Low autonomic arousal as vulnerability to externalising behaviour in infants with hostile mothers.

Maternal psychopathology and the child's autonomic nervous system functioning are risk factors for aggressive behaviour later in life. While research has shown that maternal psychopathology already affects young children, less is known about the association between autonomic functioning and aggressive behaviour in young children. In addition, maternal psychopathology and autonomic nervous system functioning may interact to determine the risk of aggressive behaviour. In a sample of 375 infants and their mothers, maternal psychiatric symptoms were assessed with the Brief Symptom Inventory and toddler aggressive behaviour with the Child Behaviour Checklist. Infant heart rate was recorded at 14 months. Maternal psychiatric problems, including hostility and depression, were associated with toddler aggressive behaviour. Maternal psychiatric problems interacted with mean heart rate (P=0.01) and HF variability (P=0.03) in their effect on toddler aggressive behaviour. Mothers with high psychiatric problems, in particular, high hostility, were more likely to have toddlers with high aggressive behaviour. Moreover, in the presence of maternal risk factors, low autonomic arousal renders children particularly susceptible to aggressive behaviour.