Hassan Dashti, PhD, RD: How Findings of Anorexia Nervosa Linked to Morning Chronotype Affects Treatment


In an interview, Hassan Dashti, PhD, RD, discusses the main takeaway of a study on anorexia nervosa being associated with the morning chronotype.

A new study found anorexia nervosa is associated with the morning chronotype, unlike other evening-based disorders like depression.1,2

The study, led by Hannah Wilcox, BS, from Massachusetts General Hospital, evaluated the association between anorexia nervosa and circadian and sleep traits, such as daytime napping, daytime sleepiness, sleep duration, and insomnia, through mendelian randomization. The investigators found an association between insomnia and the risk of anorexia nervosa but no associations association with the other sleep traits.

In an interview with HCPLive, Hassan Dashti, PhD, RD, from Massachusetts General Hospital, discussed how disturbed sleep serves as a risk factor for eating disorders and how the research lays the groundwork for thinking of new anorexia nervosa treatment, such as potentially implementing treatments related to circadian rhythm and sleep.

Can you summarize the study’s findings?

Dashti: What we’re interested in looking at is the relationship between anorexia nervosa and sleep treats, including chronotype, which reflects sleep timing, using a new approach called min Delia and randomization. The strength of this approach is that unlike observational data, which relies on self-report…and is heavily influenced by other comorbidities, or other environmental factors that might obscure the relationship between a disease and an outcome, this approach is genetics.

What we found…is that people with anorexia nervosa tend to be early risers or have an early or morning chronotype compared to people without anorexia nervosa. What this tells us is that their circadian rhythms are advanced, they are early, they have earlier circadian rhythms compared to people without the disorder. This is unique because more psychiatric disorders tend to have delayed circadian rhythms more evening-based like depression, anxiety, and schizophrenia.

We also found that being a morning person also predisposes might be a risk factor for developing anorexia nervosa. So, it was a two-way relationship.

What would you highlight as the biggest takeaway?

Dashti: Biggest takeaway is to really start looking at sleep as potentially a risk factor or disturbed sleep as a risk factor for eating disorders.

[The] bigger takeaway is trying to think of how could… circadian rhythms and sleep related treatments or strategies could be used in the prevention and treatment of eating disorders, specifically here, anorexia nervosa.

How will bright light therapy in the evening versus bright light therapy in the morning impact anorexia nervosa treatment?

Dashti: We know that bright light therapy influences the circadian clock because light or exposure to light advances or delays the clock depending on when we are exposed to that bright light. So, for people with depression, for example, bright light therapies typically in the morning could help reset their clock and advance their rhythms, but for somebody with advanced circadian rhythms perhaps what we need to do is use bright light therapy in the evening in order to prolong their clock.

What we hypothesize will happen is that bright light therapy in the evening will advance their circadian rhythms, help people extend their day, go to bed later, wake up later. And perhaps if it's true that and an advanced circadian rhythm increases the risk for anorexia nervosa, then perhaps that would be one way to attenuate or potentially treat someone treat symptoms of the disease and potentially prevent the disease as well.

Is there any other treatment like bright light therapy that would be impacted by the new knowledge that anorexia nervosa is a morning chronotype?

Dashti: Doing this only makes sense, I believe, if a patient is not suffering from other psychiatric disorders. Now, one thing to consider is a person as a whole, and all their psychiatric disorders that they might be living with. Typically, people with eating disorders also suffer from anxiety and depression, and for those diseases, bright light therapy in the morning might be the best approach.

We think therapies need to be tailored, they need to consider a person as a whole. What our findings suggest is that perhaps where a person with anorexia, who luckily is not experiencing other psychiatric disorders, then focusing on this morning, this relationship might be more relevant. However, if they’re also living with other psychiatric disorders, like depression and anxiety, it might be the case where we need to prioritize pretreatments for those other diseases first, might be the best approach.

Can you discuss the association between insomnia and the increased risk of anorexia nervosa?

Dashti: What others have shown and what we have shown here is that people living or people who might have disturbance in sleep, either difficulty falling asleep, difficulty maintaining sleep or difficulty waking up, might increase their chances of developing an eating disorder in our case of anorexia nervosa. Now, why is that happening? We don't really know. Perhaps waking up in the middle of the night causes people to think about body image or developing negative association with food. Those could be potential reasons.

What were some challenges faced in the study?

Dashti: The genes, the anorexia, genes that we are using based off of a previous study were identified in a primarily European cohort or European population. Our findings could be, for the most part generalized to people of European descent. Whether our findings are relevant to other racial and ethnic groups still unknown, and it’s our responsibility to investigate this further.

Another limitation is that our approach again tells us more about causal associations but doesn't necessarily tell us why.

The third limitation is that it doesn’t give us precise effects. A lot of questions I get is what time should we wake up to attenuate our risk for anorexia nervosa, we can say for sure what the best wake up time is, or the best bedtime is these are things that we need to further explore and additional studies.

Is there anything else you would like to say before we wrap up here?

Dashti: I just want to reiterate the uniqueness of our findings. Most psychiatric disorders are evening-based diseases. And now for the first time, we’re seeing a disease that is somewhat of a morning-based disease.

Now there’s a huge shift, or there's a huge movement, promoting time restricted eating or intermittent fasting. People generally do intermittent fasting by fasting in the morning not eating anything in the morning, and this might actually be a dangerous thing to do because it might now…exacerbate other diseases including promoting eating disorders.

We need to do more work to better understand what precise sleep and circadian rhythm strategies might be effective in the treatment and prevention of anorexia nervosa.

Among our psychiatric disorders, eating anorexia nervosa ranks as the second most lethal psychiatric disorder. It might not be the most common, but it is the most deadly, and there are very, very few treatment options available for people living with the disease. We’re hoping that this that these findings open up new options for treatments.


  1. Derman, C. Anorexia Nervosa Associated with Being an Early Riser. HCPLive. January 5, 2024. https://www.hcplive.com/view/anorexia-nervosa-associated-with-being-an-early-riser. Accessed January 5, 2024
  2. Wilcox H, Paz V, Saxena R, Winkelman JW, Garfield V, Dashti HS. The Role of Circadian Rhythms and Sleep in Anorexia Nervosa. JAMA Netw Open. 2024;7(1):e2350358. Published 2024 Jan 2. doi:10.1001/jamanetworkopen.2023.50358
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