"Furthermore, while the search for causes should proceed unabated, the ultimate value of these data are their contribution to the growing awareness of child neurodevelopment problems in general and understanding of the resources needed to ensure optimal development for all children," they continued.
The authors proposed two models to explain the observed increases. One possibility is that the pattern of increase is coincidental, and that independent disease factors are causing the rise in incidence of each condition.
Alternatively, there may be one or more shared factors, such as genetics, environment, diagnostic shift, or a combination of these factors.
The authors drew on Denmark's renowned national health care data banks, linking information from the Danish Medical Birth Registry with data from the Danish National Psychiatric Register. The latter database included diagnoses recorded by psychiatrists using standardized diagnostic codes (ICD-10).