Background. Sleep-related eating disorder is a little-described syndrome combining features of sleep disorders and eating disorders. The behaviour consists of partial arousals from sleep followed by rapid ingestion of food, commonly with at least partial amnesia for the episode the following day. The aim of this study was to provide an estimate of the prevalence of sleep-related eating disorder.

Methods. The Inventory of Nocturnal Eating, a self-report questionnaire addressing nocturnal eating and sleep disturbance, was administered to out-patients (N=126) and in-patients (N=24) with eating disorders, obese subjects (N=126) in a trial of an anorexic agent, depressed subjects (N=207) in an antidepressant trial, and an unselected group (N=217) of college students. Sleep-related eating disorder was operationally defined as nocturnal eating with a self-reported reduced level of awareness, occurring at least once per week.

Results. Almost 5·0% (33/700) of the sample described symptoms consistent with sleep-related eating disorder. The in-patient eating disorders group had nearly twice the prevalence (16·7%) of the out-patient eating disorder sample (8·7%), which had nearly twice the prevalence of the next highest group, the student sample (4·6%). Subjects with sleep-related eating disorder endorsed more symptoms consistent with sleep disorders and had higher levels of depression and dissociation than those without nocturnal eating.

Conclusions. Sleep-related eating disorder is more common than is generally recognized, especially in those with a daytime eating disorder. Sleep disorder symptoms are often associated with sleep-related eating disorder, as are depression and dissociation. Evaluation of individuals with eating disorders should include assessment for sleep-related eating.