2016 Gatlinburg Conference Poster
PS-71
Title: Predictors of Specific Phobia in Children with Williams Syndrome: Behavioral Regulation and IQ
Authors: C. Holley Pitts, Bonita P. Klein-Tasman, Jason W. Osborne, Carolyn B. Mervis
Introduction: The prevalence of Specific Phobia (SP) in children with Williams syndrome (WS) exceeds 50% in several published
studies. To consider the effects of possible predictors on the probability that a child with WS would be diagnosed with SP, a
logistic regression analysis was conducted with age, sex, IQ, and behavioral regulation difficulties as possible predictors.
Methods: Participants were 193 children with WS (100 girls, 93 boys) aged 6.01 - 17.98 years (M: 10.71, SD: 3.39). The Anxiety
Disorders Interview Schedule: Parent was administered to determine if the child met DSM-IV diagnostic criteria (including
interference and impairment) for SP. Child intellectual abilities were measured by the Kaufman Brief Intelligence Test-2 IQ (M:
73.84, SD: 14.78). Behavioral regulation was measured by the Behavioral Regulation Index (BRI) T-score on the Behavior Rating
Inventory of Executive Functioning-Parent (M: 63.20, SD: 10.59; general population M: 50, SD: 10). Higher T-scores indicate
greater difficulties. T-scores at or above 65 are considered clinically elevated.
Results: Diagnostic criteria for SP were met by 56% of the children. To evaluate possible predictors of the probability of receiving
a SP diagnosis, a blockwise logistic regression was conducted. Presence of SP diagnosis was the dependent variable. In step 1, the
effects of age and sex were evaluated. The predictors significantly improved model fit (null -2LL = 268.81, step 1 -2LL = 257.88,
2(2) = 6.93, p < .031). As age increased, the probability of havingSP decreased (p < .01). No sex differences were detected (p <
.30). The linear effects of IQ and BRI T-score were entered in step 2 and significantly improved model fit (-2LL = 240.48,
 2(2) =
17.40, p < .0002). Possible quadratic effects of IQ2 and BRI T-score2 were examined in step 3. Entry of IQ2 did not yield a
significant improvement in model fit (-2LL = 238.67, p < .18). To improve model specification, the nonsignificant effect of IQ2 was
removed. When BRI T-score2 was entered into the equation, model fit significantly improved (-2LL = 233.08,
2(1) = 7.40, p
.007). In the final model, a significant linear effect of IQ (p = .005), a linear effect of BRI T-score (p < .002), and a quadratic effect
of BRI T-score (p < .01) was detected. As IQ increased, the probability of receiving a SP diagnosis decreased. When converted to
conditional probabilities, results indicated that, after controlling for BRI T-score, age, and sex, a child with an IQ of 52 had an 83%
chance of receiving a SP diagnosis whereas a child with an IQ of 96 had a 52% chance. After controlling for IQ, age, and sex, the
probability of being diagnosed with SP initially increased as BRI T-scores increased. However, the probability began to asymptote
at a high level when BRI T-scores reached the clinical range. A child with a BRI T-score of 50 had a 37% chance of receiving a SP
diagnosis whereas a child with a BRI T-score of 65 had a 72% chance and a child with a BRI T-score of 76 had a 71% chance.
Discussion: As age increased, prevalence of SP decreased. After controlling for behavioral regulation difficulties, children with
lower IQs were more likely to meet criteria for SP. The curvilinear effect of BRI T-score revealed that, after controlling for IQ, the
probability of being diagnosed with SP gradually rose as behavioral regulation difficulties approached the clinical range. Once the
clinical range was reached, the probability of receiving a SP diagnosis leveled off at a high level. Implications of these findings will
be considered.
Funding: NICHD R37 HD29957, NINDS R01 NS35102, Williams Syndrome Association WSA-0104.