 Tourette's is associated with several comorbid conditions, or co-occurring diagnoses, which are often the major source of impairment for an affected child. Most individuals with tics do not seek medical attention, so epidemiological studies of TS "reflect a strong ascertainment bias", but among those who do warrant medical attention, the majority have other conditions, and up to 50 % have ADHD or OCD. One author reports that a ten-year overview of patient records revealed about 40 % of patients with Tourette's have "TS-only" or "pure TS", referring to Tourette syndrome in the absence of ADHD, OCD and other disorders. In children with tics, the additional presence of ADHD is associated with functional impairment, disruptive behavior, and tic severity. Other comorbid conditions include self-injurious behaviors (SIB), anxiety, depression, personality disorders, oppositional defiant disorder, and conduct disorders.
