**12. Conclusions**

Anxiety is a frequent co-occurring condition in persons with ASD and particularly children and adolescents with ASD. During the past decade, multiple clinical trials have demonstrated significant evidence that CBT employed to treat anxiety in children and adolescents with ASD was generally effective and clearly constituted an evidence-based intervention treatment modality. Effect sizes, while significant, ranged from small to large depending on the study and particularly on outcome measures. Virtually all of the trials reported in this chapter were relatively small with treatment samples of less than 30 participants receiving CBT. This suggests the need for larger randomized trials.
