Tourette syndrome is considered a model neuropsychiatric disorder of childhood, reflecting an interaction between genetic and environmental factors, in a review of clinical characteristics, heredity and vulnerability, and neuroanatomy and neurochemistry, from the Child Study Center, Yale University, New Haven, CT. Referring to Israeli studies, the prevalence of TS is cited at 0.1% in boys and 0.01% in girls, or 1 in 1500 children; milder forms or chronic tic disorders have much higher prevalence rates of 4-6%. Most children developing tics have a history of prior hyperactivity or ADHD, and 30-60% develop OCD in preadolescence. Improvement during adulthood can be expected. TS is often familial, about 8% of relatives having TS and 17% exhibiting chronic tic disorders. Degree of severity is broad, mostly mild and only a minority showing serious functional impairment. An autosomal dominant transmission of inheritance is suggested by studies of large, multigenerational pedigrees, with higher penetrance for males than females. The search for the gene locus has been elusive, impeding research in the relative importance of genetic and environmental factors. Anatomically, symptoms of TS are related to abnormalities in cortico-striatal-thalamic-cortico pathways. Chemically, dopaminergic and serotonergic systems may be involved. 
COMMENT. This review of the history of our understanding of Tourette syndrome serves as a model of changing concepts of neuropsychiatric disorders. Initially considered among neuroses and hysterias, TS is now treated as an example of genetic, developmental disorders, with a neuroanatomical and neurochemical basis, and more recently, an autoimmune disorder. Maturational changes in symptomatology are also complicated by comorbid OCD and ADHD, and the adverse effects of pharmacotherapy, especially stimulants. Methylphenidate is perhaps the primary environmental trigger for the onset or exacerbation of TS, and may also explain the apparent increased incidence and awareness of TS during the past 30 years.
Previous reports from the Yale group of TS investigators are reviewed in Progress in Pediatric Neurology III, PNB Publishers, 1997;pp314-5.