A two-study investigation into the link between rumination and night eating, and symptom improvement following a mindfulness-based intervention

Abstract

Night eating syndrome (NES) is characterized by a circadian delay in eating and nocturnal awakenings with ingestions. Its onset is related to stress and the syndrome is linked to depressed mood, anxiety, sleep problems, and obesity. Among patients with clinical depression, night eaters report greater rumination than non-night eaters. The objective of Part A of this study was to investigate whether a link between rumination and NES severity exists in a nonclinical sample of students after accounting for severity of depression symptoms. Several online self-report measures were completed by 713 students (mean age = 20.72 years, SD = 4.76). Night eaters (n = 47) reported higher levels of perceived stress, rumination, depression symptoms, trait and state anxiety, and poorer sleep quality than non-night eaters (n = 666). NES severity explained a small but significant portion of variance in rumination after accounting for depression symptoms. The objective in Part B was to examine the effectiveness of a novel mindfulness-based intervention (MBI) for the treatment of NES using a single blind parallel design. Night eaters (N = 17; mean age = 24.18 years, SD = 6.20) participated in a four-week MBI in which eight were randomly assigned to the MBI group and nine to the waitlist control group using a simple 1:1 allocation ratio. Following the intervention, the MBI group reported a significant decrease in NES severity, rumination, and perceived stress. However, over the same period of time, the waitlist group also reported decreases in these variables. Although no statistical significance was found when comparing both groups in the amount of change they experienced, an examination of effect sizes showed that the MBI increased night eaters’ mindfulness (large effect size; no change in waitlist), improved their sleep quality (medium effect size; worse sleep quality in waitlist), and decreased depression symptom severity (small effect size; larger decrease in MBI group), which is suggestive of clinically significant improvement. Overall, the MBI was successful in increasing mindfulness but did not affect rumination. As such, rumination was not found to explain any benefits following the MBI. It appears that it is largely the presence of depression symptoms that explains the relationship between NES severity and rumination, suggesting that night eaters with co-morbid depression may be at increased risk of psychopathology. Mindfulness, however, may be a promising intervention for improving depression symptoms among night eaters.