Sickness behaviour – useful concept or psycho-humbug?

I suppose to split hairs, the so-called sickness behaviors such as fatigue, depression, etc are not directly behaviors as such; they are actually states of mind, but states of mind which then give rise to certain behaviors, or which modify behaviors.

So for example, obviously when you feel heavy fatigue, you don't tend to go out for a night on the town, but will more likely curl up on the sofa in front of the TV, or go to bed. In that sense, the fatigue state of mind controls outward behavior. The fatigue state sets the agenda.

The depressed state of mind will also modify behavior, and set a different behavioral agenda compared to the "full of beans" state of mind.


But as mentioned, we don't really need to get bogged down with psychology. The sickness behavior theory of ME/CFS is simply one that equates the symptoms experienced during an infectious episode like the flu with the symptoms of ME/CFS.

 

Does a patient not both experience the symptoms and observe its own behavior?

With animals I observed the symptoms and the behavior.

 

Not at all. The behaviour is what you do when a certain set of symptoms and a particular type of immune response is present.

 

Agreed that fatigue and depression aren't behaviours. The behaviour is taking yourself away from company, not taking care of your appearance, not eating, sleeping more than usual etc.

 

Fair enough, but who cares? What is driving the behavior is symptoms. It is a dangerous slope.

Yes, but what is behind the behavior? Again, we get one logical step behind with this approach, and it plays into the hands of people we do not agree with - at least potentially.

 

Yes! I'm always suspect of evolutionary accounts of everything, because they tend to cherry pick the phenomena that fit and ignore the others.

After reading @Mij's article, I'm favouring the idea that there is no wider social or adaptive purpose for sickness behaviour. Its just that the stuff you produce to fight infections gets in the way of normal body functioning. So you feel tired and lie down.

I'll post a summary of @Mij's article when I've finished it.

 

Interesting you should say that. Yes, the article reads very much like a fusing together of two literatures with out much real thought as to their real relation.

 

I agree, @Hip. I suppose that is the question of interest here. Does it mean anything to talk about "sickness behaviour"? Would it be better to talk about how inflammation can intefere with energy production and cause fatigue? I think this is better and less open to multiple interpretations.

Yes, Psychology starts to rear its ugly head further down the line.

1. It all starts innocently - with the suggestion that some behaviours we engage in when fighting an infection may be adaptive.

2. Then comes the idea that if these behaviours are so adaptive, then maybe they're "centrally coordinated' (mediated by the brain/CNS)

3. Then comes the idea that an abnormality within the brain/CNS may cause sickness behaviors in the absence of any infection

4. Then comes the idea that we can help intervene to stop these inappropriate sickness behaviours by "resetting" the person's brain in some way

5. Then you've got..... GET... psychotherapy....

 

Just reporting back on @Mij's article. The Maes one.

I'm not interested in what they have to say about ME right now. I'm interested in what they say about bodily responses to acute infection - whether there's evidence for a coordinated "sickness behaviour" response.

The review of what happens during actue infection is quite helpful. In contrast to the sickness behaviour idea, most of the studies they reference show that the various "behaviours" that accompany infection are NOT mediated by the brain. The mechanisms are mostly peripheral (e.g., cytokines interfere with mitochondrial activity, which leads to fatigue). Some changes involve the CNS - for example the systematic increasing in body temp seen in fever involves the hypothalamus. And the changes in heart rate and blood pressure involve the CNS signalling to the autonomic nervous system. Neither fever nor cardiovascular changes are "behaviours" strictly speaking, but I suppose they may contribute to the general shitty exhausted feeling that inclines you to want to rest.

So much for the centrally coordinated adaptive behavioural modification system. Not much support there.

The paper also reviews the ways in which the CNS might be involved in the whole bodily response to infection. A surprise to me was that the role of the CNS is largely in switching off the inflammation, not heightening it. They explain that peripheral inflammation can activate microglia and astrocytes in the brain via various routes (some cytokines, like TNFa, can cross the blood brain barrier efficiently; others operate more indirectly via the peripheral nervous system). In respnse, the brain up-regulates the production of glucocorticoids, which has an anti-inflammatory effect, and also initiates the release of catecholamines and acetylcholine, which also inhibit the production of proinflammatory cytokines (e.g. IL1, IL6 and TNFa), and also of T helper cells.

