A serious emotional disturbance is defined by the Individuals with Disabilities Education Act (IDEA), Public Law 101-476, as follows:
A condition exhibiting one or more of the following characteristics, displayed over a long period of time and to a marked degree that adversely affects a child's educational performance:
An inability to learn that cannot be explained by intellectual, sensory, or health factors
An inability to build or maintain satisfactory interpersonal relationships with peers or teachers
Inappropriate types of behavior or feelings under normal circumstances
A general pervasive mood of unhappiness or depression
A tendency to develop physical symptoms or fears associated with personal or school problems.
This term includes schizophrenia, but does not include students who are socially maladjusted, unless they have a serious emotional disturbance. P.L. 105-17, the IDEA Amendments of 1997, changed "serious emotional disturbance" to "emotional disturbance." The change has no substantive or legal significance. It is intended strictly to eliminate any negative connotation of the term "serious."
Mental health issues are much harder to quantify than physical problems. We have more statistics that quantify the risk factors for mental health issues than we do statistics on how many children have specific mental health issues.
One significant study is the KidsCount data collected by the Annie E. Casey Foundation.
KIDS COUNT is a national and state-by-state project of the Casey Foundation to track the status of children in the United States. At the national level, the principal activity of the initiative is the publication of the annual KIDS COUNT Data Book, which uses the best available data to measure the educational, social, economic, and physical well-being of children state by state. The Foundation also funds a national network of state-level KIDS COUNT projects that provide a more detailed, county-by-county picture of the condition of children. The first national KIDS COUNT Data Book was published in 1990.
"The state indicators in the rankings under KidsCount look at the different factors that effect the overall well being of children in any state, like the number of children living in poverty, the death rate, the number of children who are physically or emotionally abused or are sexually abused, the number of drop outs, the number of expulsions from school, the number of children with food stamps. Because you can’t separate out mental health from physical health from those factors, then you have to assume that if a child is in a more challenging environment, if the poverty is higher, if they have more health problems in their family, that they have more physical issues and families have more problems...the number of mental health problems will be increased."