Adults tested for ADHD symptoms in huge study
In the largest ever study of ADHD symptoms in adults, 85,000 blood donors will help scientists figure out if the disorder is hereditary.
The number of children who have been officially diagnosed with ADHD has skyrocketed in the past decade.
Now researchers have set out to examine if symptoms such as hyperactivity, disorganised thoughts and impaired concentration are as common in these children’s parents’ generation.
“ADHD is not a children’s disease that you outgrow, but it’s a disease you can learn to live with. It is estimated that about five percent of adult Danes have ADHD, but less than one percent of them have been diagnosed,” says Kristoffer Burgdorf, a postdoc fellow at the Copenhagen University Hospital.
”Some learn to control their hyperactivity with age, but as adults they may still find it difficult to focus on tasks. They may need to leave work meetings early and generally find it difficult to keep still. They may also be more depressed or anxious than others.”
Blood donors tested for ADHD symptoms
To find out how many Danish adults have ADHD symptoms, Burgdorf and colleagues have set up a unique study, which not only quantifies the prevalence of ADHD in adults, but may also provide answers to whether the disorder is genetically determined.
The researchers have designed questionnaires, which 85,000 Danish blood donors filled in after donating blood. The questionnaire includes questions about their everyday behaviour and features of their mental state that may indicate ADHD symptoms.
The 85,000 participants also form part of the Danish Blood Donor Study, which is a scientific study of public health in Denmark.
”The questionnaires can give us an indication of what percentage of the healthy Danish average population has ADHD symptoms, but we are not using the questionnaires to diagnose the individual participants,” explains Burgdorf.
ADHD can lead to other psychiatric diagnoses
We can also see whether those with the most ADHD symptoms have other psychiatric diagnoses such as anxiety and depression – and even whether they have been involved in more traffic accidents than others. So we have quite a few variables that we wish to examine.
Initially, the researchers are interested in finding out whether there are any social factors that characterise the participants who disploy the most signs of having ADHD.
”By comparing their answers with the data we have about them from Denmark’s national registers, we can see what problems ADHD symptoms can give in adult life, with regards to e.g. job and family,” he says.
”We can also see whether those with the most ADHD symptoms have other psychiatric diagnoses such as anxiety and depression – and even whether they have been involved in more traffic accidents than others. So we have quite a few variables that we wish to examine.”
Genome sequencing may reveal whether ADHD is hereditary
In the next stage of the study, the researchers will use the questionnaires to find answers to the fundamental question: is ADHD hereditary?
Up to now, no gene variants have been found that really fit the bill in terms of ADHD, but with the size of our study, we hope we can make a breakthrough in this research field.
Every time the participants in the Danish Blood Donor Study donate blood, Burgdorf and his colleages receive a subsample, which they use to sequence parts of the participants’ genome.
By comparing the genetic analysis with the answers in the questionnaires, the researchers can see if those who have many ADHD symptoms also have some special genetic variants that those with no signs of ADHD lack. In this way, the researchers hope to figure out whether the diagnosis may be genetically determined.
”Up to now, no gene variants have been found that really fit the bill in terms of ADHD, but with the size of our study, we hope we can make a breakthrough in this research field.”
Americans to study infections and ADHD
The researchers also plan to send up to 20,000 blood samples to an American research centre, which will look for traces of past infections that may be associated with ADHD symptoms.
Scientists used to think that children with ADHD outgrew their symptoms.
This assumption has turned out to be wrong.
Children with ADHD continue to have the diagnosis as adults.
The last decade has seen a significant increase in adult ADHD diagnoses.
”There are six viruses that scientists suspect may be associated with ADHD and other psychiatric diagnoses. These include Herpes and the very common Cytomegalovirus,” says Burgdorf, adding that these are viruses that many of us have had, without them affecting our mental state.
Study goes from paper to tablets
The 85,000 Danes who participate in the Danish Blood Donor Study have already responded to a questionnaire, which they were handed in paper format when they donated blood.
Burgdorf and colleagues are currently working on a digital solution, enabling the donors to fill in the questionnaires electronically when they donate blood. This will done by means of tablets, which will be set up at the Danish blood collection stations.
”This is a very special digital platform that we are developing in collaboration with the Research Institute for Biological Psychiatry, which sees it as an opportunity to examine not only ADHD, but also the prevalence of other physical and mental disorders in the population.”
Once the three-year project is completed, the blood samples from the 85,000 participants will be stored in a bio-bank, so they can be used in the future to study the prevalence and the genetics of other physical and mental disorders.
Read the Danish version of this article at videnskab.dk