Hyperactivity, low attention span, and impulsive behaviour characterise the syndrome known as hyperkinetic disorder, or HKD for short. It is one of the most common mental disorders diagnosed among children, say the authors.
The Danish research team compared the birth records of 834 children with confirmed HKD with those of 20,100 children with no mental disorders. All the children were born between 1980 and 1994.
Children born at between 34 and 36 weeks were around 70% more likely to develop the disorder than children born at term. Babies at born below 34 completed weeks were almost three times as likely to develop the disorder.
Low birthweight babies born at term were also at risk, the study showed.
Babies born at term, but weighing 1500 to 2499 g at birth were 90% more likely to develop HKD, while those weighing between 2500 and 2999 g were 50% more likely to develop the disorder than babies weighing over 2999 g at birth.
Of the 834 children with confirmed HKD, nine out of 10 were boys. The age at which the children were diagnosed ranged from 2 to 18 years.
Single parenthood, social and economic deprivation, and young age at parenthood were all risk factors for HKD, but the results still held true even after these had been taken into account and the figures adjusted accordingly.