In Europe including the Nordic countries we face a demographic development towards more elderly and fewer young adults who can contribute to the future society. We see an increase in the number of children and families in contact with the health care system for diagnosis and services for an array of childhood neuropsychiatric disorders in the Nordic countries. Further, an increasing proportion of children and youth are reporting mental and social health problems, which in the past have been predictive of poor adult welfare and wellbeing.

Poor mental health is associated with reduced educational attainment, higher school dropout rates and lower lifetime employability. Thus, it is essential from a societal and research perspective to develop an understanding of how mental health problems develop in a life course.

As individual countries, the Nordic countries are too small to have a significant influence. However, working together within research, the countries can provide more than the sum of what the individual countries can deliver. The strength of Nordic register research is well acknowledged and the most internationally scientifically recognized strength is our well-established register-based information system.

Together the three Nordic countries have the longest register follow-up by details, and in combination with the large Nordic ad hoc cohorts the Nordic countries possess a unique opportunity for examining life course trajectories and the potential to gain the added Nordic value from the early establishment of central registration of health, educational and welfare measures.

We have already established a data infrastructure to combine register data from Denmark and Finland. In Finland extensive information has furthermore been collected about the generations born in 1987 and in 1997. Two sub cohorts, each consisting of about 60,000 individuals, have been established including more specific information on their parental and family background as well as on follow-up, covering also information on welfare services, education, employment, income etc.

In Norway and Denmark the two largest ad hoc birth cohorts in the world have been established and children of these cohorts have been followed for more than 12 years. In both cohorts there has been a focus on mental child health measures. These cohorts are all linked to the registers and have already contributed at a high international level to our understanding of early life programming of mental health.