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Aggression in young children often caused by nervous system defects and problems experienced by the mother during pregnancy

Young children exhibit more aggressive behaviour if their nervous system fails to respond adequately to stress situations and if they are exposed to risk factors such as smoking or psychological problems experienced by the mother during the pregnancy. This is the conclusion of PhD candidate Jill Suurland. PhD defence 4 July.

Factors in aggressive behaviour

Fighting, deliberately hurting others and responding angrily to upsets or frustrations: some children exhibit signs of problem behaviour even in early childhood. Child specialist Jill Suurland studied the neurobiological, emotional and cognitive factors affecting aggressive behaviour in young children. 

Disrupted nervous system

Her research shows that these children have difficulty regulating their impulses and negative emotions such as anger and frustration. The coordination within the autonomous nervous system of these children is disrupted: the sympathetic and parasympathetic nervous systems do not interact properly. As a reaction to stress, the sympathetic nervous system raises the breathing rate and the heartbeat. This is generally matched by a reduction in the activity within the parasympathetic nervous system, which ideally is more active during periods of rest and lowers the heart rate and breathing. But this mechanism is faulty in these children; both the sympathetic and the parasympathetic nervous systems are active or inhibited at the same time.  

Problems of the pregnant mother

Suurland discovered that these children exhibit problem behaviour particularly in combination with negative influences from the pregnant mother, such as smoking, psychological problems and a high level of stress resulting from financial worries or the lack of social support. This insight is important for early and adequate treatment of these children, she emphasises. Disproportional aggression in early childhood raises the likelihood of poor school performance, criminal behaviour and depression at a later age. Suurland calls for better identification of pregnant women with a high-risk profile so that they can be given help in the form of preventive intervention programmes. 

More research needed

According to Suurland, more research is needed because it is still not known to what extent treatment of the mother during pregnancy and of the baby during its early life influences the physiological self-regulation of the child. Focused and early intervention is in her opinion crucial. 'Persistent aggressive behaviour in older children and adolescents is often difficult to treat with the intervention programmes currently available.'

Long-term study among large group of children

Suurland studied the development of a large group of young children in the Mother-Infant NeuroDevelopment Study in Leiden. This is a longitudinal study in which 275 pregnant women and their children are monitored until the children reach the age of 3 1/2. During their pregnancy the women were screened for the presence of a large number of risk factors.The emotional and cognitive predictors of aggressive behaviour were also studied in 855 pre-school children.

In babyhood, the maturing of the autonomous nervous system lays the foundation for healthy emotional and cognitive self-regulation. This is the ability to control and manage one's own physiological, emotional and cognitive processes. A lack of self-regulation plays an important role in the development of aggressive behaviour, and in this period the nervous system is highly sensitive to environmental influences.