Circadian rhythm, a 24-hour cyclical process of sleep and waking hours, is associated with many aspects of human health and behavior. Chronotype, the preference for morning or evening, has may be a critical player linked to psychological, neurological, gastrointestinal, and respiratory disorders. Morning chronotypes prefer waking and sleeping early, whereas evening chronotypes prefer waking and sleeping late. Existing research has uncovered the two-way association between circadian rhythms and psychiatric disorders; a study published in the Journal of American Medical Association sought to explore the relationship between circadian rhythms and anorexia nervosa.
Anorexia nervosa, a severe eating disorder characterized by food intake restriction, weight loss, and an intense fear of gaining weight, has a high mortality rate among psychiatric diseases. Previous evidence hinted at a connection between anorexia nervosa and the circadian clock, manifesting in features like morning anorexia and evening hyperphagia.
The study used genetic association techniques, including Mendelian randomization (MR) and polygenic risk score (PRS), to investigate the relationship between anorexia nervosa, circadian and sleep traits. The analysis uncovered a compelling connection between anorexia nervosa and morning chronotype.
Sensitivity analyses attest to the robustness of these bidirectional associations. The findings disrupt conventional thought processes in the field. This study portrays anorexia nervosa as a morning eating disorder, contrary to the prevailing trend among other evening-based psychiatric diseases.
Morning, seemingly an overlooked risk factor for anorexia nervosa, could shape preventive strategies. Interventions promoting later sleep schedules may mitigate the risk conferred by a morning chronotype. Moreover, the study hints at the potential efficacy of bright light therapy in the evening, challenging the status quo of morning bright light therapy in anorexia nervosa treatment.
This study challenges the current school of thought on anorexia nervosa and provides a new perspective on the complexity of the relationship between psychiatric disorders and circadian rhythms.
Sources: Journal of American Medical Association, The National Library of Medicine