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  • About the ADHD Study


About the ADHD Study

The ADHD Study began in 2007 with the aim of acquiring new knowledge about early characteristics, developmental pathways and risk factors for Attention Deficit Hyperactivity Disorder (ADHD). This knowledge can be used to implement preventative measures and early intervention, including any treatment measures.

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The ADHD Study began in 2007 with the aim of acquiring new knowledge about early characteristics, developmental pathways and risk factors for Attention Deficit Hyperactivity Disorder (ADHD). This knowledge can be used to implement preventative measures and early intervention, including any treatment measures.

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About ADHD

ADHD is one of the most common paediatric mental health disorders, with international figures suggesting that about 5 per cent of adolescents under the age of 18 are affected. Since it is accepted to be a development disorder, signs of difficulties may be present at an early age.

Many parents of children diagnosed with ADHD at school age reported being concerned about the child's behaviour from early preschool age. They referred to babies who were difficult to soothe, restless toddlers, children who ran off as soon as they stood up and similar difficulties.

Children develop rapidly and in different ways and it is perfectly normal for children to struggle in some areas at times. For many, the problems are temporary, while others face chronic difficulties and need follow-up.

Aim of the ADHD Study

We wanted to gain new knowledge about early signs of ADHD. With this knowledge we can contribute to the early identification of children with ADHD, and to the testing of targeted preventive measures in early preschool age. Even though ADHD is partially genetically based, early measures may curb the development of symptoms and prevent the development of difficulties that often arise with ADHD.

In the ADHD study, the children are followed over time in order to look at various developmental processes related to the symptoms of ADHD and other difficulties. They were examined at both 3-years-old and 8-years-old. Data from the same children can be studied and trajectories compared in order to see why some have chronic difficulties while others grow out of them. Factors that influence development can also be studied.

The strength of the project is that we have a lot of detailed information about the children at a young age, before we knew whether they would develop ADHD or other disorders. In addition to information from clinical studies in the ADHD study, the project can also use data from the Norwegian Mother, Father and Child Study (MoBa). Some of these data were collected before the children were born.

Risk and causal factors

The reasons why some people develop ADHD are complex and differ between children. We assume that innate, hereditary and environmental factors are important for the development of ADHD.

By combining biological material and questionnaire data in MoBa with data from studies of children in the ADHD study, we can study the possible effect of genetic factors, environmental contaminants and nutrition.

Several sub-projects in the ADHD study are linked to studies of risk and causal factors in ADHD.


We needed access to data on birth, disease, development and behaviour in preschool age for many children in order to study the progression from preschool age to school age. MoBa, which had recruited over 100,000 children to be followed into adulthood, had data from pregnancy, childbirth and the first years of life. By inviting MoBa preschoolers, we were able to follow developments until school age. The ADHD study was therefore established as a MoBa sub-study.

Data collection

The ADHD study is a longitudinal follow-up study.

We wanted to include as many children as possible with the risk of developing ADHD. Children who scored high for questions about typical ADHD behaviour in the MoBa 3-year questionnaire were invited to participate in examinations in Oslo. We also invited children where the parents said that the child had been referred for hyperactivity or attention difficulties. In addition, we invited a random selection of children from the entire MoBa cohort to be a control group.

The children participated in a day study at the ADHD study's premises at Oslo University Hospital when they were all approximately 3 years old. Together with a parent, they participated in psychological testing, examination of motor skills and observation of play. The parent participated in an interview about the child's behaviour and mental health problems, and we added our own questionnaires for parents and for the educational manager in the childcare centre. After all the examinations were completed, parents received feedback on the results and a written report was made. Over 1200 three-year-olds were examined in the period from 2007 to 2011.

All the children in the study were followed up in MoBa where new questionnaires were obtained when the children turned five.

When the children turned eight, the families received a questionnaire from MoBa and another questionnaire from the ADHD Study. About two-thirds of those who attended the examinations at three years answered the questionnaire at eight years. For most of these we also received a completed questionnaire from the children's teachers. In addition, about 150 eight-year-olds underwent testing, interviews and more.

