Coprolalia - Prevalence

Prevalence

Only about 10% of Tourette's patients exhibit coprolalia, but it tends to attract more attention than any other symptom. There is a paucity of epidemiological studies of Tourette syndrome; ascertainment bias affects clinical studies. Studies on people with Tourette's often "came from tertiary referral samples, the sickest of the sick". Further, the criteria for a diagnosis of Tourette's were changed in 2000, when the impairment criteria was removed from the DSM-IV-TR for all tic disorders, resulting in increased diagnoses of milder cases. Further, many clinical studies suffer from small sample size. These factors combine to render older estimates of coprolalia—biased towards clinical populations of the more severe cases—outdated. An international, multi-site database of 3,500 individuals with Tourette syndrome drawn from clinical samples found 14% of patients with Tourette's accompanied by comorbid conditions had coprolalia, while only 6% of those with uncomplicated ("pure") Tourette's had coprolalia. The same study found that the chance of having coprolalia increased linearly with the number of comorbid conditions: patients with four or five other conditions—in addition to tics—were four to six times more likely to have coprolalia than persons with only Tourette's. One study of a general pediatric practice found an 8% rate of coprolalia in children with Tourette syndrome, while another study found 60% in a tertiary referral center (where typically more severe cases are referred). A more recent Brazilian study of 44 patients with Tourette syndrome found a 14% rate of coprolalia; a Costa Rican study of 85 subjects found 20% had coprolalia; a Chilean study of 70 patients found an 8.5% rate of coprolalia; older studies in Japan reported a 4% incidence of coprolalia; and a still older clinical study in Brazil found 28% of 32 patients had coprolalia. Considering the methodological issues affecting all of these reports, the consensus of the Tourette Syndrome Association is that the actual number is below 15 percent.