Background: Better indicators are needed for identifying children with early signs of developmental psychopathology.
Aims: To identify measures of autonomic nervous system reactivity that discriminate children with internalising and externalising behavioural symptoms.
Method: A cross-sectional study of 122 children aged 6--7 years examined sympathetic and parasympathetic reactivity to standardised field-laboratory stressors as predictors of parent- and teacher-reported mental health symptoms.
Results: Measures of autonomic reactivity discriminated between children with internalising behaviour problems, externalising behaviour problems and neither. Internalisers showed high reactivity relative to low-symptom children, principally in the parasympathetic branch, while externalisers showed low reactivity, in both autonomic branches.
Conclusions: School-age children with mental health symptoms showed a pattern of autonomic dimorphism in their reactivity to standardised challenges. This observation may be of use in early identification of children with presyndromal psychopathology.