Our Experts

A passion for helping others coupled with an intense curiosity for the world led Dr. Fellers down the path of medicine. As an addiction psychiatrist, he works with patients, families, and our health care system to promote high quality evidence-based screening, assessment, and treatment for substance use disorders and co-occurring mental disorders. Addiction and mental health disorders involve both biology and psychology, and his expertise enables him to disentangle this complexity. Dr. Fellers brings a holistic approach to medicine in order to find comfortable and effective solutions for everyone.

Naomi holds a master's degree in clinical mental health counseling and has years of experience in the behavioral health field. Prior to joining Cortex Behavioral Health, she worked in various roles in the Greater Portland community. This included providing crisis intervention support throughout Cumberland County, coordinating residential care for dual-diagnosed adults with a chronic illness, and facilitating addiction recovery for pregnant and postpartum mothers. Naomi takes a person-centered and trauma-informed approach to empower clients to explore and navigate their emotions while fostering a safe and non-judgmental space for healing. She is most interested in helping individuals work through major life transitions, encouraging them to lean into their values and strengths. Naomi integrates elements of cognitive-behavioral therapy, interpersonal therapy, dialectical behavioral therapy, motivational interviewing, and mindfulness practices into her work. When she is not counseling, she enjoys training Brazilian Jiu-Jitsu, being outdoors, traveling, and spending time with her nieces and nephews.

Dr. Johnnidis completed her psychiatry residency in Texas and recently relocated to Maine to complete her fellowship training in Child and Adolescent Psychiatry. At Cortex Behavioral Health, she treats patients of all ages, with added expertise in working with emerging adults. She provides comprehensive, evidence-based care for a broad range of psychiatric disorders, incorporating both medication management and psychotherapy to tailor each treatment plan to meet the unique needs of her patients. During her free time, she enjoys spending time with her fiancé and researching the latest stats for her fantasy football teams.

Born and raised in Maine, Colleen received her BSW and MSW from University of Maine.  Colleen has worked in substance use and co-occurring programs in Maine, primarily with young adults and in both extended care and short-term residential programs.​ Colleen began her career as a clinical therapist at a treatment center focused on co-occurring substance use and eating disorders. There she found her passion for providing comprehensive and holistic treatment to those impacted by substance use and co-occurring mental health disorders. Colleen engages with clients using cognitive behavioral therapy, acceptance and commitment therapy, dialectical behavior therapy, and solution focused therapy.  Outside of work, Colleen enjoys spending time with her friends, spinning at the local spin studio, walking her poodle, and listening to audiobooks.