14 DAY TRIAL // It appears that the anti-social, anxious and depressed behaviors in people who are sick, have a perfectly good scientific explanation – this emotional chaos is caused by cytokines that have crossed into the brain.
Cytokines are signaling molecules released by the immune system as a response to infection and stress.
Normally, they are too large to pass through the blood-brain barrier, but according to recent studies, they can enter through naturally occurring leaky regions and specialized channels.
And if you add the fact that they can also affect nerves that transmit signals into the brain, then we can conclude that cytokines associated with inflammation can cause depression.
Andrew Miller of Emory University School of Medicine in Atlanta, Georgia, explained that “cytokines can interact with virtually every pathway relevant to depression.
“And the idea that inflammation induces behavioral changes makes evolutionary sense too, he says.
“Cytokines are trying to shut your body down so that you can devote your resources to healing.
“But at the same time, a wounded animal is a target so it needs to be hyper-alert in case a predator comes onto the scene.”
Miller came to his conclusion after imaging the brains of patients receiving interferon-alpha (an antiviral drug that releases the inflammatory cytokine) to treat hepatitis C.
The drug activated the dorsal anterior cingulate cortex – a brain region involved in error detection and conflict monitoring, triggering symptoms similar to highly neurotic people, with obsessive compulsive behavior.
“If you get increased activity in that area of the brain, people tend to be more suspicious and perhaps interpret innocent remarks as threatening,” said Miller.
Other factors that can trigger the release of cytokines besides infections and toxins, are stress and obesity.
It looks like obese people are more likely to be depressed, and the adipose tissue is a potent source of cytokines, concluded the research.
As for stress, it can trigger the immune system and affect the behavior of people who are apparently in good health.
But Naiomi Eisenberger at the University of California in Los Angeles and her colleagues, said that cytokines also have positive effects, like making some people more sensitive to social pain, after being injected with a bacterial toxin that boosts inflammatory cytokines (the IL-6 cytokine seems to especially stimulate activity in brain regions involved in empathy).
This type of findings could lead to new treatments against depression, New Scientist reports.