“…The diagnosis depends on the presence of motor and vocal tics that have their onset in childhood and are present almost daily for at least 1 year [Diagnostic and Statistical Manual of Mental Disorders, 1980,19871. There is a wide range of associated behaviors including attention deficit disorder with or without hyperactivity, obsessive-compulsive behaviors, conduct disorder, learning disabilities, stuttering, sleep disorders, inappropriate sexual behaviors, and others [Burd and Kerbeshian, 1984;Burd et al, 1987;Comings, 1987Comings, ,1989aComings, , 1990,1985, 1987aEldridge et al, 1977;Erenberg et al, 1986;Jagger et al, 1982;Burd, 1987, 1989;Ludlow et al, 1982;Mendelson et al, 1980;Nee et al, Individual Pedigrees Our first suspicion that some TS patients might be homozygous came from some individuals whose mother and father had either TS or tics and whose symptoms were particularly severe.…”