Our Staff

Before joining Waltham Behavioral Health, LLC, Ms. Tsavoussis was a Psychiatric Clinical Nurse Specialist in private practice in Newton, at Greater Lowell Psychiatric Associates, Nova Psychiatric, Neurobehavioral Associates, and Neponset Health Center. Ms. Tsavoussis has been double-boarded in as a primary care Nurse Practitioner, and a Psychiatric Clinical Nurse Specialist and divided her time between primary care and psychopharmacology at Neponset Health Center until 2008. Prior to that, Ms. Tsavoussis was owner and CEO of Bayside Nursing Placement. Eleftheria Tsavoussis received her Post-Master’s Certification as Psychiatric Clinical Nurse Specialist from Boston College and a Master of Science from Simmons College. She received her bachelor’s degree in nursing from Boston College. She currently is an Adjunct Assistant Professor at UMass Lowell and has held teaching positions with Boston College and Simmons College. Ms. Tsavaoussis is a certified Psychiatric Clinical Nurse Specialist by the American Nurse Credentialing Center. She is a member of the Massachusetts Coalition of Nurse Practitioners and serves on the Massachusetts Action Coalition working to remove restrictions that limit patients’ access to high-quality, cost effective health care across a variety of specialties including primary care, psychiatric and mental health care, and pediatrics where patient care needs exceed physician supply. Ms. Tsavoussis was a contributing author to the MA Action Coalition Report: The Advanced Practice Nurse in Massachusetts. 

In addition to her work with Waltham Behavioral Health, LLC, Ms. Brennan-Nathan is a private practice therapist and Director of Trauma Services, Director of Training and Clinical Director at Sameen Associates, Inc. Prior to joining Waltham Behavioral Health, LLC, she was the Clinical Director of Lifecycle Counseling Center and the Director of the Cambridge Hospital Crisis Team. Suzanne Brennan-Nathan received a Master of Social Work from Smith College. Ms. Brennan Lambert has held teaching positions with Boston University, Simmons College, Smith College and Boston College. Ms. Lambert is a member of the National Association of Social Workers, American Group Psychotherapy Association, New England Group Psychotherapy Association, and the New England Society for the Treatment of Trauma.

Prior to joining Waltham Behavioral Health, LLC, he was a nurse practitioner in multiple departments at Massachusetts General Hospital and a nurse manager at Pine Street Inn. He was also a nurse practitioner at the Barbara Mcinnis House Respite, Boston Health Care for the Homeless. Christopher Shaw received a Post Master’sCertificate in Psychiatric Nursing   from the University of Massachusetts, Lowell and a Masters in Nursing  from the University of Massachusetts Boston. Mr. Shaw is an active member of the International Nurses Society of Addictions, and present board member and past president of the Association of Nurses in AIDS Care. In addition, he is the cofounder and Board Secretary of NPO Sibusiso.

Christine Aposhian received a Doctor of Education in Counseling Psychology from Boston University and a Master of Education in Counseling from Boston University.

Roselle served as staff social worker at Boston Medical Center for twelve years working on the oncology, spinal cord and inpatient psychiatric units as well as the outpatient psychiatric units. Additionally, she was part of a group practice serving adults, children, and families and has maintained a private practice since 2002. For the past several years Roselle has worked as a mental health clinician within the Massachusetts state and county prison system. Her work there has included treating male inmates and detainees struggling with mental illness, substance abuse, and trauma, as well as providing consultation to the prison’s medical and security staff. Roselle is a member of the National Association of Social Workers and has participated in the education, training, and supervision of social work interns.

Before joining Waltham Behavioral Health Ms. Korber gained wide-ranging expertise in various roles. Susan has worked as a Clinical Nurse Specialist at Sameem Associates in Newton, MA and at Nova Psychiatric and Neuro Behavioral Associates in the Greater Boston metropolitan area. Her resume also includes work in the Outpatient Department at Tufts New England Medical Center as well as a tenure on the Inpatient Psychosomatic Unit at Boston’s Children’s Hospital. Additionally, for the past sixteen years, Susan has worked at Italian Home for Children in acute residential, long-term residential and outpatient-care settings providing children, adults and families medication evaluation and treatment assessment. Susan received her Bachelor of Science in Nursing from Simmons College and her Master of Science in Psychiatric Nursing from Boston University. She is Board Certified through the American Nurses Credentialing Center.