comprehensive program. Dr. Whaley has been recognized by his peers for his career achievement, and he was the 2022 recipient of the Outstanding Psychiatrist Award for Clinical Psychiatry from the MA Psychiatric Society. He has also been a regular panel member, over the past 13 years, for a monthly NPR Radio Talk Show, ( WGBH Cape Cod affiliate, WCAI), The Point with Mindy Todd, focusing on multiple mental health topics.

Dr. Michael Gravenstein earned his medical degree from the University of Florida College of Medicine, where he also completed his psychiatry residency. During training, he was recognized with multiple awards, including the Malcom Randall VA Resident of the Year Award, the Ross A. McElroy Psychotherapy Award, and the John “J.D.” Dorian Award for best sense of humor. He has worked across outpatient, inpatient, and consult liaison settings, and has experience treating a wide range of conditions including depression, anxiety, ADHD, OCD, personality disorders, and transitional age concerns. He also has expertise working with LGBTQIA+ patients and provides psychodynamic, CBT, and supportive therapies.

Dr. Gravenstein believes in a comprehensive approach to treatment that integrates medications, therapy, and lifestyle interventions. While medications can be very effective, he views them as just one part of a broader treatment plan tailored to each patient’s needs. He emphasizes individualized care and sees treatment as a team effort, meeting patients where they are and progressing at a pace they feel ready for.

Dr. Gravenstein strives to create a warm, collaborative environment that fosters open communication and genuine connection. He may challenge patients therapeutically but always with careful attention to their readiness and comfort. His goal is to build trust so that meaningful conversations and progress can occur. For him, success is always shared—when patients succeed, they succeed together; when challenges arise, they regroup and move forward together.