Impaired theory of mind and symptoms of Autism Spectrum Disorder in children with Prader-Willi syndrome.

In order to evaluate the social cognitive functioning in children with Prader-Willi syndrome (PWS), Theory of Mind (ToM) and symptoms of Autism Spectrum Disorder were evaluated. Sixty-six children with PWS aged 7-17 years were tested using the Theory of Mind test-R and the Diagnostic Interview for Social Communication disorders. We tested the correlation between Total ToM Standard Deviation Score (Total ToM SDS) and genetic subtype of paternal deletion or maternal uniparental disomy, and total IQ, verbal IQ and performal IQ. Prevalence and symptoms of Autism Spectrum Disorder were assessed. Median (interquartile range) of total ToM SDS of those aged 7-17 years was -3.84 (-5.73, -1.57). Their Total ToM SDS correlated with total IQ (β=0.662, p<0.001, adj.R(2)=0.407), in particular with verbal IQ (β=0.502, p=0.001, adj.R(2)=0.409), but not with performal IQ (β=0.241, p>0.05, adj.R(2)=0.259). No difference in Total ToM SDS was found between children with deletion and maternal uniparental disomy (β=-0.143, p>0.05, adj.R(2)=-0.016). Compared to the reference group of healthy children aged 7-12 years, children with PWS in the same age group had a median ToM developmental delay of 4 (3-5) years. One third of children with PWS scored positive for Autism Spectrum Disorder. Most prominent aberrations in Autism Spectrum Disorder were focused on maladaptive behavior. Our findings demonstrate a markedly reduced level of social cognitive functioning, which has consequences for the approach of children with PWS, i.e. adjustment to the child's level of social cognitive functioning.