My conclusion:

• Low-level brain structures coordinate some body-wide responses to infection (fever, heart rate changes). But most of the changes leading to "sickness behaviour" occur outside the central nervous system. They are things like cytokines interfering with mitochondrial function.

• Sickness behaviour is not a useful concept. Its adds little, and is open to misinterpretation and abuse. A much clearer way to talk about behaviour changes that occur during an acute infection is simply to call them "behaviour changes that occur during an acute infection".

• As for its relation to MECFS, I don't think that matters, if the concept itself is stupid.

 

But that just isn't catchy and there's nothing we humans like more than a pithy phrase!

Many words and phrases are open to abuse, misinterpretation and sleight of hand re-interpretation, such as 'recovery' and 'functional'.

The problem is the abusers, not the abused.

 

My point was - this isn't really a thing. People thought it was a thing, but it turns out it really isn't a thing. So it don't need no name.

Edit: Sometimes giving things a name is the start of a whole big new problem. The thing takes on a life of its own. I'm thinking about depression here. Statements like "depression is often comorbid with ME" make the depression sound like a thing. If you substituted what you mean by depression, the statement would sound very different ("people with ME often have problems sleeping and feel sad").

 

It's all a bit above my head. I'll need to go away and think about it. I may be some time.

Ohhhhhh, yes!

Edited to add (before I go): the original 'depression' clearly is a thing, though, and was appropriate when it was first coined even though the mechanism was/is not understood. Since then, a lot of different things have all been muddled together to create a confused mess so that the word has lost all sensible meaning.

You can't not assign labels to 'things' or we'd stop being able to communicate altogether. Do we all mean the same thing by 'sad' or is that a proxy for other things.

I may once again have missed the point but I'm off now.

 

I agree.

 

Sorry, @Scarecow, I was having a silly moment. Must be watching too much John Oliver.

What I meant to say about sickness behaviour is this:



Meaning the concept doesn't have any integrity and is more likely to confuse and obfuscate than to enlighten.

 

That's exactly how I took it.

Too right!

 

I agree, it is an unhelpful concept. It carriesteleological or 'functional' baggage and is really only relevant to mice and dogs, where behaviour is what the vet has to go on.

The 'adaptive' argument is trendy but groundless. Many illnesses, including infections have symptoms that might arise through pathways that are useful in other situations (like vomiting following ingestion of toxic substances). That does not mean they are useful when hijacked by other illnesses. It would probably be just as advantageous to feel perfect bliss and retire to bed to enjoy it with flu as to feel rotten.

And every illness is different, which is why concepts like sickness behaviour just lead to imprecise science.

Illness behaviour is something quite different, as mentioned. It means fabricated symptomatology.

 

Does part of the problem in discussion of this subject come down to ambiguity over what it is that is supposedly doing the "behaving"?

One can see some sort of sense, although in an imprecise way in need of further development, in an idea that a mechanistic body, devoid of free will or personality might be thought of as displaying "sickness behaviour". When it is sick that is what it does. These are the physiological changes which occur.

The problem is that humans have difficulty seeing themselves in these terms and "behaviour" tends to be attributed, to greater or lesser extent, to the "ghost in the machine".

One suspects that there are a whole lot of category errors that need to be removed.

Perhaps if some word less ambiguous than behaviour were used there would be less objection, but it is hard to see what is added, other than a word, by considering sickness behaviour rather than sickness. The day I hear someone say "I'm suffering from sickness behaviour" I might change my mind.

 

Illness behaviour / sickness behaviour - I certainly never realised that the two terms were intended to be different! Does anyone really differentiate?

 

I thought that illness behaviour was a sociological term.

 

I think they are used by two quite different communities, neither of which is aware of the existence of the other term. They are intended to have quite different meanings. Sickness behaviour is typically what occurs in sepsis an flu - no hint of faking it.