Chronic depression or dysthymia, despite groznost its name, is a form of mild depression. Feature is its duration and persistence of expression of the essential symptoms. To date, it is not known what may be a precipitating factor dysthymia, but particularly among others emit chemical changes in the brain caused by a decrease in serotonin levels. Serotonin – a substance that appears as a result of amino acid metabolism. In the brain, the substance acts as a neurotransmitter, but getting into the blood, acts as a so-called “hormone of happiness” to help cope with stress.