LOGOMain Number: 301-982-3437 Greenbelt, MD Direct: 301-969-4090
Olney, MD Direct: 301-969-4060
Frederick, MD Direct: 301-245-6300


Psychiatric Nurse Practitioners:

Psychiatric Physician Assistants:


Ahmed Hefuna, MD

Greenbelt, Olney
  • Board Certified General Psychiatry
  • Board Certified Child and Adolescent Psychiatry
  • General Psychiatry Residency at Albert Einstein Medical
  • Center Philadelphia
  • Fellowship in Child Psychiatry Children National Medical Center
  • Medical School Cairo University Faculty of Medicine Cairo , Egypt
Assistant Professor of Child Psychiatry at Georgetown University/ Medical director of inpatient Child Unit at Adventist Behavioral Health, Supervising Training and education of Child Psychiatry Fellows and Medical Students at Georgetown University Attending Psychiatrist at Albert Einstein Medical Center , Outpatient clinic/ Developmental Disorder Clinic/ Partial Hospital & IOP Joined Private Practice in 2015
Areas of interest
Mood disorders Developmental disorders Trauma and PTSD
Languages spoken
English, Arabic

Joshua Sussal MD

Child Adolescent and General Psychiatrist
Greenbelt, Olney, Frederick
  • Board Certified General Psychiatry
  • Board Certified Child and Adolescent Psychiatry
  • Medical Degree from Ross University School of Medicine
  • General psychiatric residency at Stony Brook University, New York
  • focused in crisis management
  • Child and Adolescent Fellowship Children's National Medical Center, Washington DC
  • Worked at a Comprehensive Psychiatric Emergency Program (CPEP)
  • Diverse experience with:
    • Troubled youth
    • Dementia
    • Depression
    • Chronic mental illness
    • Detoxification
    • Co- morbid medical conditions
Residency trained in:
  • Psychodynamic, cognitive and family centered therapies in adults, adolescents and children Concentrated area in neurology / genetics
  • Five years of experience with Dimensions Health System Directing their Partial Hospitalization Program
  • Co-directed the consult and adult inpatient unit at Laurel Regional Hospital.
Entered private practice in 2011. Programs introduced to his private practice:
  • In home services for youths
  • Transcranial Magnetic Stimulation (TMS)
  • Court ordered evaluations for Department of Juvenile Services civil and criminal expert testimony pertaining to adults and children in a wide range of scenarios
  • Individualized Education Program (IEP)
  • Adoption/ foster placement
  • Most criminal matters
  • Independent Medical Evaluations
  • Detoxification
  • Medication management
"I enjoy public speaking and educating both privately and in the community to promote mental health awareness."

Todd Christiansen, MD

Child Adolescent and General Psychiatrist
Todd.Christiansen@sussalpsi.com Staff
  • Board certified child, adolescent, and adult psychiatrist
  • Practice is both child and family centered when working with children and adolescents
  • Medical Degree from the Medical College of Wisconsin
  • General psychiatry residency at the University of Wisconsin
  • Child and adolescent psychiatry fellowship University of Maryland
  • Forensic psychiatry fellowship University of Maryland
  • Department of Health as a consultant to the D.C. Superior Court
  • Family Court and also as the Associate Chief Clinical Officer
  • Medical director for child and adolescent services at the
  • Psychiatric Institute of Washington
  • Attending physician on the inpatient child
  • Psychiatric staff member of the adolescent unit
Entered private practice with Dr. Sussal in 2012 and provides:
  • Direct treatment services and consultation
  • Court ordered evaluations
  • Custody evaluations
  • Forensic evaluations with expertise in
    • Civil
    • Criminal
    • Juvenile justice cases
  • Assessments and evaluations for Individualized Education Program (IEP)
  • Direct treatment provider in School mental health programs

Maria Hammill, MD

Maria.Hammill@sussalpsi.com Staff
  • Medical Degree University of the Philippines
  • Residency Medical College of Virginia/Virginia Commonwealth University
  • Fellowship in Child Psychiatry Johns Hopkins Medicine
  • Has acquired Board Certification in both Adult and Child Psychiatry

Dr. Hammill has been in outpatient private practice in adult and child psychiatry in Greenbelt since 1995. She believes in working closely with other physicians, therapists, psychologists, schools and other community agencies if it will help promote the treatment and well-being of patients and their families. Her patients come from all over Maryland when she used to be a consultant for different agencies and clinics and they have continued to follow her. Other physicians depend on her education, experience and expertise to provide second opinions and recommendations for treatment and educational placement. She sees children, adolescents and adults with mood disorders (anxiety, phobias, obsessive-compulsive disorders, depression and bipolar disorders), autism, learning disorders and attention deficit hyperactivity disorders and other psychiatric disorders with co-occurring medical conditions. She believes in providing comprehensive treatment to all her patients through medications and the different types of therapy.


