A narrative review on the similarities and dissimilarities between [ME/CFS] and sickness behavior, 2013, Morris et al

A narrative review on the similarities and dissimilarities between myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS) and sickness behavior

Gerwyn Morris, George Anderson, Piotr Galecki, Michael Berk, Michael Maes

Abstract
It is of importance whether myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS) is a variant of sickness behavior. The latter is induced by acute infections/injury being principally mediated through proinflammatory cytokines. Sickness is a beneficial behavioral response that serves to enhance recovery, conserves energy and plays a role in the resolution of inflammation. There are behavioral/symptomatic similarities (for example, fatigue, malaise, hyperalgesia) and dissimilarities (gastrointestinal symptoms, anorexia and weight loss) between sickness and ME/CFS. While sickness is an adaptive response induced by proinflammatory cytokines, ME/CFS is a chronic, disabling disorder, where the pathophysiology is related to activation of immunoinflammatory and oxidative pathways and autoimmune responses. While sickness behavior is a state of energy conservation, which plays a role in combating pathogens, ME/CFS is a chronic disease underpinned by a state of energy depletion. While sickness is an acute response to infection/injury, the trigger factors in ME/CFS are less well defined and encompass acute and chronic infections, as well as inflammatory or autoimmune diseases. It is concluded that sickness behavior and ME/CFS are two different conditions.

Link | PDF (BMC Medicine) [Open Access]

 

Is a gag reflex sickness behavior?

This was a decade ago.

I remember when I was a Gerwyn fan (if I've the right Gerwyn).

I still miss those "concepts."

 

They understand the importance of PEM in definining ME/CFS, and spend a lot of the paper talking about it, which is nice:

The symptom simarities they list:

I'd love to see evidence of PEM in sickness behavior, but I don't see them cite anything. Though I may have missed it somewhere else in the paper.

One of the main reasons they give for the two conditions being different is that sickness behavior includes anorexia (decreased hunger) and pyrexia (fever), while ME/CFS, as a rule, doesn't.

This isn't satisfying to me. For a relatively short duration of acute infection, decreased food intake is totally fine and survivable for a person. Of course that couldn't continue forever or the person would starve, so if sickness behavior persisted for months, the body would have to override that feature of the response. I assume a similar reasoning would explain why fever doesn't persist for months. The cost to the body could be greater than the reward if it persists.

Not to mention, I don't think fever or anorexia is even always required in sickness behavior. At least for me, I don't remember the last time I got a fever from an infection. (Although I don't normally measure my temperature, but it doesn't feel like it.) And I don't stop being hungry when sick. (Sidenote: Is this lack of fever during acute sickness common in ME/CFS?)

Another reason they give seems to just be semantics, basically saying sickness behavior, by definition, describes a brief period, so it can not be involved in ME/CFS. I'm interested in whether the physiology is similar.

Then there are some reasons given for physiological dissimilarities, such as the specifics of inflammation markers. Most of it is over my head, so I can't comment on it.

Wikipedia includes other objectives that I didn't see mentioned in this paper, though I might have missed them, including signalling to others that one is sick, and staying away to not infect them.

I haven't looked at these citations, but some of this looks interesting:

I personally think that it's most likely ME/CFS symptoms are caused by a live, replicating pathogen, and something similar to "sickness behavior" is causing the symptoms. The reasons being the profound symptom similarities between the two, which the paper listed above, as well as the obvious connection to infection that ME/CFS has. But most of all, I think a replicating pathogen is the most obvious explanation for PEM, as it explains the delayed onset (time for the pathogen to replicate), and I think that should be one of the first PEM mechanism theories to try to falsify. If the paper's claim is true that a PEM like symptom is seen in normal sickness behavior, I think that would strengthen the case even more.

One counterargument I can think of is the question, why don't we ever see the pathogen in ME/CFS replicate to high enough levels that it kills the person? One possible explanation could be that the sickness response is very overexaggerated in relation to the pathogen levels, and even in very severe ME/CFS, it is still nowhere near life threatening levels. Or maybe the body can keep it localized to a place where it can't actually do significant damage.

The reason I went looking for "sickness behavior" papers is that I thought I had heard or read that the body can basically "turn off" sickness behavior temporarily during an emergency, where the body feels pretty much normal for a time, so that the problem can be handled. I haven't found anything about that, so maybe I'm misremembering. But I was wondering if there might be some marker of that, like an adrenaline or cortisol pathway, which might also be able to be tested for in the brief "adrenaline"-like periods of ME/CFS where a person feels much more energetic if there's an important task or a lot of excitement.

 

I have no idea if it is common or not. I had no fever at all during glandular fever (which was my trigger), even though I had a whole range of other symptoms, including some less common ones, like the swollen eyelids that even obscured my vision one morning. My lymph nodes were so swollen that my neck was wider than my head (not an exaggeration), I had really bad lower back pain (due to the lymph nodes there I guess), etc etc. I was feeling pretty awful and I wouldn't call it super mild but I still had no fever at all.

I did have debilitatingly high fever during my two bouts of influenza before my ME/CFS and some less debilitating fever during my covid infection after my ME/CFS onset.

 

I've never had a fever in 33 years of ME and I've experienced a lot of viral infections. My ME onset was a sudden viral onset, sore throat/ear vertigo. high antithyroid antibodies, strep throat but never a fever.

I never had a fever when I contracted COVID 2 years ago and I was quite sick for several weeks. I started feeling better one month later only to worsen again after I went for a 45 minute walk. Only my legs were affected during that time around.