Pierre Janet proposed a diathesis-stress model of dissociative disorders and presumed as causes, first, basic disturbances – “stigmata” – as symptoms reflecting a fundamental vulnerability, and, second, accessory disorders like “fixed ideas” as effects of traumatic experiences. The main or most basic disturbance of dissociative disorders is a weakening in the ability to perform mental synthesis. Most modern approaches are congruent with Janet’s views that during traumatic experience there is a lowering of “mental strength,” that is, pathogenic associative learning processes prevent the synthetic processing of the trauma. The method of “psychological analysis” is appropriate not only for the treatment of dissociative disorders but also for the therapy of psychasthenia, because both maladaptation disorders cause a weakening in the psychic constitution. Jean-Martin Charcot noted that the success of a therapy depends to a considerable extent on mental hygiene, and that it has as an aim, among others, to eliminate pathogenic thoughts, images, or presentations.