Psychopathological profile in children with Prader-Willi syndrome as compared with autism spectrum disorder

Background: Children with Prader-Willi syndrome (PWS) can present with social deficits and repetitive behaviours that are also encountered in autism spectrum disorder (ASD). This study aimed at ascertaining possible differences in psychopathology between PWS and ASD, with particular attention to obsessional thinking, repetitive behaviours, and impulsivity. Methods: 71 children, aged 4-15 years: 24 with PWS, 23 with ASD, and 24 community controls, were assessed on two standardized parent-reported questionnaires: the Child Behaviour Check List (CBCL) and the Autism Spectrum Quotient (AQ). Group differences were tested with one-way ANOVA. Results: ASD had higher CBCL internalizing symptom scores (67.50 + 9.09) than PWS (56.62 + 9.02, Cohen's d=1.20). On specific CBCL items, PWS had more obsessionality than ASD, which, in turn, showed more impulsivity than PWS. ASD had higher AQ scores than PWS, with small to medium effect sizes (d's ranging from 0.22 to 0.53). Conclusions: The PWS phenotype was characterized by intense obsessionality, more marked than in ASD. ASD had greater psychopathology than PWS, especially of the internalizing type. Although limited by the small sample size, this study identifies obsessionality as common feature in PSW. Such symptom, considering the negative impact on daily functioning, requires clinical attention for specific treatment approaches.