The intent-to-treat sample included 40 children with ASD and an anxiety disorder living in a major metropolitan area of the western United States, ranging in age from 7–11 years (M = 9.20, SD = 1.49), and their primary parents (defined as parents who were primarily responsible for overseeing the child's daily activities). Sample size was determined using a power analysis assuming a large ES for group differences at posttreatment/postwaitlist. This ES estimate was used in view of previous CBT trials for child anxiety disorders that have generated large effects (e.g. Barrett et al., 1996 (link); Wood, Piacentini, Southam-Gerow, Chu, & Sigman, 2006 ). Children were referred by a medical center-based autism clinic, regional centers, parent support groups, and school personnel such as inclusion specialists. See Figure 1 for descriptive data on patient flow through the study.
Participants met the following inclusion criteria: (a) met research criteria for a diagnosis of autism, Asperger syndrome, or PDD-NOS (see below); (b) met research criteria for one of the following anxiety disorders: separation anxiety disorder (SAD), social phobia, or obsessive compulsive disorder (OCD) (see below);1 (c) were not taking any psychiatric medication at the baseline assessment, or were taking a stable dose of psychiatric medication (i.e., at least one month at the same dosage prior to the baseline assessment), and (d) if medication was being used, children maintained the same dosage throughout the study. This study was approved by a university-based IRB. Parents gave written informed consent and children gave written assent to participate in the study.
Families were excluded if (a) the child had a verbal IQ less than 70 (as assessed in previous testing, or, if there was any question about the child's verbal abilities noted by the independent evaluator at baseline, on the basis of the Wechsler Intelligence Scale for Children-IV administered by the independent evaluator); (b) the child was currently in psychotherapy or social skills training, or was receiving behavioral interventions such as applied behavior analysis; (c) the family was currently in family therapy or a parenting class; (d) the child began taking psychiatric medication or changed his/her dosage during the intervention; or (e) for any reason the child or parents appeared unable to participate in the intervention program.
Table 1 presents descriptive information for participating families. Thirty-seven primary parents also reported their annual family income. Nine (24.3%) reported an income below $40,000; 10 (27.1%) reported an income between $40,001 and $90,000; and 18 (48.6%) reported an income over $90,000 per year.