On a coalmine and an MRI scanner – Is it fun, participating in DELTA?

About two and a half years ago, Dr. Emma Sprooten started the DELTA project. In DELTA, acronym for Determinants of Long-term Trajectories in ADHD, she investigates factors that contribute to the difference in (severity of) symptoms and impairment in people who were diagnosed with ADHD as a child. Previously, these adults participated in a study called NeuroImage when they were a child. We asked them if they were willing to participate one more time in this study. In the coming three weeks, we will post three blogs about the project. This is blog 1.

2019. Somewhere in autumn. Trees have become all shades of brown, yellow and red. We pass forests while driving on a German highway, all the way from Holland. After a while, the landscape changes from the colored forest to an industrial town. It is grey and gloomy, packed with old-fashioned industry buildings. Soon, the navigation sends us into an even more surreal place. We find ourselves surrounded by rusty brown pipes in a place that feels like an abandoned factory. If we would not know better, we would begin to feel a bit worried about what could happen here… 

What brings us here in this desolate area? To put it short, a bunch of people who were diagnosed with ADHD during their childhood, and a hypermodern 7 Tesla MRI scanner. Over ten years ago, as children, our participants first came in together with their parents and siblings. They played games, were interviewed and got an MRI scan, that was presented to them as ‘ a picture of the inside of your brain’. Now, we are repeating these measurements for a third time, with an upgrade from 3 Tesla to 7 Tesla MRI, allowing even more detailed pictures of their brains.

For scientists it is extremely valuable that people are willing to take part in this research. This is one of the few cohorts in the world in which people with ADHD are followed up for such a long time. It makes it possible to investigate which factors influence the different clinical trajectories that ADHD can take:. We are now testing people for already a third time in the NeuroImage project, that started in 2009. The current follow-up is called the DELTA project. More on the content of the project in our third blog. 

Next week, we’ll give you a peek into what a participant experiences during a test day in Essen. 

If you cannot wait to get some information on NeuroImage, see: https://www.ru.nl/donders/vm-site/collaborations/projects/neuroimage/

For a peak into Zollverein, the world heritage site where the 7 Tesla scanner is located, see: https://www.zollverein.de/zollverein-unesco-world-heritage-site/ The photo at the top of this post shows a detail of the coal mine at Zollverein.

From genes to driving schools: an Estonian program to reduce traffic accidents

Image by Netto Figueiredo from Pixabay

Driving is dangerous. 1.35 million people die from road accidents every year, according to the World Health Organization [1]. Young people who just obtained their driving license, and especially young men,  are at the highest risk for accidents. They are often seeking sensation, are more likely to take risks, and are more prone to take impulsive or thoughtless decisions while driving. To target this specific group, Estonian researchers have developed a training program for driving schools to make people aware of their impulsive tendencies.

Genetic predictors of traffic accidents

Interestingly, this Estonian research group that is led by professor Jaanus Harro specializes in genetics. Next to studying rats, Harro wanted to also investigate impulsive and aggressive behavior in humans. To measure this objectively outside of a laboratory setting they used data on traffic offences and accidents. Harro and his group found that a particular variation in the gene called 5-HTTLPR was associated with the number of speeding offences and traffic accidents [2]. People who have the short version of this variant are less likely to be caught for speeding or be involved in accidents, compared to those with the long variant.

The gene 5-HTTLPR is an important player in the serotonin system in the brain. Serotonin is a messenger molecule with many functions, one of them being the regulation of mood, impulsivity and aggression. Some people are more prone to act without thinking, or without considering the consequences, and this can partly be explained by genetics.

Reducing impulsive driving behavior

So should only people with the short version of 5-HTTLPR be allowed to drive? No, Harro and his team came up with something better: a program to reduce impulsive behavior on the road. They gave this to students who were learning to drive. In the training, students discussed their own impulsive tendencies, and ways to overcome these tendencies. There was also a control group that did not receive this extra lesson. Four years after obtaining their licenses, the group that received the training had been less involved in traffic violations and accidents than the control group. What’s more, those individuals with the long variant of 5-HTTLPR – so the ones who are more likely to be impulsive, based on this gene – benefited from the training the most.

