Mattson started working with Sea Mar in March 2019 as a behavioral health therapist with the Behavioral Health Clinic in Bellevue. Mattson is licensed as both a Mental Health Counselor Associate (LMHCA) and a Chemical Dependency Professional (CDP).

Mattson served as a chemical dependency counselor to some of Seattle's most vulnerable individuals while at Downtown Emergency Service Center (DESC). From there he wanted to expand his abilities to help others and returned to school to earn his Master's in Psychology from Saybrook University. Mattson recognizes that addiction issues are often symptomatic of other mental health issues and is grateful that he is able to treat both conditions.

Mattson enjoys spending time with his family and friends and playing guitar in his off hours.