Infection was a major cause of death in early human history.Surviving those infections determined which genes were passed to the next generation.They suspect that depression helped people, especially children, survive infection.Fatigue leads to inactivity and less social contact which helps keep infection from spreading.Shunning food helps avoid food sharing which can also spread infection.Sleeplessness, which is associated with both depression and immune system activation,may have been a mechanism to keep a person alert to fight off predators after injury.If scientists are correct about this link, it could lead to new treatments for depression.They are interested in drugs that treat conditions where the immune system attacks the person's own body, known as auto immune diseases.It is possible that medications known to treat auto immune disease may be successful intreating depression also.
