use. Insidious onset may reach back as far as can be remembered, or it may begin with smaller episodes of lesser severity that become gradually stronger. Patients with drug-induced depersonalization do not appear to be a clinically separate group from those with a non-drug precipitant. Relation to other psychiatric disorders Depersonalization exists as both a primary and secondary phenomenon, although making a clinical distinction appears easy, it is not absolute. The most common comorbid disorders are depression and anxiety, although cases of depersonalization disorder without symptoms of either do exist. Comorbid obsessive and compulsive behaviours may exist as attempts to deal with depersonalization, such as checking whether symptoms have changed and avoiding behavioural and cognitive factors that exacerbate symptoms. Many people with personality disorders such as schizoid personality disorder, schizotypal personality disorder, and borderline personality disorder will have high chances of having depersonalization disorder. History The word depersonalization itself was first used by Henri Frédéric Amiel in The Journal Intime. The 8 July 1880 entry reads: Depersonalization was first used as a clinical term by Ludovic Dugas in 1898 to refer to "a state in which there is the feeling or sensation that thoughts and acts elude the self and become strange; there is an alienation of personality – in other words a depersonalization". This description refers to personalization as a psychical synthesis of attribution of states to the self. Early theories of the cause of depersonalization focused on sensory impairment. Maurice Krishaber proposed depersonalization was the result of pathological changes to the body's sensory modalities which lead to experiences of "self-strangeness" and the description of one patient who "feels that he is no longer himself". One of Carl Wernicke's students suggested all sensations were composed of a sensory component and a related muscular sensation that came from the movement itself and served to guide the sensory apparatus to the stimulus. In depersonalized patients, these two components were not synchronized, and the myogenic sensation failed to reach consciousness. The sensory hypothesis was challenged by others who suggested that patient complaints were being taken too literally and that some descriptions were metaphors – attempts to describe experiences that are difficult to articulate in words. Pierre Janet approached the theory by pointing out his patients with clear sensory pathology did not complain of symptoms of unreality, and that those who have depersonalization were normal from a sensory viewpoint. Psychodynamic theory formed the