Overall, this provided an opportunity to follow children from 3 years to 8 years in many areas.

In addition to following the children through the MoBa and ADHD Study questionnaires, we can follow the children through links with other health registries. We can connect to the Norwegian Patient Register and keep track of those who receive a diagnosis in the specialist health service. We can link to the Norwegian Prescription Database and follow those who are receiving medication for ADHD.

Collaborative project

The ADHD study is a collaborative project between the Norwegian Institute of Public Health and Oslo University Hospital HF. The study started in January 2008 after a pilot phase in 2007.


Over the past couple of years, the project group has received research funding from the Research Council of Norway to continue studies of the importance of environmental contaminants and maternal diet during pregnancy and child development. Health South East is funding research where we look at the development process from three to five years, and we have applied for further funding to continue this work.

Research findings from the ADHD study

Several articles have been published in international journals based on data from the ADHD study. Five doctoral dissertations have been delivered using data from the project. In addition, project staff have published numerous articles about ADHD based on MoBa data.

Most of the particles concern traits in three-year-olds with and without hyperactivity and concentration difficulties. Behavioural characteristics and test results have been studied. Some articles have also looked at child development before 3 years. We have also examined the relationship between contaminants, diet, hormones and other factors in pregnancy and the symptoms of ADHD. We are now in the process of accessing data from the ages of 3 to 8 years so that we can analyse and publish results on trajectory data.

Here is a summary of some published results:


Are high levels of the environmental contaminants such as polychlorinated biphenyls (PCB) in the mother related to ADHD in the child? We found no association between PCB levels in the mother and symptoms of ADHD, or on test results of cognitive functioning. There was a weak correlation between elevated levels of PCBs and decreased language skills in girls and more research is required.

Genetic factors

One study also looked at genetic factors. We found no genetic markers and we assume it is related to uncertainty about diagnosis at such an early age and that our study groups too small for this type of analysis.

Language function

Nina Rohrer-Baumgartner's doctorate dealt with the language function of three-year-olds with ADHD symptoms. We know that schoolchildren with ADHD often have delayed language development and other language difficulties, but these often go undetected because the children are restless and unconcentrated. In the ADHD study, we found that preschool children with high scores on ADHD symptoms have an increased risk of language delay. This can be detected early through specific tests and mapping using questionnaires. Several combined methods of investigation are necessary. The findings emphasise the importance of a thorough study of language function in addition to the examination of symptoms in young children.

Cognition and behavioural regulation

In Annette Holth Skogan's doctorate, she looked at the executive functions of the three-year-olds in the ADHD study. Self-control and the ability to regulate behaviour develop as children grow and develop yet we know children with ADHD struggle with these skills. How early can we see if children are struggling? Through tests and questionnaire data, we found that even at the age of 3.5, it was possible to spot these traits in children, although they are not fully developed. We also found that many children with high scores on ADHD symptoms showed signs of delayed or impaired skills in these areas. Limited impulse control most clearly distinguished children with symptoms of ADHD from children with many symptoms of behavioural difficulties or children with typical development.

Behavioural difficulties

In her doctoral dissertation, Bothild Bendiksen looked at the relationships between ADHD and behavioural difficulties in preschool children. Two types of behavioural problems often occur with ADHD: oppositional behavioural disorder and severe behavioural disorder. The first is characterised by defiance, outbursts of anger and arguing, while the latter is characterised by more norm-breaking and aggressive behaviour, such as lying, stealing, picking fights or hitting others, etc. We found that oppositional behavioural problems were more common among preschool children with ADHD than the more severe behavioural difficulties.

Emotional regulation difficulties

In Kristin Romvis Øvergaard's doctoral thesis, she looked at the anxiety and regulation of emotions both in the three-year-olds and also the relationship even earlier in pre-school age. In the ADHD study, we found that many preschool children with several ADHD symptoms also had anxiety and many had difficulty regulating their emotions compared to other children of the same age. We also found that signs of anxiety and emotional regulation difficulties were present even when the children were 18-months-old, and that such early signs appeared before similar difficulties at three-years-old.