Carolyn Clark, FPMHNP

Nurse Practitioner
carolyn.clark@sussalpsi.com Staff
  • Bachelor of Science in Nursing from Georgetown University, Washington DC
  • Master of Science in Nursing with specialty in Family Psychiatric Mental Health Nurse Practitioner from University of Maryland, Baltimore
  • Diagnosis and psychiatric evaluation
  • Medication management
  • TMS
  • Carolyn has experience working with children and adolescents diagnosed with psychiatric conditions in the inpatient setting at Children's National Medical Center in Washington DC. She has worked closely with children and adolescents diagnosed with autism, ODD, ADD, depression, and a host of other childhood psychiatric disorders. She is a certified Family Psychiatric and Mental Health Nurse Practitioner and has training to serve clients across the lifespan, including adults. Since joining this practice in 2013, Carolyn has helped hundreds of adults suffering from psychiatric disorders such anxiety, depression, bipolar disorder and schizophrenia to manage their symptoms through medication and lifestyle interventions.

Carolyn focuses on an integrative approach to treating psychiatric disorders, incorporating elements of mindfulness, nutrition and exercise into her treatment recommendations.


Lynda Artusio, CRNP-PMH

Nurse Practitioner
lynda.artusio@sussalpsi.com Staff
  • Lynda Artusio is a board certified registered nurse practitioner in psychiatric mental health (CRNP-PMH). She is also a board certified clinical nurse specialist in psychiatric mental health (CNS-PMH). Lynda is licensed through the Maryland Board of Nursing as a psychotherapist and as a psychiatric medication provider for children, adolescents and adults of all ages. She graduated from Marymount University and the University of Maryland School of Nursing. Lynda has worked in a variety of mental health settings and as a nursing instructor at Frederick Community College. She has lived in Frederick for 27 years.

Kerin Hamilton, PA-C

Physician Assistant
kerin.hamilton@sussalpsi.com Staff
    I am a licensed and certified Physician Assistant with a Bachelor of Science Degree in Biology, a track in Education, and a Minor in Health from Salisbury University.
    Originally from Long Island, New York, I began my professional career here in Maryland and worked for four wonderful years as a high school educator. In addition, I spent summers teaching swim lessons and serving as a Red Cross volunteer. After personal reflection and recognizing my underlying passion for medicine; I changed my career focus and in 2013 completed my Masters of Science degree in Physician Assistant Studies from Towson University. My extensive PA training included clinical rotations in pediatrics, family medicine, internal medicine, emergency medicine, and various other specialties to become a well-rounded healthcare provider. Prior to starting here at Greater Washington Psychiatry and Counseling I worked as a PA-C in orthopedics. After joining GWPC in 2016, I am excited to pursue my longtime interest in mental health, psychiatry, psychology, psychotherapy, and psychopharmacology for children and adults. My goal is to help make a difference for my patients and their families, as I believe having a Healthy mind is the foundation to overall health and wellness.

Dominique Clark, PA-C

Physician Assistant
dominique.clark@sussalpsi.com Staff
    Dominique was born in San Diego, California and moved to Maryland when she was a teenager. She obtained her undergraduate degree in biology pre-med from Virginia Commonwealth University. She then worked at the National Institutes of Health in malarial research as a research assistant. Her tenure at NIH was wonderful but she left pursuing her master’s degree in physician assistant studies from Rutgers University.
Since graduating she has been fortunate enough to work in Physical Medicine and Rehabilitation and most recently psychiatry.