For the driving schools the main implication of this experiment is that it is very beneficial to incorporate awareness training about impulsivity into driving lessons. Already eight driving schools in Estonia are providing the program to their students. The genetic findings however are mainly of interest to the researchers, who are hoping to gain a better understanding of impulsive and aggressive behavior. In addition to the serotonin-gene, they have found that genetic variations in the noradrenaline and dopamine system are also linked to traffic offenses and speeding, and to the effectiveness of the training [3, 4]. And just recently, they found that the neuropeptide orexin is linked to both aggression and to the prevalence of drunk driving and traffic accidents [5].

Beyond genetics

In addition to genes, other factors such as age, intelligence, and stressful life events influence the risk of offences and accidents as well, but we still know very little about how this works. That is why Harro and his team are now investigating the interactions between genes and environment. This research is part of the horizon2020 projects CoCA and Eat2beNICE. Ultimately, through a better understanding of our biology they hope to improve the way that people behave on the road, thereby reducing the number of accidents.

Meanwhile, Jaanus Harro travels to ministries and other governmental organizations in Estonia and Finland, to convince them to implement the training program on a national level, and to provide funds for further research. And in case you wonder about Harro’s own driving habits: although he acknowledges that he is quite impulsive, he assures us that he has learned to keep this under control while driving.

Jaanus Harro was recently interviewed by Science Business about this topic. Parts of this blogpost ar based on this interview. You can read the article here: https://sciencebusiness.net/keeping-drivers-impulses-check

References

[1] https://www.who.int/news-room/fact-sheets/detail/road-traffic-injuries (accessed 3 January 2020).

[2] Eensoo, Paaver, Vaht, Loit & Harro (2018). Risky driving and the persistent effect of a randomized intervention focusing on impulsivity: The role of the serotonin transporter promoter polymorphism. Accident Analysis and Prevention, 113, 19-24. https://www.ncbi.nlm.nih.gov/pubmed/29407665

[3] Paaver, Eenso, Kaasik, Vaht, Mäestu & Harro (2013). Preventing risky driving: A novel and efficient brief intervention focusing on acknowledgement of personal risk factors. Accident Analysis and Prevention, 50, 430-437. https://www.ncbi.nlm.nih.gov/pubmed/22694918

[4] Luht, Tokko, Eensoo, Vaht & Harro (2019). Efficacy of intervention at traffic schools reducing impulsive action, and association with candidate gene variants. Acta Neuropsychiatrica, 31, 159 – 166. https://www.ncbi.nlm.nih.gov/pubmed/31182183

[5] Harro, Laas, Eensoo, Kurrikoff, Sakala, Vaht, Parik, Maëstu & Veidebaum (2019). Orexin/hypocretin receptor gene (HCRTR1) variation is associated with aggressive behaviour. Neuropharmacology, 156. https://www.ncbi.nlm.nih.gov/pubmed/30742846

 

Mythbusters: artificial food colours and ADHD

When I was a kid, there was a boy in my class called Jeroen. At times I found him friendly and funny, but other times he would drive me insane with his hyperactive behaviour, jumping around and pulling my hair. Then one day, he told us that we wasn’t aloud to eat anything with artificial food colours anymore. This was supposed to reduce his hyperactivity. I was hopeful, but also sceptical if this would work.

Now that I’m involved in an international consortium investigating food and behaviour, I finally had the chance to learn about food colours and ADHD. Turns out, there is some truth to the claim, although it may only be true for some children, and it may not be specific to ADHD.

