You know how you feel groggy, lazy, and unmotivated even after you come out of an illness? Do you ever find that it takes a few extra days to get back into shape? Well, it turns out that's just the aftereffects of your body shifting energy around to fight whatever illness or injury you sustained.
In a recent study published in Trends in Cognitive Sciences, researchers at Emory University explained the link between having a chronic inflammation in the body, the corresponding reduced release of dopamine in the brain, and a decrease in motivation and energy levels. The study also suggests the possibility that the body reduces the production of dopamine to optimize its energy expenditure to try and more efficiently combat the inflammation.
Dopamine is one of the so-called "happiness chemicals" that is responsible for motivation, experiencing pleasure, memory, and movement. If your body is producing enough dopamine, you'll feel energetic, optimistic, and motivated. The Emory study suggests that when the body is fighting a chronic inflammation, the body produces less dopamine. This makes the person more sluggish and less likely to spend energy on doing tasks and more energy towards healing.
Andrew Miller, co-author of the study, says, “If our theory is correct, then it could have a tremendous impact on treating cases of depression and other behavioral disorders that may be driven by inflammation. It would open up opportunities for the development of therapies that target energy utilization by immune cells, which would be something completely new in our field.”
From the News Medical article on the subject
"Recently, it was discovered that immune cells also enjoy a unique capability to shift between various metabolic states, unlike other cells. This could affect cytokine release patterns in such a way as to signal the brain to conserve available energy for the use of the immune system.
These facts were the foundation of the new hypothesis, which explains it in terms of evolutionary adaptation. In the hypothetical early environment, the immune system, faced with abundant microbial and predatory challenges, needed tremendous amounts of energy. It therefore had its own mechanism to signal other body systems, via the mesolimbic dopamine system, to control the use of energy resources during periods when the organism was undergoing severe or sudden stress.
Modern life is relatively soft and less challenging. With less physical activity, low-grade inflammation is chiefly due to factors such as obesity, chronic stress, metabolic syndrome, aging and other lifestyle illnesses. This could mistakenly cause the mesolimbic dopamine neurons to produce less dopamine. Lower dopamine levels in turn decrease the motivation for work, by reducing the perception of reward while increasing the perception of effort involved. This ultimately conserves energy for use by the immune system."
Needless to say, this discovery could have tremendous impact on studies in disease, depression, and other illnesses that affect dopamine levels. So now you know the possible cause for your post-illness blahs.