Chronic illness and aggressive behaviour: A population-based study of 4-year-olds

The objective of this study was to examine the hypothesis that aggressive behaviour is explained by various medical conditions. The current study investigated this hypothesis in a population-based study of families with a 4-year-old child (n?=?1915). Maternal reports of child health and development were assessed and a paediatrician examined a subsample (n?=?263) with a chronic illness. Twice as many toddlers with a chronic physical disorder displayed aggressive behaviour when compared with toddlers without such disorders. All seven medical diagnostic categories included children with aggressive behaviour, but the highly prevalent condition of asthma contributed to more than a third of the cases with co-occurrence of chronic illness and aggressive behaviour. Neurological, sensory and skin/joint disorders accounted for another third. Subsequent analyses showed that poor language was an additional risk factor while attending day-care centres in groups with 5?–?15 children was a protective factor against aggressive behaviour.