She has always had a passion for mental health, addiction medicine and infectious disease. Her mother has been a social worker for three decades, working with the mental health and HIV population. This led to her vigor to assist patients with mental health and their families lead more productive and autonomous lifestyles, as well as promoting mental health through service, advocacy and education. Her services involve psychiatric consultation, prescribing and managing medication, and proven effective forms of treatment such as TMS and Brainsway.

In her spare time, she enjoys horse back riding, swimming, shopping and spending time with her family.

Amy Zawatsky, LCPC

Frederick, Greenbelt, Olney
Amy.Zawatsky@sussalpsi.com Staff
  • Licensed Clinical Professional Counselor (L.C.P.C.)
  • Master's Degree in Mental Health Counseling from Rollins College, Winter Park, FL.
  • Post-graduate certification in Object Relations Theory and Practice from the International Psychotherapy Institute, Washington, D.C.

Amy joined the practice in 2013 and works with teens through late adulthood. She utilizes a combination of approaches to enhance an individual’s strengths, regain a sense of control and facilitate greater self-awareness. The most important aspect of her work is to create a safe, positive environment where her clients feel valued and understood.

Amy has a broad background bringing relief to clients with anxiety, depression, loss and/or death of a loved one, sexual identity and relationship/interpersonal challenges. She has worked with adjudicated female youth in both individual and group settings, young adults in college settings and middle-aged men and women coping with career and family transitions.


Christina Poff, LCPC

christina.poff@sussalpsi.com Staff
  • Licensed Clinical Professional Counselor (LCPC)
  • Approved Clinical Supervisor (ACS)
  • Master’s Degree in Professional Counseling from Liberty University

Staring her career path in 1997, Christina brings her expertise of working skillfully with individuals in their teens through late adulthood, assisting them in their quest for health and happiness.

She utilizes a variety of theories and techniques to address the unique, individual needs of her clients.

Christina works to create a therapeutic environment that is warm, trusting, compassionate, enlightening, motivating and optimistic.

Christina has proven to work effectively with those suffering with substance abuse and / or other addictions, dual diagnosis, LGBTQI / sexual identity related issues, depression, anxiety, stress management, interpersonal relationship problems, grief / loss & spirituality issues.

Prior to coming to GWPC, Christina worked as an Advanced Mental Health Professional Counselor in the field of public safety and corrections.

  • Substance Abuse / Addictions
  • Dual Diagnosis
  • LGBTQI / Sexual identity related issues
  • Spirituality / Personal identity struggles
  • Depression
  • Stress Management
  • Anxiety
  • Interpersonal relationship problems

Gena M Harmon, LCPC

Gena.Harmon@sussalpsi.com Staff
  • Master's Degree in Counseling from Western Connecticut State University
  • Advanced Graduate Certificate from Johns Hopkins University with a concentration in the counseling of families and children
  • Worked with people diagnosed with severe mental illness
  • Provided individual and group therapy to women suffering from physical and sexual abuse
  • Therapist at Johns Hopkins Hospital providing therapy to children and their families
  • Part of an innovative program between the Baltimore City school system and Johns Hopkins Hospital
  • Helped develop a partnership between the Baltimore City Police Department and therapists at Johns Hopkins
  • Performed psychological evaluations for several years at what is now Baltimore-Washington Medical Center
  • In private practice for the past twelve years providing counseling to adults, children and families
Ms. Harmon accepts patients between the ages of four and sixty-five.

Jacqueline Trombley, LCSW-C

Jacqueline.Trombley@sussalpsi.com Staff

I received my BA in psychology from University of Maryland College Park and a Masters in Social Work from University of Maryland School of Social Work Baltimore. I am a Licensed Certified Social Worker with a clinical focus and a board approved supervisor in the state of Maryland. I am a straight-forward and down-to-earth counselor with a genuine passion for the work that I do.

I am familiar with many of the popular treatment approaches such as CBT, DBT, and Solution-Focused Therapy, etc. but do not subscribe to the idea that one size fits all.

I tend to take an strengths-based and collaborative approach with my clients so that together we can find out what approach will best help them reach their treatment goals. I specialize in trauma and helping clients manage the subsequent symptoms such as anxiety, depression, grief, low self-esteem and others. I have received advance trauma training from the Lisa Firentz institute in Baltimore. I have worked with child welfare, therapeutic foster care, and have run several groups for teens in the Montgomery County school system. The most recent group I have run was the SPARCS (Structured Psychotherapy for Adolescents Responding to Chronic Stress) evidence-based group model. I work with adolescents, adults, individuals and families.

