a result, an additional six subjects were excluded (Figure 1). A total of 267 subjects had no IQ, autism, ID, or SEN statement data available. These subjects were no more likely to receive subsequent tic diagnoses compared with subjects in the main sample and thus were included in the overall analysis (data not shown). Controls were defined as subjects who were eligible for analysis (data available at age 13 and not excluded based on the presence of ID, autism, IQ <80 or an SEN statement in the absence of available IQ data), but did not meet any of the tic case definitions.
