Mark Sisti, PhD, ACT

Mark Sisti, PhD is the founder and director of Brooklyn & Suffolk Cognitive-Behavioral, PLLC. He is a graduate of Hofstra University, a licensed psychologist and a adjunct professor at Yeshiva— Ferkauf University, Department of Clinical Psychology. Dr. Sisti is a certified cognitive therapists and trainer within The Academy of Cognitive Therapy. He is also a peer reviewed trainer in a more contemporary experiential CBT called Acceptance and Commitment Therapy (ACT).  His advanced training in cognitive therapy was under the tutelage of a CBT master clinician, Robert Leahy, Ph.D., at The American Institute for Cognitive Therapy, where Dr. Sisti was formerly the associate director.

Dr. Sisti has extensive experience with anxiety disorders through his work at Freedom From Fear, a nationally recognized anxiety and mood disorder advocacy organization, where he was formerly the director of cognitive therapy and where he also participated as a certified cognitive therapist in research trials for N.Y.S. Psychiatric Institute & Columbia Presbyterian. He has also supervised doctoral interns from both Yeshiva-Ferkauf and Hofstra Universities and is an volunteer adjunct clinical supervisor for Yeshiva University Graduate School of Psychology. He trains various mental health experts and professionals in CBT, mindfulness based CBT’s, such as Acceptance and Commitment Therapy (ACT) and  has presented trainings and symposiums for the American Psychiatric Association, the American Psychological Association, Association for Contextual Behavior Therapy and Suffolk County Psych Assoc.  He has also given numerous seminars and trainings on Acceptance and Commitment Therapy (ACT) and other mindfulness based CBT’s. Dr. Sisti is also a published author on cognitive therapy, mindfulness, ACT, and Compassion Based Therapy, and Functional Analytic Therapy (FAP).

As a committed life long learner, and in an ongoing effort to keep up with state of the art CBT and its newest developments, he has committed himself and his staff to ongoing supervision and training in, “third generation” CBT’s and mindfulness informed CBT, e.g., DBT, FAP, Compassion Informed Therapy and ACT.  He has extensive training and experience with Acceptance and Commitment Therapy (ACT) through its founders and leaders, Dr. Steven Hayes & Kelly Wilson. Additional ACT experience comes through being a past president of the NYC chapter of ACBS (Association of Contextual Behavioral Science) ACBS-NYC, and founder of Long Island ACBS, a local ACT affiliate, ACT training and peer study group. He has also trained repeatedly with master third generation clinicians such as; (DBT)Dr. Marsha Linehan & Compassion Focused Therapists (Dennis Tirch, & Tara Brach & Christine Neff/Chris Germer). He has also trained and given trainings in “interpersonal” CBT’s such as Functional Analytic Psychotherapy with Dr.’s Mavis Tsai & Bob Kohlenberg, along with completing a one year relational psychoanalytic training at the Mitchell Institute for Relational Psychoanalysis. He is also founder & president of The “Long Island-CBT Network (”, a LI based professional CBT/EBP networking & dissemination organization as well as being on the board of Suffolk County Psych Association.  Dr Sisti, also incorporates the mindfulness insights he has garnered as a life long practitioner of TM (Transcendental Meditation), Ashtanga Yoga, and Aikido 1st Dan into his life and work.

Maria Steblai, Psy.D.
Maria Steblai, PsyD., is a senior founding member of Suffolk Cognitive Behavioral beginning in 2004. Dr. Steblai’s long tenure at our center has made many patients and their families consider her a life long mental health resource. She obtained her doctorate from Hofstra University, where she graduated Phi Beta Kappa. Dr. Steblai obtained her initial clinical training in cognitive-behavioral therapy at Hofstra University.

