Tourette syndrome and comorbid early-onset schizophrenia

A study of the shared phenomenology between Tourette syndrome (TS) and schizophrenia.

An illustrative case report is presented. We used a chart review of 399 clinically ascertained patients with TS to identify 10 cases meeting criteria for schizophrenia. From our 10 patients, salient clinical characteristics were then tabulated. We then extracted similar clinical characteristics from a previously published series of patients with comorbid TS and schizophrenia in order to combine cases and allow for a comparison between childhood-onset schizophrenia (COS), adolescent-onset schizophrenia (AdolOS), and adult-onset schizophrenia (AduOS) cases in these groups.

We found 10 cases of schizophrenia (all were males) in the 399 TS patients for a prevalence rate of 2.5% (95% CI 0.96-4.04). Mean age of tic onset for TS diagnostic criteria ranged from 2-14 years with a mean of 8.2 years. The mean age of diagnosis for schizophrenia was 14.2 (range 9-23 years). We found six cases of schizophrenia with onset of positive psychotic symptoms by 13 years of age, two cases with onset after 13 years of age and before 18 years of age, and two cases with onset after 18 years of age. Attention deficit hyperactivity disorder was present at a higher rate (70%) than one would expect in a clinically ascertained group of patients with TS. Comparison between COS, AdolOS and AduOS in our pooled cases noted a sex bias skewed toward males. Catatonic symptoms may be more likely in child or adolescent onset cases and negative symptoms more likely in AduOS cases.

The 2.5% prevalence of schizophrenia in our TS sample exceeds the 1% expected rate of schizophrenia in the general population (chi-square=9.14; P=.0025). The six cases of COS (before 13 years of age) exceeds the expected rate of 1-2 per 100,000 (chi-square=4499; P=.0001). The 752-fold increase in observed rates of comorbid TS and COS over expected rates suggests a role for unknown common underlying etiologic factors. Based on clinical features, patients with TS and comorbid COS, AdolOS, or AduOS do not have different conditions. We conclude with suggestions for further research.