The relationship between tics, OC, ADHD and autism symptoms: A cross- disorder symptom analysis in Gilles de la Tourette syndrome patients and family-members

• The relationship between tics, OC, ADHD, and autism was explored in a sample of Gilles de la Tourette's patients and their family members.
• Exploratory Factor Analyses (EFA) using quantitative symptom scales were performed to explore symptom factors both within and across symptom dimensions, using a multi-step factor analytic approach.
• EFA revealed a five factor structure partly in line with traditional symptom categories, and partly cutting through diagnostic categories.
• The 5 factorial phenotypic structure found might be more closely reflect underlying shared etiologies than the mostly used diagnosis-oriented approach

Gilles de la Tourette's syndrome (GTS) is a disorder in which obsessive-compulsive (OC), Attention Deficit Hyperactivity Disorder (ADHD) and autism symptoms occur in up to 60% of patients, suggesting shared etiology. We explored the phenotypic structure of tic, OC, ADHD, and autism symptoms as measured by the YGTSS,Y-BOCS,CAARS and AQ, in 225 GTS patients and 371 family members. First, Confirmatory Factor Analyses (CFA) were performed on the symptom structure of each separate symptom scale. Second, the symptom dimensions derived from each scale were combined in one model, and correlations between them were calculated. Using the correlation matrix, Exploratory Factor Analyses (EFA) were performed on the symptom dimensions across the scales. EFA revealed a five factor structure: tic/aggression/symmetry; OC symptoms/compulsive tics/ numbers and patterns; ADHD symptoms; autism symptoms; and hoarding/inattention symptoms. The results are partly in line with the traditional categorical boundaries of the symptom scales used, and partly reveal a symptom structure that cuts through the diagnostic categories. This phenotypic structure might more closely reflect underlying etiologies than a structure that classically describes GTS patients according to absence or presence of comorbid OCD, ADHD and autism, and might inform both future genetic and treatment studies.