The LAMS study investigated how symptoms of mental disorders develop from childhood to early adulthood within a clinic-based cohort of children with elevated symptoms of mania (ESM+) and without ESM (ESM−). Between 2005 and 2008, children aged 6- to 12 years were recruited from 10 out-patient mental health clinics in Ohio and Pennsylvania, United States of America, and screened for the presence or absence of ESM. At baseline, the longitudinal cohort included 621 children who screened ESM+, along with a comparison group of 86 demographically-matched children without ESM. The children, along with their caregiver, were followed up approximately every six months for up to eight years.