My aim is to be direct and clear so that you can determine if we are a good fit, as I believe some people do not continue therapy because they simply have not found the therapist who is the right fit for them. I encourage potential and current clients to always prioritize wellness and make your pursuit of joy your top priority.

  • 301-982-3437 ext. 391

Larry Harper, LCSW-C BCD

larry.harper@sussalpsi.com Staff
  • Education: MSW, University of Maryland, 1976
  • Board Certified Diplomat
  • Started Harper & Associates in 1976
  • Practicing since 1976
  • Works Mondays and Tuesdays 8:00am-7:00pm, Wednesdays 12:00pm-7:00pm and Thursdays 8:00am-5:00pm
Works With:
  • Young Children
  • Children
  • Adolescents
  • Adults
  • Substance Abuse
  • Family Violence
  • Mental/Emotional
  • Behavioral Dysfunction
  • Learning Disorders
  • Sexual Dysfunction
  • EMDR (Eye Movement Desensitization and Reprocessing)
  • Performs Conner’s test

Linda Campbell, LCPC

Linda.Campbell@sussalpsi.com Staff
  • Licensed Clinical Professional Counselor (LCPC)
  • Fifteen years experience working with:
  • Individuals
  • Couples
Specializes in counseling couples experiencing:
  • Difficult life situations helping them to:
    • Improve communication
    • Reduce relationship stress
    • Increase personal happiness and relationship satisfaction
Counsels individual adults experiencing:
  • Stressful life circumstances
  • Times of transition
  • Loss and grieving issues
  • Marital conflict
  • Depression
  • Phobias and anxiety

Lynn Sorberllo, LCSW-C

lynn.sorbello@sussalpsi.com Staff
  • Education: MSW, University of Maryland, 1991
  • Practicing Since: 1991
  • Works Mondays 1:00pm-5:00pm, Tuesdays 8:00am-12:00pm, Wednesdays 8:00am-8:00pm, Thursdays 8:00am-5:00pm and Fridays 8:00am-12:00pm
Works with:
  • Children (4 and up)
  • Adolescents
  • Adults
  • Mental
  • Emotional
  • Parenting Skills
  • Couples Counseling
  • Family Issues
  • ADHD
  • Learning Disabilities
  • Stress Management
  • Coping with Depression

Maureen Mann Ritz, LCPC

Maureen.Ritz@sussalpsi.com Staff
  • Licensed Clinical Professional Counselor (L.C.P.C.)
  • National Board Certified Counselor (N.C.C.)
  • Bachelor of Science in Psychology at Georgetown University
  • Master of Arts in Psychology from Catholic University

Ms. Ritz began seeing clients in various settings in 1982, beginning in hospital settings, then moving to a job as director of a community based mental health center (Olney Youth Services) in Montgomery County, Maryland,

which was funded by the State of Maryland, Department of Juvenile Justice, through the GUIDE program. She continued to work for the GUIDE program in various community based settings for more than 20 years, ending her association with GUIDE as the Chair of the Board of Directors. During her time with GUIDE, she conducted individual, group, family and couples sessions. She developed prevention and early intervention activities for schools and communities. The Olney community/Gazette newspapers awarded her the Citizen of the Year award in 1986 for her work with the adolescents and families of Olney. Also under the GUIDE umbrella, she worked on other part time contracts, including conducting pre-court evaluations of adolescents and adults, appearing as an expert witness in court and supervision of masters level counselors. Mrs. Ritz moved to counseling in school settings in the early 1990's, working as a Counselor in the Department of Health Education services at Georgetown University where she also founded and directed the program for students facing unplanned pregnancy. She then worked as the Counselor for three Elementary Schools, all part time. From there she became Director of Guidance and Counseling at DeMatha Catholic High School, a position where she is currently, and has been since 2001. Mrs. Ritz has been with the Greenbelt practice of Dr. Sussal since 2007, working part time evenings and Saturday's


Nicole Twaalfhoven, LCPC

Licensed Clinical Professional Counselor
nicole@sussalpsi.com Staff
  • Education: Master’s Degree in Clinical Mental Health Counseling from Johns Hopkins University and Master’s Degree in Childhood Development from The George Washington University.
  • Certified Fitness and Nutrition Specialist

I’ve started my career as a childhood development specialist and family counselor, during which I really understood how important safety and attachment are. In my sessions, I strive to understand the learning-style of the person or people sitting across from me, and working on improving habits, feelings, and behavior in a way that supports their lifestyle.

