Evaluation of diagnostic criteria for night eating syndrome using item response theory analysis.

Uniform diagnostic criteria for the night eating syndrome (NES), a disorder characterized by a delay in the circadian pattern of eating, have not been established. Proposed criteria for NES were evaluated using item response theory (IRT) analysis. Six studies yielded 1,481 Night Eating Questionnaires which were coded to reflect the presence/absence of five night eating symptoms. Symptoms were evaluated based on the clinical usefulness of their diagnostic information and on the assumptions of IRT analysis (unidimensionality, monotonicity, local item independence, correct model specification), using a two parameter logistic (2PL) IRT model. Reports of (1) nocturnal eating and/or evening hyperphagia, (2) initial insomnia, and (3) night awakenings showed high precision in discriminating those with night eating problems, while morning anorexia and delayed morning meal provided little additional information. IRT is a useful tool for evaluating the diagnostic criteria of psychiatric disorders and can be used to evaluate potential diagnostic criteria of NES empirically. Behavioral factors were identified as useful discriminators of NES. Future work should also examine psychological factors in conjunction with those identified here.