Sickness behaviour is a concept that's often referred to in relation to MECFS. I want to see what people think of it. Whether there's something in it, or whether its just a tool used by the mind-over-body crowd. Here's a rough intro to the concept: Sickness behaviour refers to the behavioural changes that occur when someone is ill with an infection. Strictly speaking, the term describes behaviours - like excessive sleeping, inactivity, not eating - but nowadays its usually understood to include the psychological states presumed to underlie those behaviours (e.g., depression, fatigue, pain, loss of appetite). At the core of sickness behaviour is the idea that these behaviours are adaptive. The inactivity serves to conserve the person’s energy resources for fighting infection, and the hypersomnia and anorexia might serve a similar purpose. Recently, it has also been suggested that these behaviours might serve a social purpose: to prevent others in the social group from getting infected. Some researchers have argued that, if the behaviours are adaptive, then they are likely to be centrally coordinated- for example, via a mechanism within the central nervous system. Sickness behaviour occurs following the release of pro-inflammatory cytokines. But the cytokines aren’t seen as directly causing the sickness behaviour. The idea is that the brain plays a crucial mediating role. The cytokines influence brain function, and it is the brain that regulates behaviour. So this is fundamentally different from say, being unable to move or eat because of organ failure or systemic illness (e.g. severe blood loss). In those examples, the limit is imposed by those other bodily systems, not by the brain. In the case of ‘sickness behaviour’ the idea is that there is no physical limitation of this kind – the organism makes a "decision" to invoke these behaviours when appropriate, and the brain is crucially involved in this decision. I'll come back later and try to explain some of the findings that have been used to support the sickness behaviour concept. But feel free to pitch in if you have any thoughts.