08 September 2016

How the Immune System can Control Your Behavior

If someone you love is experiencing depression or finding less pleasure in social activities, you might want to look deeper.   It is quite possible that hidden infection or inflammatory condition may be causing the changes you observe.  Have compassion...there is often more to it than meets the eye.  I have seen many relationships crumble when one person is suffering from immune dysfunction and social isolation and the other does not see the illness for what it really is.

Our immune system is a powerful force inside each one of us!  This protective system is charged with the job of responding to foreign invaders to keep us in optimal health.  Most of us don't think too much about this system until it is not working correctly.  I treat many patients that suffer from overactive or under-active immune systems due to chronic infections, like tick-borne diseases;  toxic exposures, like mold and mycotoxins; or autoimmune diseases, like multiple sclerosis, lupus or Hashimoto's thyroiditis.  Although many patients understand the important role of the immune system in protection and defense, few people know that it also controls our behavior.  A recent study in Nature discussed the role of cytokines activated when the immune system goes on red alert and the connection to social isolation and autistic behaviors.  It's even plausible that changes in immune function may lead to personality changes!

Sickness and Depression

Perhaps no connection has been more studied than that of immune activation and inflammation and the link to depression.  Systemic infections cause the patient to allocate limited resources, conserve energy and prevent spread of infection.  The resulting sickness behavior is common to most infections, including viruses, bacteria and multi-cellular parasitic infections.  There is a broad spectrum of symptoms – fever, nausea, decreased appetite, malaise, fatigue and achiness – all of which may aid in the fight to conserve resources and increase isolation-type behavior.  In animal models we see sickness associated with a decrease in time  seeking interaction with a other animals as a result of diminished motivation for social exploration.  Symptoms of depression appear after pro-inflammatory cytokines are produced by the body or if they are administered experimentally. The fact that inflammation often leads to later depression suggests a cause–effect relationship.  It indicates that immune activation can precipitate depression. Many symptoms of inflammation-induced depression overlap with sickness behaviors, including fatigue, changes in sleep pattern, lack of interest in daily or pleasurable activities (anhedonia), changes in appetite or body mass and unexplained aches and pains

Inflammatory Cytokines and the Brian

A recent article about inflammatory cytokines and brain signaling discussed inflammation and the brain:
When considering the pathological signaling cascades in immunological disorders of the brain, certain cytokines might be considered of key importance, with their presence determining the course of a particular disease. Interleukin-1 (IL-1), IL-6, IL-17, and TNFα are critical for the pathogenesis of inflammation in certain brain disorders. Targeting these cytokines or their receptors can alter the course of several neurological diseases, but the effects may be beneficial or harmful.
We understand from this article that the inflammatory signals of the immune system (cytokines) have a profound effect on the brain.  Many patients battling systemic inflammatory or autoimmune disorders suffer from an "inflamed brain" and all that goes with it... symptoms like depression, anxiety and insomnia.  The role of cytokines on behavior can be summarized by saying that TNFα (sickness and depression) and IL-1β (sickness) alter behavior by direct actions on neurons of the brain.

Gaba may affect the immune system too...

GABA, an inhibitory neurotransmitter in the brain, has a similar inhibitory effect on the immune system. Antigen presenting cells (APCs) of the immune system have gaba receptors and therefore, gaba can directly inhibit the function of these immune cells. What this means is the neurotransmitter from the brain may have a direct inhibitory effect on the body's immune system.  This article on Gaba and the immune system states....Intricate and reciprocal regulatory relationships exist between the nervous system and the immune system, mediated in part by chemical messengers.


Insults to the body, from the outside or from the inside, activate cells of the innate immune system.