Background: Selective Mutism (SM) is an anxiety disorder with a consistent difficulty to speak in certain social situations, whereas this difficulty is not present in other situations such as the...Show moreBackground: Selective Mutism (SM) is an anxiety disorder with a consistent difficulty to speak in certain social situations, whereas this difficulty is not present in other situations such as the home environment. Regarding the different mechanisms underlying Selective Mutism, the physiological component is largely unknown. However, this information can provide insight into the underlying mechanisms of children with SM. Method: The present study compared 27 children with SM (M = 5.11 years) and 40 typically developing children (M = 5.35 years) during a rest phase and two phases of a social interaction task. In both groups physiological arousal was measured using the BIOPAC acquiring system deriving two parameters, mean heart rate (HR) and mean heart rate variability (HRV). Results: Children from the SM-group experienced higher HR during rest (F (1,63) = 5.63, p = .021) and recovery (F (1,64) = 5.19, p = .026; F (1,62) = 8.74, p = .005) compared to typically developing children. Second, children from the SM-group experienced lower HRV during performance (F (1,65) = 4.47, p = .039; F (1,62) = 4.28, p = .043) and recovery (F (1,64) = 4.22, p = .044; F (1,62) = 5.10, p = .028) compared to typically developing children. Discussion: Current research replicates and extends research in children with SM. The findings from HR and HRV indicate a prolonged stress response in children with SM in different (social) situations. Children with SM seem to be limited in their ability to adapt their physiological responses in HR and HRV to the situation. The results seem to suggest an overactive sympathetic autonomic nervous system in children with SM.Show less
