Inflammation is the New Black

Big Thanks to Allyson for this article.   It's pretty good data, although I disagree with the conclusion.

There Might Be A Link Between Inflammation And Suicide Attempts

Previously, scientists had linked suicidal feelings to the kind of bodily inflammation that occurs during illness or stress, but they weren't able to explain how inflammation could translate to depression, hopelessness and a desire to kill oneself.
The new study of 100 Swedish patients finds that the higher the level of quinolinic acid in the spinal fluid, the stronger their desire to commit suicide.
"The sicker the patient, the higher the quinolinic acid," Brundin told LiveScience.

It is a neurotoxin.  But it may or may not produce depression. 

The vast majority of quinolinic acid is produced by immune cells:  microglia and macrophages. This production is increased during an immune response.
High levels of quinolinic acid are a sign of Infection or Allergy.    Those are causes of an immune reaction.
These guys are measuring effects.

This data indicates Depression is caused by an illness.