A shitty story

To better understand the effects of food on behaviour, we need to start at the end. Your poo can actually tell us a lot about the billions of microbes that live in your gut and help to digest the food you eat. For a long time, we didn’t know much about this micro-wildlife, until scientists developed techniques to analyse large amounts of DNA very quickly and cheaply. As every species has unique DNA, researchers can identify all the different species that live in your gut by analysing their DNA from poo. This helps us to better understand the many important roles that the gut bacteria play in your body, including your brain. For instance, certain bacteria produce neurotransmitters from digesting fibres. These neurotransmitters are important for the communication between brain cells.

ADHD

What does this have to do with ADHD? ADHD is a neurodevelopmental condition, which means that the brain develops differently compared to typically developing children. This influences the functioning of the brain and hence people with ADHD have problems focussing their attention, controlling their impulses and regulating their activity. A disruption in the neurotransmitter system is thought to play a key role in this. While the main cause of ADHD is genetic, environmental factors are also known to increase the risk of the condition, such as smoking during pregnancy, toxins in the environment, and food allergies. Since recently, researchers are investigating the gut bacteria (aka the poo) to better understand how food allergies may trigger ADHD [1].

Food allergies

The microbes in the gut interact closely with the immune system. During development the immune system has to learn that many foreign substances in the intestines (i.e. food and bacteria) are good and should not be attacked. In a way, it has to learn not to overreact. And this is what happens with food allergies. The over-reaction of the immune system is harmful for both the gut environment and for the brain, especially if it happens very often. Hence, an allergic reaction to food colourings may trigger small changes in the brain that in turn may trigger behaviour such as hyperactivity. How this works exactly is still unknown.

Based on this theory, clinicians and nutritionists are now investigating if special diets can reduce ADHD symptoms [2]. In such a diet, a child is put on a very restrictive diet that eliminates any potentially allergenic substances. To see which food types trigger the symptoms, specific foods are introduced one by one. For some children, this really seems to work well and they can manage their symptoms by not eating certain foods the rest of their lives. The elegance of this method is that it is based on the individual. While one person may need to eliminate food colourings, for another it could be certain fruits, or cow’s milk.

Myth busted?

Do artificial food colours cause ADHD? This may be the case for some children. In others, other types of food may trigger ADHD symptoms. And in yet another group of children, their ADHD has nothing to do with food allergies. At the moment, the only way to find out is through trial and error. But only try this under supervision of trained nutritionists and clinicians!

Back to Jeroen. I don’t remember him getting less annoying. Perhaps he was not allergic to food colourings at all, and he should have tried the complete elimination diet or different medication. Or perhaps I was just an eight-year old girl allergic to all boys.

References

  1. Dam, S. et al. (2019) The Role of the Gut-Brain Axis in Attention-Deficit/Hyperactivity Disorder. Gastroenterol Clin N Am, 48, 407–431
  2. Ly, V. et al. (2017) Elimination diets’ efficacy and mechanisms in attention deficit hyperactivity disorder and autism spectrum disorder. European Child and Adolescent Psychiatry, 26, 1067-1079.

This blog was written by dr. Jeanette Mostert. She is a neuroscientist and science communicator. She is involved in the CoCA-project and Eat2beNICE project. In the latter she is learning all about the links between food and mental health. 

Food & mental health: the Eat2beNICE project

We all know that a healthy lifestyle is beneficial for our health. But many of us forget that eating healthy, exercising regularly and getting enough sleep is also important for good mental health. In the Eat2beNICE research project a large team of researchers is investigating the link between food and mental health, specifically impulsivity, compulsivity and aggression. To share this knowledge with the rest of the world, they work together with food consultant Sebastian Lege.

The Eat2beNICE project just released a video to explain what the research is about and why it’s important. In this video Sebastian Lege visits the project coordinator Alejandro Arias-Vasquez, en several other researchers in the consortium.

More information about the Eat2beNICE project can be found at http://www.newbrainnutrition.com

 

 

 

 

 

IMpACTnextgen: the next generation of IMpACT researchers

orebroimpactnextgen

Near the beautiful castle in Örebro, Sweden 2018, we kicked off our new network of enthusiastic researchers working in the ADHD research field. This network consists of early and mid-career researchers who work on topics related to ADHD across the lifespan and have a link with one of the IMpACT (International Multicenter persistent ADHD CollaboraTion) projects.

