These are the world’s most high ranking experts on ADHD

Who are the most knowledgeable people about ADHD in the world? According to the website, these are professors Stephen Faraone (SUNY upstate University), Samuel Cortese (University of Southampton) and Jan Buitelaar (Radboud University Nijmegen).

What’s more, several scientists who are involved in our research consortia that investigate ADHD (i.e. Aggressotype, CoCA, IMpACT, Eat2beNICE) are top-ranked in this list of more than 30.000 possible experts in the field. These include Stephen Faraone, Jan Buitelaar, Philip Asherson, Barbara Franke, Joseph Antoni Ramos-Quiroga, Henrik Larsson, Catharina Hartman and Pieter Hoekstra. What this means is that the ADHD research that we do, and that is often reported on in this blog, is lead by the world’s top ADHD experts.

‘Our’ top-ranked ADHD experts. From left-to-right: Stephen Faraone, Jan Buitelaar, Philip Asheron, Barbara Franke, Joseph Antoni Ramos-Quiroga, Henrik Larsson, Catharina Hartman, Pieter Hoekstra.

How is an expert defined?

The website expertscape was started by John Sotos when he was looking for an expert on Parkinson’s disease to treat his uncle. This turned out to be more difficult than he thought. As John Sotos was a doctor himself, he luckily had a large network of doctors that he could contact about this. But this made him realise that people who don’t have such a network, would not be able to find out who the most knowledgeable persons are on a particular topic. He therefore created this website

The way the website works is quite simple: it searches for academic, peer-reviewed publications by a certain person on a certain topic. The more someone has published on a topic, the higher this person is ranked. Thus,  “[a]n expert is not just someone who knows a lot about a particular topic. We additionally require that the expert write about the topic, and be involved at the leading edge of investigation of the topic.”

This means that the site is actually not a very good tool to find a good doctor. As the website acknowledges “a great doctor has many important qualities beyond expert knowledge of your very specific medical condition.” However, it does mean that the website is pretty good at providing a simple overview of who has a lot of scientific knowledge about a specific topic.

So are they really experts?

In the past years I have met with most people in the top of this list, and I dare say that they are very knowledgeable indeed. Each of them has been working in the ADHD field for a considerable amount of time and has added important new insights into ADHD through research and publications. What I find most striking from this list however, is that most of these experts work together in consortia and international networks. And that is how the field really moves forward: by combining the knowledge of all these experts.

Several of these experts have also written for this blog:




This blog was written by Jeanette Mostert. Jeanette studied brain connectivity in adult ADHD during her PhD. She is now dissemination manager of the international consortia CoCA and Eat2beNICE. 


Epigenetic signature for attention-deficit/hyperactivity disorder

Attention-deficit/hyperactivity disorder (ADHD) is considered a complex disorder caused by underlying genetic and environmental risk factors. To make it even more complex, environmental factors can influence the expression of genes. This is called epigenetics.

Given the large proportion of the heritability of ADHD still to be explained, there is a growing interest in the epigenetic mechanisms that modulate gene expression. microRNAs (miRNA) are small parts in the human genome that do not code for genes, but instead regulate the expression of other genes by promoting the degradation or suppressing the translation of those target genes. miRNA therefore provide a means to integrate effects of genetic and environmental risk factors.

The human genome encodes more than 2500 different miRNAs, the majority of which are expressed in the brain. miRNAs are known to be involved in the development of the central nervous system and in many neurological processes including synaptic plasticity and synaptogenesis. Given the limited accessibility of the human brain for studying epigenetic modifications, miRNA profiling in peripheral blood cells is often used as a non-invasive proxy to study transcriptional and epigenetic biosignatures, and to identify potential clinical biomarkers for psychiatric disorders.

We recently investigated the role of microRNAs in ADHD at a molecular level, by conducting the first genome-wide integrative study of microRNA and gene expression profiles in blood of individuals with ADHD and healthy controls. We identified three miRNAs (miR-26b-5p, miR-185-5p and miR-191-5p) that have different expression levels in people with ADHD, compared to those without ADHD. When we investigated downstream miRNA-mediated mechanisms underlying the disorder this provided evidence that aberrant expression profile of these three miRNA may underlie changes in the expression of genes related with myo-inositol signaling. This mediates the biological response of a large number of hormones and neurotransmitters on target cells. We also found that these miRNAs specifically targeted genes involved in neurological disease and psychological disorders.

