Bruxism into three groups, namely central or pathophysiological factors, psychosocial factors and peripheral factors. The World Health Organization's International Classification of Diseases 10th revision does not have an entry called bruxism, instead listing "tooth grinding" under somatoform disorders. To describe bruxism as a purely somatoform disorder does not reflect the mainstream, modern view of this condition (see causes). The ICSD-R described three different severities of sleep bruxism, defining mild as occurring less than nightly, with no damage to teeth or psychosocial impairment; moderate as occurring nightly, with mild impairment of psychosocial functioning; and severe as occurring nightly, and with damage to
Bruxism over 50% of normal infants. Often sleep bruxism develops during adolescence, and the prevalence in 18- to 29-year-olds is about 13%. The overall prevalence in adults is reported to be 8%, and people over the age of 60 are less likely to be affected, with the prevalence dropping to about 3% in this group. A 2013 systematic review of the epidemiologic reports of bruxism concluded a prevalence of about 22.1–31% for awake bruxism, 9.7–15.9% for sleep bruxism, and an overall prevalence of about 8–31.4% of bruxism generally. The review also concluded that overall, bruxism affects males and females equally, and