I work with adults of all ages, teens, and children under 14 years old accompanied by their caregiver. My therapeutic approach strongly focuses on how our thoughts and behaviors influence each other (CBT). This helps us understand how to process and cope with symptoms.

Languages Spoken
  • English, Dutch, German

Stanley Karanja, LCPC

Stanley.Karanja@sussalpsi.com Staff

Stanley Karanja is a family counselor who delights in working with preteens, adolescents, couples, adults and families. Stanley holds a MS degree in Counseling from Loyola University Maryland. Since his graduation in 2008 he has worked in various agencies in the mental health industry, gaining dynamic experience including behavior modification, conflict resolution, and coping with mental health challenges including:

  • ADHD
  • Anxiety
  • Depression
  • Life Transition
  • Oppositional Defiance
  • PTSD
  • Separation and Divorce
  • Grief and Loss

Stanley utilizes a strength-based approach to facilitate his clients to identify and confront the issues that tend to hinder them. His background in Education and Ministry has equipped him with ample skills that provide ease when working with his clients. Stanley will utilize CBT strategies, Family Systems Therapy and other treatment models to enable his clients to gain coping skills and abilities to manage their mental health challenges so as to lead full and resourceful lives.


Stephanie Arant, LCPC

Stephanie.Arant@sussalpsi.com Staff

Stephanie, a Montgomery County, MD native, joined the practice as a part-time therapist in April 2017, her day-job being the senior therapist for children and their families at a local middle school. Stephanie felt an immediate connection to her role as a psychotherapist, as she was able to combine her passion for the field, plus her practical experience, and became full time in July 2017. Stephanie's therapeutic style includes facets of cognitive-behavioral therapy (CBT), and she

incorporates a variety of additional techniques based on her clients' individual needs, including writing, drawing, play therapy, mindfulness and strengths-base approaches.

Using active conversation and encouragement, Stephanie’s collaborative, client-centered approach helps her clients gain of sense of their own individuality and uniqueness. Her warmth and support helps to create a safe, trusting environment where her clients can work on decreasing anxiety, increasing self-esteem, and feel more connected to themselves, others and the world.

  • Masters Degree in Mental Health Counseling from The Johns Hopkins University, Baltimore, MD
  • Bachelors Degree in Psychology from Hood College, Frederick, MD
  • Provides psychotherapy to elementary school-age children, adolescents and adults
  • (301) 969-4060 ext. 390

Steve Simon, LCSW-C

stephen.simon@sussalpsi.com Staff
  • Education: Masters, University of Maryland-Baltimore-2002; Masters in Psychology, Hood College- 1999
  • Works Mondays thru Wednesday 6:00pm-9:00pm and some Saturday mornings
Works With:
  • At Risk Youth
  • ADHD
  • Couples Therapy
  • Teens ages 13 and up
  • Drug and Alcohol Issues
  • Depression
  • Anxiety

Wendy Yowell, LCPC

wendy.yowell@sussalpsi.com Staff
  • Education: Master’s Degree in Clinical Counseling with an emphasis in CBT from Auburn University, 1997
  • Licensed Clinical Professional Counselor
  • Certified Clinical Trauma Professional
  • Youth and Adult Mental Health First Aid trainer

I am a counselor with 20 years of experience in a variety of settings. I began my career working with dual diagnosis clients within the public mental health systems of Alabama and Virginia. My private practice experience includes 15 years with the practice of Dr. Marnell, Dr. Hammill, and Dr. Sussal. In 2015, I established an intensive outpatient program for the treatment of trauma and substance use disorders. I presently work for the State of Maryland in the areas of dual diagnosis treatment, suicide prevention and trauma.

I am trained in cognitive therapy, mindfulness based practices and trauma informed care. My philosophy about counseling is that it is a collaborative relationship in which it is my privilege to partner with you in finding your way towards health and recovery.