Register-based studies of mental disorders

Introduction: Denmark has been pioneering international psychiatric register research for decades. In this article we review central publications, by Danish and international authors, based on data from the Danish Psychiatric Central Research Register and other related registers. Research topics: Our aim was to describe the history, development and achievements of psychiatric research, based on the Danish national registers. The studies considered in this review can be categorized as follows: i) health service research, mainly studies on prevalence and incidence, ii) studies on the outcome of mental disorders, iii) studies on the aetiology of mental disorders. Conclusion: Studies based on Danish registers have provided significant contributions to international psychiatric research. The major advantage of the registers is that they cover the entire population, which makes the conduction of nationwide population-based studies possible. Furthermore, all information in the registers is connected to each citizen’s unique personal identification number, which enables linkage between various registers and biobanks. Such linkage studies have provided important knowledge on the aetiology of mental disorders. Despite inherent limitations about internal and external validity, the Danish national registers have been extremely valuable to international psychiatric research and will continue to play an important role in years to come.