There is a need for newer, more clinically useful classifications for insomnia. Identification of specific subtypes of insomnia helps anchor research, allows for prediction of prognosis/course of the condition, and may allow for individualization of treatment. Existing classifications differ, and many terms remain inadequately defined, which leads to diagnostic confusion. Historically, insomnia has been classified according to symptom type, symptom duration, and underlying cause, but these classifications have not been based on evidence of their utility, and newer research suggests the need for change.