disorder, provides a distinct ca tegory for such presentations. 
Prevalence
Disruptive mood dysregulatio n disorder is common among children presenting to pedi-
atric mental health clinics. Prevalence estima tes of the disorder in the community are un-
clear. Based on rates of chronic and severe pe rsistent irritability, which is the core feature
of the disorder, the overall 6-month to 1-year period-prevale nce of disruptive mood dys-
regulation disorder among children and adolescents probably falls in the 2%–5% range.
However, rates are expected to be higher in males and school-age children than in females
and adolescents. 
Development and Course
The onset of disruptive mood dysregulation diso rder must be before age 10 years, and the
diagnosis should not be applied to children with a developmental age of less than 6 years.
It is unknown whether the condition presents only in this age-delimited fashion. Because
the symptoms of disruptive mood dysregulat ion disorder are likely to change as children
mature, use of the diagnosis shou ld be restricted to age grou ps similar to those in which
validity has been established (7–18 years). A pproximately half of children with severe,
chronic irritability will have a presentation that  continues to meet crit eria for the condition
1 year later. Rates of conversion from seve re, nonepisodic irritability to bipolar disorder
are very low. Instead, children with chronic irritability are at risk to develop unipolar de-
pressive and/or anxiety disorders in adulthood. 
Age-related variations also differentiate cl assic bipolar disorder  and disruptive mood
dysregulation disorder. Rates of bipolar disorder generally are very low prior to adoles-