Her clinical experience at North Shore University Hospital has given her invaluable expertise working with the most intense of crises in peoples lives and the opportunity to work as a team with medical/psychiatric professionals. Additionally her ongoing experience working as a certified school psychologist within several Long Island School districts, gives her broad experience with both children, adolescents, adults and families. We are very fortunate to have a professional with this much experience with childhood and adolescent disorders on staff. Her specialties include, cognitive-behavioral Therapy, ADHD, eating & body image disorders, and children-adolescent disorders. She has presented her research at psychological conventions on; attention & hyperactivity disorders (ADD & ADHD), eating disorders and body image disorders. She regularly conducts groups, workshops and seminars on ADHD, eating disorders and adolescent trauma.

Denise Coscia, PhD

WP_20151213_09_26_00_Pro - Version 2Denise Coscia, PhD., received her doctoral degree with Psi Chi honors at Hofstra University in 2007. Hofstra’s doctoral training program is cognitive-behavioral and therefore has prepared Dr. Coscia well for helping our patients to understand their strengths and weakness in cognitive behavioral terms.

Her time at North Shore LIJ, provided a wide range of experience with psychological testing, evaluation and research, as well expertise in doing cognitive-behavioral assessments and diagnosis, and is therefore a major asset here at Suffolk Cognitive Behavioral. She had previously gained additional CBT expertise at The Bleuler Psychotherapy Group where she worked with a diverse range of, children, adolescents and adults presenting a full range of problems, e.g., from ADHD, to mood disorders to anxiety, phobias, and relationship problems. She has also developed CBT skills working individuals with more severe problems due to her valuable time interning at Brunswick Hospital Inpatient Psychiatric Unit and volunteering at Payne Whitney Cornell Medical Center. Further broadening her range of skills, she interned at both the elementary and high school levels , giving her the opportunity to develop insight and skills for helping the developing adolescent. Dr. Coscia’s experience working with aging populations and geriatrics has provided extensive experience and empathy for the challenges of growing older, something more and more American baby boomers are going to have to face and learn to thrive in. This full range of developmental experience has also provided Dr. Coscia with an understanding of adult family dynamics and the challenges of adults caring for aging parents and children.

All in all, we are very proud of the full range of life experience and CBT background Dr. Denise Coscia brings to Suffolk Cognitive Behavioral, as well as the deep care and empathy she has cultivated while working with both the challenges of adolescence, emerging adulthood, middle age, as well aging adults.

Rachel Klechevsky, LMSW

Rachel Klechevsky received her Masters of Social Work from NYU and her Masters of Human Sexuality Education from Widener University.  She has practiced psychotherapy since 2012, using a variety of comprehensive approaches including CBT based narrative therapy and third generation CBT based existential therapy.  These varied skills coupled with her experience with grief work and relationship difficulties, make Rachel an excellent choice for clients who are also struggling with grief, depression, anxiety disorders (panic, phobias, PTSD, etc), as well as other mood disorders.

Rachel also has a specialty in sex therapy and sexuality.  She has a special interest in working with relationships, whether straight, LGBTQ and/or non-monogamous and with individuals or couples who are dealing with sexual dysfunction, sexual identity concerns and/or general relationship stresses.



Shelli Trager – Intake Coordinator
Ms. Trager is the intake coordinator at Suffolk Cognitive-Behavioral, she is often the first person to meet and greet patients who call the center for information. With a call to the center, she will be more than happy to answer any general questions about the center. Ms. Trager has worked for mental health professionals and their patients for decades and has in that way gathered a wealth of invaluable experience in helping patients to make difficult decisions around starting therapy and answering general mental health FAQ’s (frequently asked questions). Ms. Trager also manages the calendars and appointments of our staff, and will patiently guide patients through the complex process of initial screening and referral.

In addition, to her work at SCB, Ms. Trager is an entrepreneur, with a BS in Education, from The University of Connecticut. She manages her own multi-faceted medical business by helping other mental health professionals with all aspects of office management, information Technology, etc.


Contact us to make your next appointment today or call us at:
Long Island Offices - 631–696-2896
Brooklyn Offices - 347-687-6353


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