Our network has the aim to unite the knowledge of the individual young researchers in the field of ADHD to boost the further development of our field. Furthermore, we aim to facilitate the exchange of students and offer them international experiences in our research labs. Our final aim is to have closer ties between the members. This way it will become easier to replicate research findings, collaborate and brainstorm with researchers that work on related topics.

In Frankfurt 2019 we decided to start working towards a first collaborative project. More about this will follow soon.

Our work can be followed here on ‘mind-the-gap.live’ by our tag ‘impactnextgen’

 

impactnextgen2019

If you want to join or have ideas, please contact any of us, or contact Martine Hoogman martine.hoogman@radboudumc.nl (chair)

 

Busting ADHD myths

This year’s ADHD Awareness Month was themed “ADHD myths and facts, know the difference”. As scientists, we feel that it is our role to spread the facts about ADHD. But what myths are there about ADHD? To get a better idea of this, we chose to interview people and just ask them what they know about ADHD. What are the symptoms? How do you get ADHD? Can adults have ADHD?

The people that we interviewed actually were quite well informed about ADHD. Most know that people with ADHD have problems with controlling their attention, with sitting still and that they often have a lot of energy.  And about half the people that we interviewed suspect that also adults can have ADHD. But we also noticed some myths.

Myth 1: People with ADHD are always active and have a lot of energy

ADHD is not just characterised by hyperactivity and restlessness. Many people with ADHD are actually quite capable of sitting still, but suffer more from a kind of inner restlessness and mindwandering. Also problems with focussing attention are very typical for ADHD, and there are people who only have this inattentive ADHD subtype, without the hyperactivity. What many people also don’t know is that people with ADHD often suffer from emotional dysregulation such as regalting your emotions and easily getting irritable or angry.

Myth 2: Only children can have ADHD

Although ADHD is wellknown in children, adults can also have ADHD. It is estimated that around 15% of the children with ADHD will continue to have the full diagnosis in adulthood. But about 60 – 80% of children with ADHD will still have symptoms of ADHD when they are adults. Often, the hyperactivity symptoms of ADHD reduce when children get older, but the inattention symptoms often remain.

These videos were created with help of early career scientists of the CoCA project (www.CoCAproject.eu)

 

Do you want to learn more about ADHD myths and facts? Have a look here:https://adhdawarenessmonth.org/myths-and-facts-about-adhd/

And keep watching this site, because more mythbusting videos will be coming!

Do you have an ADHD myth that you want to have busted? Or are you unsure about whether something is a myth or fact? Let us know in the comments and we’ll answer you!

 

How reliable is a diagnosis of ADHD in adults?

ADHD is classified as a neurodevelopmental disorder. This implies that ADHD starts during childhood and may, or may not, last into adulthood. According to this definition, a diagnosis of ADHD in adults requires two separate criteria to be satisfied: (i) Present diagnostic criteria must be fulfilled and (ii) ADHD symptoms must have started during childhood (before 7 years of age in DSM-IV and 12 years in DSM-5).

It’s relatively easy to evaluate present symptoms and differential diagnoses and to make a clinical decision. However, the second requirement has generated much headache and frustration. Is it really possible to evaluate childhood symptoms in a typical 40 year old patient, decades after the person left school and with limited documentation from family and peers?

Some argue that the criteria of childhood symptoms of ADHD are not satisfied unless there is a well-documented record of child developmental problems. Others put more faith in personal (subjective) recollection of childhood memories. These diverging views have culminated in an intense and heated debate about the possible existence of adult-onset ADHD and whether age-of-onset criteria are meaningful in clinical management of ADHD (1).

