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### Clinical and neuropsychological studies  The effects of comorbidities on a variety of measures was examined in TS children and adolescents \citep{25631951}. Compared to age-matched controls the TS group did significantly worse on the parent-rated Social Responsiveness Scale which measures social skills impaired in autism. They also took significantly longer to complete forms of the Trail Making Tests. However, of the 31 TS subjects, 11 had OCD, 18 had ADHD and 9 had an anxiety disorder. Once these co-occurring conditions were taken into account, the group differences on the Trail Making Tests and the Social Responsiveness Scale were no longer significant. This study demonstrates the need for studies to includesufficient  sample sizes so that it can be determined adequate to determine  to what extent results are due to TS or to the associated comorbidities. It is well established that many factors affect tic frequency. Two recent studies examined the effects of attention on tic frequency and the results have implications for how treatment protocols could be modified to increase effectiveness. The role of attention on tic frequency was examined under several conditions \citep{25185800}. In the first study mean tic frequencies were significantly higher for 12 TS subjects compared to baselines when they were alone in a room. Then they were recorded while looking at themselves in a mirror. A second study was performed to determine whether the increase in frequency was due to increased attention to the tics themselves or due to increased self-awareness in general. In addition to the conditions from the first study, the 16 subjects were also shown videos of themselves while they were not ticcing. Tic frequency was again lower during the baseline compared to the mirror condition. Tic frequency was lower when subjects were watching the video of themselves while not ticcing. The authors suggest that future treatments stress attention to states when patients experience fewer tics. Another study of TS adults \citep{25486384} compared tic frequency while subjects were engaged in tasks that involved attending to particular fingers, colored circles, or whether a tic had occurred during a specific 2-second interval during tic suppression or free ticcing conditions. Not surprisingly, more tics were seen during a baseline free ticcing condition. During the attention tasks, tic frequency was greatest while they focused on their tics, decreased on the color attention condition, and decreased further on the finger attention condition. When subjects suppressed their tics, they reduced their baseline tic frequency similarly across all attention conditions. The results are consistent with the idea that internally-directed attention, especially with focus on tics, may contribute to momentary tic severity. The report's authors also suggested that behavioral treatment might be more effective if it focused on teaching patients to focus on external events and voluntary actions when they are in situations that are most likely to result in ticcing.