Does being a morning person increases one's chances of developing an eating disorder? Researchers have found a bidirectional association between anorexia nervosa and morning chronotype - the natural inclination of the body to wake up and sleep early.

Anorexia nervosa is an eating disorder that causes an intense fear of gaining weight. People with the condition have a distorted body image that makes them severely restrict the amount of food they eat. To prevent weight gain, they may resort to vomiting after eating, exercise excessively, or misuse laxatives, diet aids, diuretics, or enemas.

Earlier studies have shown a possible link between eating disorders and the circadian clock that controls several bodily functions such as sleep. Many disorders such as depression, binge eating disorder and schizophrenia were associated with the evening chronotype.

In the latest study, published in Jama Network Open, researchers found that anorexia nervosa is associated with being an early riser. The team also established an interesting link between anorexia nervosa and insomnia risk.

Researchers conducted a genetic association study that included 16 992 cases and 55 525 controls. They noticed a two-way association between genes associated with anorexia nervosa and genes associated with morning chronotype. This means that being an early riser could increase the risk of having anorexia nervosa, and vice versa.

"Genetic liability for anorexia nervosa was associated with a more morning chronotype and conversely, genetic liability for morning chronotype was associated with increased risk of anorexia nervosa," the researchers wrote.

"Our findings implicate anorexia nervosa as a morning disorder in contrast to most other evening-based psychiatric diseases and support the association between anorexia nervosa and insomnia as seen in earlier studies," senior author Hassan S Dashti said in a news release.

Anorexia nervosa has the second-highest mortality rate among psychiatric disorders. Treatment options for anorexia nervosa are limited, and the relapse rates are as high as 52%. Furthermore, the cause of the eating disorder remains unclear.

"The clinical implications of our new findings are currently unclear; however, our results could direct future investigations into circadian-based therapies for anorexia nervosa prevention and treatment," said Hannah Wilcox, lead author of the study.