We all know from experience that memories tend to fade. Memories cannot be trusted. Research has shown that memories can be systematically biased and manipulated in many ways. Experimental psychology has provided a long list of well documented examples of memory bias, including mood congruent memory bias, consistency bias, positivity effect when older people favor positive over negative information in their memories, suggestibility bias when ideas suggested by the clinician are mistaken for true memories etc. (2). All of these effects and many more are well documented in forensic psychology and popular press and are experienced in routine clinical practise.

Despite of the obvious limitations of retrospective recollection of childhood experiences, a diagnosis of ADHD in adults is routinely based on retrospective reports of childhood experiences, often in the form of semi-structured interviews or rating scales. The Wender Utah Rating Scale (WURS) is the most widely used retrospective rating scale of childhood ADHD symptoms (3). The 25-item version of WURS has acceptable psychometrical properties, but its long-term stability is not known and it is also unclear how WURS scores are affected by other concurrent symptoms and conditions.

To investigate these factors, Lundervold and coworkers recently examined the test–retest reliability of the WURS in 85 adults with ADHD and 189 controls. They found that WURS scores were relatively stable over a time-span of seven years, but also that the scores were strongly influenced by present ADHD symptom severity, as well as other concurrent psychiatric disorders (4).

Based on these observations, the authors conclude that the WURS may be valuable in diagnostic assessments of ADHD, but that clinicians need to be cautious in the interpretation of the results. We all need to be aware of the many factors that can distort recollection of childhood memories. This study also demonstrates how difficult it is to strictly apply the age of onset criteria in adult psychiatric clinical settings.

References

  1. Franke B, Michelini G, Asherson P, Banaschewski T, Bilbow A, Buitelaar JK, Cormand B, Faraone SV, Ginsberg Y, Haavik J, Kuntsi J, Larsson H, Lesch KP, Ramos-Quiroga JA, Réthelyi JM, Ribases M, Reif A.Live fast, die young? A review on the developmental trajectories of ADHD across the lifespan. Eur. Neuropsychopharmacol. 2018 Oct;28(10):1059-1088.
  2. Schacter DL, Dodson CS. Misattribution, false recognition and the sins of memory. Philos Trans R Soc Lond B Biol Sci. 2001 Sep 29;356(1413):1385-93.
  3. Stein MA, Sandoval R, Szumowski E, Roizen N, Reinecke MA, Blondis TA, et al. Psychometric characteristics of the Wender Utah Rating Scale (WURS): reliability and factor structure for men and women. Psychopharmacol Bull 1995;31:425–33.
  4. Lundervold AJ, Vartiainen H, Jensen D, Haavik J. Test-Retest Reliability of the 25-item version of Wender Utah Rating Scale. Impact of Current ADHD Severity on Retrospectively Assessed Childhood Symptoms. J Atten Disord. 2019 Oct 4:1087054719879501.

It’s ADHD Awareness Month – know the facts and bust the myths!

It’s October, and that means that it’s ADHD Awareness Month again. Throughout this month people all across the globe will be raising awareness about Attention Deficit Hyperactivity Disorder (ADHD). As ADHD researchers, we of course contribute to this by sharing with you what we know – and what we yet don’t know – about ADHD.

To start off, let’s re-watch the beautiful mini-documentary that was created last year: Shine a light – understanding ADHD. In this video we see several people with ADHD as well as ADHD researchers, who all explain how they see, experience and investigate ADHD.

This year’s ADHD Awareness Month is about myths and facts. On this website you can find some very nice articles that clearly explain the facts: for instance why ADHD is not an excuse for laziness, and why about half of the children with ADHD do not grow out of it when they reach adolescence and adulthood. For this last reason, many of us are studying ADHD in adulthood. For instance in the IMpACT research consortium.

In a few weeks we will be releasing a series of videos in which some more myths about ADHD are being debunked. These videos are being created by researchers from the CoCA-consortium. The research done in this consortium is aimed to stop the spiral from ADHD into depression and obesity, as was written in this nice article by the European Commission.

