According to percentage distribution of students ages 3–21 served under the Individuals with Disabilities Education Act (IDEA), by disability type: School year 2017–18, 5% of all disabled students are with emotional disturbance
Mental, behavioral, and developmental disorders begin in early childhood; 1 in 6 U.S. children aged 2–8 years (17.4%) had a diagnosed mental, behavioral, or developmental disorder (Bitsko, R. H. et al, 2016)