Non-specific markers of neurodevelopmental disorder/delay in selective mutism--a case-control study.

Selective mutism (SM) in children is frequently associated with language disorder/delay suggesting that neurobiological factors may be involved in the development of SM. Motor co-ordination problems, reduced optimality pre- and perinatally and minor physical anomalies represent other markers for neurodevelopmental disorder/delay. The present study explores these markers in referred children with SM (n=54), non-referred matched controls (n =108) and in SM subgroups with and without a communication disorder (CoD). Children with SM differed significantly from controls in parent-reported motor developmental delay, and they obtained a higher pre- and perinatal "reduced optimality score". They scored significantly lower on a motor performance test and showed a higher frequency of minor physical anomalies compared with controls. There were no differences in these respects between SM and CoD compared with SM without CoD. The results confirm that neurobiological factors may be involved in the development of SM. Accordingly, the clinical assessment of referred children with SM should include a thorough history of motor development and an evaluation of present motor skills. The interplay of shyness/social anxiety and motor function problems has to be addressed to reduce misunderstandings of the child's behaviour and to adjust demands for motor skills to the actual level of the child.