Another intersting new research theme is whether lifestyle choices such as diet and exercise can influence how we behave and feel. If you want to learn more about this, I refer you the website New Brain Nutrition, which has several very interesting learning modules, as well as a nice blog.

We hope that through these websites we inspire you to learn more about ADHD. Know the facts, and bust the myths!

 

More information:

http://www.adhdeurope.eu

http://www.adhdawarenessmonth.org

http://www.coca-project.eu

http://www.newbrainnutrition.com

http://www.impactadhdgenomics.com

https://ec.europa.eu/research/infocentre/article_en.cfm?artid=50905

 

“No I do not have ADHD, I am just busy!”, but still very interesting for genetic studies!

Do you sometimes find it difficult to pay attention? Can you be very disorganized at times, or very rigid and inflexible? Although difficulties with attention, organization and rigidity are symptoms of psychiatric disorders, these traits are not unique to people with a diagnosis. And that is very useful for studying the genetics of psychiatric disorders.

Being easily distracted, liking things to go in a certain way, having a certain order in the way you do things, these might all be things you recognize yourself (or someone you know) in, while you (or they) are not diagnosed with any psychiatric disorder. We actually know that many of these symptoms are indeed found in a range in the general population, with some people showing them a lot, some a little and some not at all. If these symptoms are also present in people without a diagnosis then why should we only study people with a diagnosis to learn more about the biology of symptom-based disorders?

Many psychiatric disorders, like attention-deficit/hyperactivity disorder (ADHD) and autism spectrum disorder (ASD) are disorders that ‘run in the family’. Using family-based and genetic studies it was found that they are actually highly heritable. However the underlying genetic risk factors turned out to be difficult to find. Enormous samples sizes (comparing more than 20 000 people with the disorder to even more individuals without the disorder) were needed to robustly find just a few genetic risk factors, although we know that many more genetic factors contribute. Even though these disorders are highly prevalent, collecting genetic data on psychiatric patients for research is still challenging. Using population-based samples – that include all varieties of people from the general population – can be a good alternative to reach large sample sizes for powerful genetic studies.

Taking together the fact that psychiatric-like symptoms are also, to a certain degree, present in the general population, and the fact that genetic studies can benefit from large(r) sample sizes to find genetic associations, it can be very interesting to study psychiatric-like traits in population-based samples. This is indeed what happened in the field of psychiatric genetics. The first proof-of-concept studies were able to show an astonishing overlap in genetic factors of more than 90% between ADHD and ADHD symptoms in the general population. Our own research group was able to show that certain autistic traits, like rigidity, indeed share a genetic overlap with ASD and that genes that were previously linked to ASD show an association to autistic traits in the population. These results show that genetic factors involved in disorder-like traits are overlapping with genetic factors involved in the clinical diagnosis, and therefore can indeed be used to study the biology of psychiatric disorders.

So next time you feel distracted/rigid/disorganized, don’t get discouraged, but consider signing up for a genetic study. Science might need you!

Janita Bralten is a postdoctoral researcher at the department of Human Genetics in the Radboud university medical center, Nijmegen, the Netherlands. Her research focusses on the genetics of psychiatric disorders.

Further reading:

Bralten J, van Hulzen KJ, Martens MB, Galesloot TE, Arias Vasquez A, Kiemeney LA, Buitelaar JK, Muntjewerff JW, Franke B, Poelmans G. Autism spectrum disorders and autistic traits share genetics and biology. Mol Psychiatry. 2018 May;23(5):1205-1212.

