A few weeks ago, researches from all over Europe (and some even from the USA) gathered in Dublin to discuss the progress of the CoCA project. This project, investigating the prevalence and causal factors of ADHD comorbidities, is now almost half way. Time for an update on what’s happening.
ADHD is a risk factor for developing other (psychiatric) disorders
One of CoCA’s aims is to estimate the prevalence of comorbid disorders that occur together with ADHD. By using very large data registries from Norway, Sweden, Denmark and Estonia we can estimate the risk of developing a psychiatric comorbidity when a person has ADHD. For instance, last month a paper was published based on data from Norway, stating that the prevalence of anxiety, depression, bipolar and personality disorders, schizophrenia and substance use disorders is 4 to 9 times higher in adults with ADHD compared to adults without ADHD . Interesting differences between men and women were also observed in this study. Such that depression is much more prevalent in women with ADHD, compared to women without, while in men substance use disorders are more common together with ADHD.
ADHD does not only co-occur with other psychiatric disorders, but also with obesity. Earlier last year, we published a study based on the Swedish national registry, where it was observed that ADHD and being overweight or having obesity share familial risk factors . In other words, when you have a sibling who is overweight or has obesity, you are more likely to have ADHD compared to similar people who do not have overweight siblings.
The data from these registries can not only be used to estimate prevalence, but also to predict the risk someone has to develop other disorders. Our partners in the USA are using advanced machine learning tools to predict within the ADHD population who will develop comorbid disorders. Using the Swedish registry data they have found that having an ADHD diagnosis combined with a high number of injuries before the age of 12 predicts a comorbid substance use disorder at a later age. High risk taking behavior could mediate this association, and may therefore be a trait to investigate further and monitor in young people with ADHD. These data are now being further investigated and have not yet been published.
Publications on other registries and data will come out soon, so keep your eye on this blog for more information on the co-occurrence of (psychiatric) disorders in persons with ADHD.
ADHD and (psychiatric) comorbidities share genetic variants
When you know that ADHD often co-occurs with other disorders, the next question is to understand how and why. Our geneticists are trying to map the genetic overlap between the different disorders and identify shared genetic risks. Much of the work is still ongoing, but you can expect some exciting findings to be published very soon. What I can already share is the recent publication on how polygenic risk scores of ADHD overlap with other disorders and traits . Polygenic risk scores (PRS) were calculated based on 12 genetic loci that are associated with ADHD based on earlier studies. In other words, the more risk variants you have on these loci, the higher your risk is for ADHD. Using the UK Biobank data, the researchers found that ADHD PRS were associated with higher body mass index, neuroticism, anxiety, depression, alcohol and nicotine use, risk taking and lower general cognitive ability (verbal-numerical reasoning). This suggests that the genes that contribute to ADHD are also involved in other traits and disorders that are often observed in people with ADHD. More knowledge on these genetic factors is expected from the studies that are now being conducted.
Searching for new treatment possibilities for ADHD and comorbid disorders
At the moment, there are no good treatments for obesity and substance use disorders, and there is little progress in the development of medication for ADHD in combination with depression. Within the CoCA project we are therefore investigating new treatment possibilities. In Frankfurt, Barcelona and London the first people with ADHD have received bright light therapy and physical exercise training to reduce symptoms of depression (the PROUD study). In Nijmegen this study will soon start as well. Meanwhile in Rostock (Germany), the circadian rhythm of participants with ADHD and other disorders is being measured. And in Frankfurt researchers are investigating the effects of dopamine agonists and antagonists on the reward system in the brain.
CoCA researchers in Norway have been searching the literature for new druggable targets for ADHD and comorbid disorders. A publication on many promising druggable genes can be expected soon. The first group of targets will be tested in an animal models.
Collaborations with patient organisations
Two representatives of ADHD patient organisations also joined our meeting: Andrea Bilbow from ADHD Europe, who is a partner in the CoCA project, and Ken Kilbride from ADHD Ireland. It was good to have these experts with us, and discuss with them how we can best translate our research findings to the people who should benefit from these findings. In Ireland for instance, there is very little knowledge about adult ADHD amongst health care professionals. It is therefore essential that our knowledge is also transferred to them, so that they can provide better care.
With the help of Andrea and Ken, we came up with a lot of new ideas for ADHD Awareness Month. During the entire month of October we aim to generate more awareness about. We will specifically target schools, such as universities and German Berufschule to inform both pupils and teachers about how to recognise ADHD and comorbidities, in adolescence and adulthood.
With the project being almost half way, we feel that we’re progressing very well (and our external advisor Jim Swanson – who attend the meeting as well – agrees!). In the coming year, we expect many exciting publications to appear and we will organise several symposia on international scientific conferences to share with you what we’ve found. By collaborating with patient organisations across Europe we will also share our knowledge with patients, family members, health care professionals and teachers. You can follow all of our progress on this blog!
This blog was written by Jeanette Mostert. Jeanette is dissemination manager of the CoCA project.
1: Solberg, Halmøy, Engeland, Igland, HAavik & Kungsøyr (2018) Gender differences in psychiatric comorbidity: a population‐based study of 40 000 adults with attention deficit hyperactivity disorder. Acat Psychiatria Scandinavia, 137 (3): 176 – 186. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5838558/
2: Chen, Kuja-Halkola, Sjölander, Serlachius, Cortese, Farone, Almgvist & Larsson (2017) Shared familial risk factors between attention-deficit/hyperactivity disorder and overweight/obesity – a population-based familial coaggregation study in Sweden. Journal of child psychology and psychiatry, 58 (6): 711-718. https://www.ncbi.nlm.nih.gov/pubmed/28121008
3: Du Rietz, Coleman, Glanville, Wan Choi, O’Reilly & Kuntsi (2018) Association of Polygenic Risk for AttentionDeficit/Hyperactivity Disorder With Co-occurring Traits and Disorders. Biological Psychiary CNNI, in press. https://www.sciencedirect.com/science/article/pii/S2451902217302318?via%3Dihub