The aim of this five-year prospective study was to follow and compare a group of children with severe sleep problems in infancy with a control group regarding development of symptoms of attention-deficit/hyperactivity disorder (ADHD). Factors in infancy were sought which were associated with development of ADHD in later childhood. A total community sample of 2518 infants aged 6-18 mo was approached with a questionnaire, and 83% responded. Data from the collection procedure point to a non-selective dropout. A case group of those children aged 6-12 mo who fulfilled specific criteria for severe and chronic sleep problems (n = 27) was compared with a control group of equal size, matched for age and gender. At the age of 5.5 y, seven of the children in the sleep problem group met the criteria for the diagnosis of ADHD based on an in-depth assessment by a multidisciplinary team. None of the control children qualified for the diagnosis. This difference is statistically significant. Comparisons between the children with ADHD and the rest of the problem group showed that given severe infant sleep problems, the following characteristics in infancy were associated with subsequent diagnosis of ADHD: psychosocial problems in the family, bedtime struggles and long sleep latency at bedtime. Owing to the small sample size, the results are considered preliminary.
Conclusion: Approximately one in four children with severe sleep problems in infancy will later qualify for the diagnosis of ADHD. Infants with severe sleep problems, especially in combination with behavioural problems, high activity level and psychosocial problems in the family, deserve attention since neurodevelopmental problems seem to be prevalent in this category of children.