Middeldorp CM, Hammerschlag AR, Ouwens KG, Groen-Blokhuis MM, Pourcain BS, Greven CU, Pappa I, Tiesler CMT, Ang W, Nolte IM, Vilor-Tejedor N, Bacelis J, Ebejer JL, Zhao H, Davies GE, Ehli EA, Evans DM, Fedko IO, Guxens M, Hottenga JJ, Hudziak JJ, Jugessur A, Kemp JP, Krapohl E, Martin NG, Murcia M, Myhre R, Ormel J, Ring SM, Standl M, Stergiakouli E, Stoltenberg C, Thiering E, Timpson NJ, Trzaskowski M, van der Most PJ, Wang C; EArly Genetics and Lifecourse Epidemiology (EAGLE) Consortium; Psychiatric Genomics Consortium ADHD Working Group, Nyholt DR, Medland SE, Neale B, Jacobsson B, Sunyer J, Hartman CA, Whitehouse AJO, Pennell CE, Heinrich J, Plomin R, Smith GD, Tiemeier H, Posthuma D, Boomsma DI. A Genome-Wide Association Meta-Analysis of Attention-Deficit/Hyperactivity Disorder Symptoms in Population-Based Pediatric Cohorts. J Am Acad Child Adolesc Psychiatry. 2016 Oct;55(10):896-905.

If you are interested in joining a scientific study see for example:

https://www.ru.nl/donders/vm-site/proefpersonen/engelse-versies-centers/participants/donders-centre-cognition-en/

or

https://www.impactadhdgenomics.com/patienten/nl/deelnemen (Dutch only)

Cocaine dependence is in part genetic, and it shares genetic risk factors with other psychiatric conditions and personality traits.

Cocaine is one of the most used illicit drugs worldwide and its abuse produces serious health problems. In Europe, around 5.2% of adults (from 15 to 64 years old) have tried cocaine, but only 20% will develop addiction. Why? Genetics is part of the answer. Cocaine dependence is a complex psychiatric disorder that results from the interaction of both environmental and genetic risk factors. Twin and adoption studies indicate that genetic alterations contribute substantially to cocaine dependence susceptibility, which has an estimated genetic load (heritability) as high as 65-79%. Although many studies with focus on candidate genes have been performed, only a few risk variants for cocaine dependence have been identified and replicated so far.

https://www.
flickr.com/photos/30478819@N08/24042216187

In this study we performed a meta-analysis of genome-wide association studies (GWAS) of cocaine dependence using more than 6,000 European ancestry individuals. This approach allowed us to inspect a huge number of genetic variants distributed all along the genome that are common in the general population. We identified a gene (HIST1H2BD) associated with cocaine dependence that is located in a region on chromosome 6 enriched in genes that encode histones, proteins that combine with DNA, protecting it and contributing to the activation (or inhibition) of genes. Some of these genes have previously been associated with schizophrenia.

Several studies have shown that substance use disorders (SUD), and especially cocaine dependence, co-occur in patients with other psychiatric disorders and personality traits. Such comorbidity is associated with increased severity for all disorders, although it is unclear whether this relationship is causal or the result of shared genetic and/or environmental risk factors. We calculated the shared genetics (genetic correlation) between cocaine dependence and six comorbid conditions. For the first time we found significant genetic correlation with attention deficit/hyperactivity disorder (ADHD), schizophrenia, major depression and risk- taking behavior. We also used another approach (polygenic risk score analysis, PRS) to prove that all tested comorbid conditions are associated with cocaine dependence status, suggesting that cocaine dependence is more likely in individuals that carry genetic risk factors for the tested conditions than in those that do not.

To our knowledge, this is the largest reported GWAS meta-analysis in European-ancestry individuals with cocaine dependence. We identified suggestive risk factors for the disorder in several genomic regions and found evidence for shared genetic risk factors between cocaine dependence and several co-occurring psychiatric traits. However, the size of the sample is still limited and further studies are needed to confirm our results.

Read more at: https://www.sciencedirect.com/science/article/pii/S0278584619301101?via%3Dihub

Judit Cabana-Domínguez and Bru Cormand

Judit Cabana Domínguez is a Postdoctoral researcher at the Genetics, Microbiology and Statistics Department at the University of Barcelona.

Bru Cormand is Full Professor of Genetics at the Genetics, Microbiology and Statistics Department at the University of Barcelona.