These findings show that epigenetic modifications through microRNAs play a role in ADHD, and provide novel insights into how these miRNA-mediated mechanisms contribute to the disorder. In the future, these miRNAs may be used as peripheral biomarkers that can be easily detected from blood, as is shown in the figure.

What´s next?

The mechanism through which miRNAs modify gene expression is complex and dynamic. Therefore, future studies are required to provide deeper insights into the epigenetic mechanisms underlying ADHD, and to identify specific molecular networks that may be crucial in the development of the disorder.

Further reading

Cristina Sánchez-Mora et al. Epigenetic signature for attention-deficit/hyperactivity disorder: identification of miR-26b-5p, miR-185-5p, and miR-191-5p as potential biomarkers in peripheral blood mononuclear cells, Neuropsychopharmacology, volume 44, pages 890–897 (2019).

About the author

Cristina Sánchez-Mora is postdoctoral researcher at the Psychiatry, Mental Health and Addictions group at Vall d’Hebron Institut de Recerca (VHIR). Her research is part of the CoCA consortium that investigates comorbid conditions of ADHD

ADHD and cannabis use

It is not uncommon for individuals to suffer from two or more psychiatric disorders at the same time. The appearance of these disorders frequently follows a specific order, and one disorder may predispose to others, all of which in combination contribute to the worsening of the quality of life of the individuals who suffer them. This is usually associated with more severe symptoms and worse prognosis. In addition, making a diagnosis and applying personalized treatments becomes more challenging in this context. By investigating the genetic overlap between disorders, we gain better understanding of why the disorders frequently co-occur.

In mental health, substance use disorders often appear when there is another mental condition. This is the case for attention-deficit/hyperactivity disorder (ADHD) and substance use disorder, where individuals with ADHD are more likely to use drugs during their lifetime than individuals who do not have ADHD. In particular, cannabis is the most commonly used substance among individuals with ADHD, which can also lead to the use of other drugs and to the worsening of their symptoms. ADHD is one of the most common neurodevelopmental disorders, affecting around 5% of children and 2.5% of adults, and is characterized by attention deficit, hyperactivity and impulsivity. Both ADHD and cannabis use are conditions determined partly by environmental factors but where genetic factors also play an important role.

We recently investigated the genetic overlap between ADHD and cannabis use, and found that the increased probability of using cannabis in individuals with ADHD, can be, in part, due to a common genetic background between the two conditions. We identified four genetic regions involved in increasing the risk of both ADHD and cannabis use, which could point to potential druggable targets and help to develop new treatments. In addition, we confirmed a causal link between ADHD and cannabis use, and estimated that individuals with ADHD are almost 8 times more likely to consume cannabis than those who do not have ADHD. This evidence goes in line with a temporal relationship, where the ADHD appears in childhood and the use of cannabis during adolescent or adulthood. This suggests that having ADHD increases the risk of using cannabis, and not vice versa.

This research has only been possible thanks to large international collaborations by the Psychiatric Genomics Consortium (PGC), iPSYCH, and the International Cannabis Consortium (ICC), where the genomes of around 85 000 individuals were analysed.

Overall, these results support the idea that psychiatric disorders are not independent, but have a common genetic background, and share biological pathways, which put some individuals at higher risk than others. This will help to overcome the stigma of addiction and mental disorders. In addition, the potential of using genetic information to identify individuals at higher risk will have a strong impact on prevention, early detection and treatment.

Further reading

María Soler Artigas et al. Attention-deficit/hyperactivity disorder and lifetime cannabis use: genetic overlap and causality, Molecular Psychiatry (2019) –

About the author

María Soler Artigas is postdoctoral researcher at the Psychiatry, Mental Health and Addictions group at Vall d’Hebron Institut de Recerca (VHIR), also part of the Biomedical Research Networking Center in Mental Health (CIBERSAM). Her research is part of the CoCA consortium that investigates comorbid conditions of ADHD.