At the very heart of EMTICS stand two largescale multicentre longitudinal cohort studies, entitled ONSET and COURSE.

ONSET is a 3 year longitudinal observational study using clinical and laboratory assessments in a high-risk sample of 500 children at the age from 4-10 years. They are characterised as first-degree relatives (siblings or offs-spring) of patients with a chronic tic disorder, but have not manifested tics or obsessive compulsive symptoms at the time of study enrolment. Exposure to pharyngeal GAS carriage or infection and information on other environmental factors will be collected.

COURSE is a one year longitudinal observational study of a paediatric and adolescent population (700 children at the age from 5-16 years) with an already diagnosed chronic tic disorder, in which the course of symptom severity and occurrence of exacerbations will be linked to environmental adversities (exposure to pharyngeal GAS carriage or infection and psychosocial stressors).