Cortisol and eating disorders
I was excited to see that my recent survey about sleep/wake habits here on the blog supported my hypothesis: that those with restrictive patterns tend to rise earlier, and those with more binge/purge patterns rise later. Of course, in order to really look at the data, I'd need to compare the early bird and night owl percentages of each category with those of a non-ED sample.
Although many things affect circadian rhythm--most of which are under genetic control--one of the key hormones is cortisol. Released from the adrenal cortex, cortisol levels generally peak upon waking and reach a low point shortly after you go to sleep. What's more, cortisol is released during times of stress or anxiety, increasing both blood pressure and blood sugar.
A PubMed search of eating disorders and circadian rhythm produced mainly results on night eating syndrome. However, one study found a negative correlation between awakening cortisol response and "high anxiety, disinhibition and hunger scores, as well as poor body esteem and a high weight preoccupation" in women, but not men. That means that women with a low awakening cortisol response have high levels of anxiety, poor body esteem, etc. Of course, we don't know if this is cause or effect- just that it exists.
A study in men found a significant relationship between cortisol and perfectionism, which makes sense. Perfectionism is stressful (and don't I know that!), and higher stress means higher cortisol. As well, abnormalities in cortisol have been found in other psychiatric disorders, such as depression.
And indeed, women with anorexia were found not only to have higher cortisol levels but a significant proportion lacked a circadian cortisol rhythm. These abnormal cortisol levels are directly related to the starvation state- after weight restoration, cortisol levels return to normal. I'm not sure how the lack of cortisol rhythm is important. In general, starvation disturbs the sleep cycle, and refeeding is typically associated with improvements in sleep. The general school of thought is that the body is urging the starving person to go get food, and this may be true. But the high levels of cortisol brought out by the stress of malnutrition and starvation may also play a role.
High cortisol levels in people with AN have been positively associated with both osteoporosis and
hyperactivity.
Although one study found that overall daily cortisol rhythms in normal weight bulimic women were pretty much the same as in healthy women, another found evidence of greatly increased cortisol levels. It appears that, in bulimia, cortisol levels might be much higher than usual, although they still have a daily rhythm, unlike in anorexia. Even recovered bulimic patients continued to show a hyperreactivity to corticotropin-releasing hormone, which stimulates the release of cortisol, indicating an underlying neuroendocrine dysfunction.
Yet when cortisol levels were examined in relation to impulsivity, researchers found an inverse relationship between cortisol levels and impulsivity:
Patients with bulimic symptoms had significantly higher rates of cortisol suppression than controls and than restrictive anorectic patients. Percent cortisol suppression showed a strong and significant correlation with the patient's score on the Barratt Impulsiveness Scale. A hypersensitive cortisol response to dexamethasone, which might reflect hypothalamic-pituitary-adrenal axis dysfunctions might be specifically associated with impulsive subtypes of eating disorders.
Clearly, cortisol is just one player on a much larger field. Nor is it clear whether abnormalities in cortisol levels are cause or effect, and perhaps it's a little bit of either. Certainly the eating disorder exaggerates any underlying abnormalities. Whether the ED behaviors themselves cause the specific differences observed in cortisol levels in anorexia and bulimia, or whether these differences are part of the underlying risk factors for these illnesses also remains unclear.
Any questions?
13 comments:
This is really interesting. I've been reading up on cortisol and adrenal hormones; I have hypothyroidism which has apparently gone untreated for quite some time, which can in some people result in adrenal fatigue - low cortisol, abnormal cortisol rhythms, and so on.
My doctor says that not only can it cause or contribute to the anxiety and depression that people with chronic illnesses often have, but also be a cause of general irritability, inability to deal with social situations, finding noise stressful and irritating, being defensive about one's behaviour and taking things personally, being easily startled, disliking bright light, and similar symptoms. Stimulants such as caffeine can make it worse.
Low cortisol can also contribute to malnutrition, particularly low potassium and chronic hypoglycemia, and through intestinal upsets. And depending on individual responses, lack of appetite or food cravings.
Thinking about all this makes me want to go back to school and study human biology so I can understand the connections better.
Thank you - I'll be hitting PubMed as soon as I get back to work on Tuesday. My son has had irregular sleep cycles for a long time, getting by on 4 hours or less and dragging himself through the day with large amounts of caffeine. (How many times have I begged him to drink juice or milk instead?) We (his team and I) got him off caffeine over the summer but he still tries to function on little sleep, to the result that he cannot stay awake for classes or studying. You'd think such a smart kid would make the connection but recently has decided that raisins help him stay awake. I'll take it. Nibbling raisins is far better than swilling Diet Coke.
