[Introduction to chronic depression and resistant depression].

Chronic depression actually covers several different nosographic entities. Among the predictive factors for chronicity, personality disorders raise the complex issue of the relationship between traits and depression. Some approaches favour the concept of premorbid personality, others in contrast insist more on personality disorders which complicate a depressive episode. In order to account for both stress factors and biological factors in the progression of depression towards chronicity, Post suggested in 1992 a bold integrative pattern. In this pattern, the premorbid period would be marked by secondary sensitization to repeated stress factors. These factors would cause not only short-term but also longer-term fragility by modifying the transcription of protein encoding, in particular for the C-fos oncogene. This would cause peptide alterations which originate a vulnerability to mood disorders. With time, an accumulation mechanism and a kindling phenomenon would cause the initial depressive episode to develop, and that in turn would constitute a new vulnerability factor for the new spontaneous occurrence of further depressive episodes. This model has the merit to underline the importance of early and durable treatment. It also suggests a promising approach for the future.