Pediatricians, allergists and ophthalmologists are among the first to see or identify a child as having tics, although the majority of tics are first identified by the childs parents. Coughing, blinking, and tics that mimic unrelated conditions such as asthma are commonly misdiagnosed. In the UK, there is an average delay of three years between symptom onset and diagnosis. Differential diagnosis
Tics that may appear to mimic those of Tourettes—but are associated with disorders other than Tourettes—are known as tourettism and are ruled out in the differential diagnosis for Tourette syndrome. The abnormal movements associated with choreas, dystonias, myoclonus, and dyskinesias are distinct from the tics of Tourettes in that they are more rhythmic, not suppressible, and not preceded by an unwanted urge. Developmental and autism spectrum disorders may manifest tics, other stereotyped movements, and stereotypic movement disorder. The stereotyped movements associated with autism typically have an earlier age of onset; are more symmetrical, rhythmical and bilateral; and involve the extremities (for example, flapping the hands).If another condition might better explain the tics, tests may be done; for example, if there is diagnostic confusion between tics and seizure activity, an EEG may be ordered. An MRI can rule out brain abnormalities, but such brain imaging studies are not usually warranted. Measuring thyroid-stimulating hormone blood levels can rule out hypothyroidism, which can be a cause of tics. If there is a family history of liver disease, serum copper and ceruloplasmin levels can rule out Wilsons disease. The typical age of onset of TS is before adolescence.
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:

 I find myself regarding existence as though from beyond the tomb, from another world; all is strange to me; I am, as it were, outside my own body and individuality; I am depersonalized, detached, cut adrift. Is this madness? Depersonalization was first used as a clinical term by Ludovic Douglas 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.