He has a full schedule of appointments over semester break soon. I'm going to call ahead to get his docs thinking about this.
There could be some evolutionary advantage to having a screwy sleep cycle if you're starving: what are you doing wasting time in bed when you could be searching for food? Cells/tissues/organs find all kinds of ways to scream for nutrition when we deprive them, using hormones, etc. That's entirely postulation, but it seems plausible, similar to the argument that some ED behaviors could be seen as adaptive in times of famine, such as hyperactivity despite calorie deficit.
Great post, I didn't know about the awakening cortisol response, fascinating!
Thanks for the cortisol education :) I'm absolutely sure this plays a role in my anorexia. I just hadn't read much about it until now. What's interesting is that my dr put me on birth control to help regulate my wacky periods and I was taking it at night, then waking at 2-3am, wide awake and alert. She said it was related to cortisol imbalance from the hormones. I really think anorexia messes with hormones in so many ways (and bcps don't help matters either).
This was very interesting to read. Since cortisol is a "stress" hormone, it definitely makes sense.
I also think a lot of anorectics have disturbed sleeping patterns due to sleep deprivation. I don't know if it was just me, but I would prevent myself from sleeping in order to "be more productive." Cortisol may have also been a factor in the fact that I was sleeping so little.
I think sleep deprivation in people with EDs is rampant. In fact, it was my pattern long before my ED really started. I stayed up until 2 am in high school.
Sad Mom,
I'm not saying don't have your son's cortisol levels checked, but I'm going to guess that they're high. And they will normalize when he starts eating better and normalizing his sleep habits. I'm not sure what kind of information this will give you, although an objective your-body-is-whacked may be useful. Or not. I was blithely unbothered by abnormal lab results. In fact, the AN actually encouraged me!
My late-night munchie of choice (when I would allow myself to munch) was pretzels. Along with Diet Coke and coffee. Sigh.
Cammy,
And I think you're very right. If there's a chance you could get food, your body doesn't want to waste it by sleeping. And I'm betting that cortisol is a part of that picture. I'm not sure what leptin and ghrelin and NPY do to circadian rhythm, but I know they are somewhat related to cortisol.
Carrie,
I have a post idea that would be somewhat off-topic from your normal posts, but it IS related to dealing with the ramifications of an eating disorder (as well as the types of activities that we sometimes encouraged to pursue in our recovery.) Like many girls who have had AN, I now have low bone density (osteoporosis-grade bone loss in two places, though it cannot be officially diagnosed without menopause, and osteopenia in another.) I am weight restored and am still grappling with doing what I can to prevent further bone loss and to allow my bones to regrow as my doctor says they can.
I obviously know that walking, running, and strength training (weight bearing exercises) are the best to help with this problem, while the low-impact (swimming, stationary bike, elliptical) doesn't do much to help out. So, I pound the pavement diligently on a walk a few times a week and begrudgingly lift weights (which I hate.)
But what about yoga? Almost everyone I have met who has been to treatment has been encouraged to try some type of yoga, but I've never really discovered conclusive info about whether this is classified as a weight-bearing exercise that will aid in osteoporosis prevention or control. Sure, it helps with feeling "at home" in your body and it has helped me greatly to extend some grace to my body and to connect my body with strength, but does it do anything for my bones?
I've done some light browsing on the topic, but I'd be interested in your thoughts after some research assimilation since I consider you a research guru in things related to EDs! I'd also be interested in your thoughts on the inclusion of physical activities like yoga in treatment.
Sarah
So interesting! I have LONG looked for more info about this, since it seemed ALL of us in treatment had a horrible time getting to sleep.
I think more studies should also be done on the effects eating disorders have on melatonin, as well, as that has a lot to do with your sleep cycle as well. It's hard to get accuracy without hardcore research.
I think some of it, at least for extremely medically unstable patients, could be the body fighting to keep from sleeping, because sleep is when the body repairs itself.
This is interesting. I'm anorexic (at the age of 49) and was once told that I was infertile because of exceptionally high cortisol level (in my 20's - I was anorexic then too). The doctor said it was so high that he wanted to present my case to a conference!
There must be a link.
I've never dieted. I've always been thin.
About a year ago, I was in the ICU with a close to 0 cortisol level. I had been in recovery from a ~10-year hx of AN for a year and had just started relapsing a month prior to the hospitalization.
Any info on LOW cortisol in AN?
(Sorry, I know this post is old!)
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