Depression is not a uniform clinical picture, but a group of different diseases with similar symptoms. A large part of them could be due to inflammation and could be successfully treated with anti-inflammatory drugs.
There are many connections and interactions between the immune system and the brain. Special messenger substances play a decisive role here. These so-called cytokines regulate the immune system, but also have effects on the brain and can even influence our behavior. This also explains why patients with chronic inflammatory diseases such as rheumatoid arthritis, psoriasis or Crohn's disease suffer significantly more frequently from depressive moods, loss of drive and appetite, anxiety, leaden fatigue and increased pain. If those affected receive certain anti-inflammatory drugs, their mood often improves. This relationship is confirmed in the laboratory: about one in three patients with depression has elevated inflammatory marker values such as C-reactive protein (CRP), tumour necrosis factor (TNF), interleukin 1 (IL-1) and interleukin 6 (IL-6) in the blood.
Inflammatory messenger IL-6 plays key role
The cytokine IL-6 seems to play a central role in the development of depression and many other diseases. It enters the brain through various pathways and influences structures of the limbic system such as the so-called amygdala. This is responsible for the emotional evaluation and recognition of situations, but is also associated with the development of depression. IL-6 also seems to be involved in other diseases that occur more frequently in people with rheumatism, for example cardiovascular diseases or diabetes mellitus. This theory is supported by the fact that Rheumatism therapy with so-called IL-6 inhibitors often also has positive influences on depressive symptoms and other concomitant diseases.
Different diseases - similar symptoms - a therapy?
At least in some depressive patients, the depression is probably caused by inflammation, which could be treated with anti-inflammatory rheumatic drugs. To recognize such complex relationships and to draw the right conclusions from them, however, requires a lot of experience and close cooperation between rheumatology, immunology, psychiatry, cardiology, diabetology and many very different disciplines.
