Objective: The effectiveness of cognitive-behavioral therapy (CBT) for anxiety disorders in children with autism spectrum
disorders (ASD) was examined, and compared with children without ASD. Method: Children with ASD and comorbid anxiety disorders
(n = 79, 58 boys; Mage = 11.76) and children with anxiety disorders (n = 95, 46 boys; Mage = 12.85), and their parents, participated.
All families were referred to 1 of 7 mental health care centers and received the same CBT. Anxiety, quality of life, ASD-like
behaviors, and emotional-behavioral problems were measured at waitlist (ASD-group only, n = 17), pretest, posttest, and 3
months, 1 year, and 2 years after CBT. Results: CBT was more effective than waitlist for treating anxiety disorders (d = −1.45)
and anxiety symptoms (d = −0.48) in children with ASD. At 2 years follow-up, 61% of the children with and 64% without ASD
were free of their primary anxiety disorder (percentages not significantly different). The decrease in severity of anxiety
disorders after CBT (d values ranging between −1.05 and −1.46) was not different for children with and without ASD. Improvements
were less in children with ASD for (only) 2 out of 7 continuous outcomes measures: anxiety symptoms (d values ranging between
−0.68 and −0.94 vs. d values ranging between −0.98 and −1.25) and quality of life (d values ranging between 0.39 and 0.56
vs. d values ranging between 0.77 and 0.98). Conclusions: CBT for anxiety disorders is effective for children with ASD, also
in the long-term. Treatment gains may be somewhat less compared with children without ASD.