Validation of the Night Eating Diagnostic Questionnaire (NEDQ) and its relationship with depression, sleep quality, "food addiction", and body mass index.

Night eating syndrome (NES) is commonly assessed using the Night Eating Questionnaire (NEQ), a validated scale of symptom severity, which does not assess all diagnostic criteria. The Night Eating Diagnostic Questionnaire (NEDQ) assesses all diagnostic criteria, but has not been fully validated. The study purpose was to establish convergent validity for the NEDQ with the NEQ. It was also expected that higher NEDQ scores would be associated with elevated depression, poorer sleep quality, "food addiction," and BMI as in other studies of NES. Students (n = 254) and community members (n = 468) were administered the NEQ, NEDQ, Pittsburgh Sleep Quality Index, Zung Self-report Depression Scale (SDS), and the Yale Food Addiction Scale (YFAS). Convergent validity between the NEDQ and the NEQ was demonstrated; the scores were significantly positively correlated. There was good agreement between the NEDQ and the NEQ in diagnosis of NES; 56% of those diagnosed by the NEDQ met the threshold score on the NEQ, while the other 44% did not. Only 5 participants out of 33 who met the NEQ threshold score for NES did not meet the NEDQ diagnostic criteria. MANOVA revealed that higher NEDQ was associated with higher SDS and YFAS scores and poorer sleep quality. Full-syndrome NES by the NEDQ was associated with higher BMI in the community group unlike the student group. Scores on all the other questionnaires were higher in the community group. The discrepancies between NEDQ and NEQ diagnosis may be due to differences in construction of the questionnaires and specifically due to the NEDQ being designed for diagnosis. The NEQ provides a convenient global score for NES severity, whereas the NEDQ, which shows convergent validity with the NEQ, provides clinically useful diagnostic categories.