Aggression – Mind the Gap Blog

IS GENETICS BEHIND THE CO-OCCURRENCE OF ADHD AND OTHER DISORDERS?

Posted on May 10, 2021May 12, 2021 by Bru Cormand

A group of researchers from Spain, The Netherlands, Germany, Estonia, Denmark and USA have joined efforts to gain insight into the genetics of ADHD and its comorbidities. This ambitious objective was addressed by the Work Package 2 of a big project called CoCA: “Comorbid Conditions of Attention deficit/hyperactivity disorder (ADHD)”, funded by the European Union for the period 2016-2021.

In psychiatry, the co-occurrence of different conditions in the same individual (or comorbidity) is the rule rather than the exception. This is particularly true for ADHD, where conditions like major depressive disorder or substance use disorders frequently add to the primary diagnosis and lead to a worse trajectory across the lifespan.

There are different reasons that may explain the advent of the comorbidities: Sometimes the two conditions have independent origins but coincide in a single patient. Comorbidity can also appear as a consequence of a feature of a primary disorder that leads to a secondary disorder. For example, impulsivity, a trait that is common in ADHD, can be an entry point to substance use. Comorbidity can also be the result of shared genetic causes. The latter has been the focus of our investigations and it involves certain risk genes that act on different pathologies, a phenomenon called pleiotropy.

Our project started with an approach based on the exploration of candidate genes, particularly those involved in neurotransmission (i.e. the connectivity between neurons) and also in the regulation of the circadian rhythm. We used genetic data of more than 160,000 patients with any of eight psychiatric disorders, including ADHD, and identified a set of neurotransmission genes that are involved at the same time in ADHD and in autism spectrum disorder [1]. In another study we identified the same gene set as involved in obesity measures [2].

Then we opened our analyses to genome-wide approaches, i.e. to the interrogation of every single gene in the genome. To do that we used different statistical methods, including the estimation of the overall shared genetics between pairs of disorders (genetic correlation, r_g), the prediction of a condition based on the genetic risk factors for another condition (polygenic risk score analysis, PRS) and the establishment of the causal relationships between disorders (mendelian randomization). As a result, we encountered genetic connections between ADHD and several psychiatric disorders, like cannabis or cocaine use disorders [3, 4, 5], alcohol or smoking-related phenotypes [6, 7, 8], bipolar disorder [9], depression [6], disruptive behavior disorder [10], but also with personality or cognition traits, like neuroticism, risk taking, emotional lability, aggressive behavior or educational attainment [6 , 11, 12, 13], or with somatic conditions, such as obesity [11, 12].

All these results and others, reported in more than 40 (!) scientific publications, support our initial hypothesis that certain genetic factors cut across psychiatric disorders and explain, at least in part, the comorbidity that we observe between ADHD and many other conditions. This information can be very useful to anticipate possible clinical trajectories in ADHD patients, and hence prevent potential negative outcomes.

Dr. Bru Cormand is full professor of genetics and head of the department of Genetics, Microbiology & Statistics at the University of Barcelona. He leads workpackage 2 of the CoCA project (www.coca-project.eu) on the genetics of ADHD comorbidity.

References

Connection between sleep and mental health – a special case for ADHD

Posted on April 22, 2021April 22, 2021 by Dina Sarsembayeva

Bad sleep is… well, bad for you

Ever seen that meme with Homer Simpson lying awake in bed until 4 am and then falling asleep 8 minutes before the alarm rings? If it felt relatable, then you definitely know how relevant sleep problems can be! That situation shows problems with falling asleep (insomnia) as well as very late sleep timing (read more about this in my previous blog about circadian delay). Both are linked to an infinite number of health problems, especially mental illness. In fact, a typical teenager on TV can demonstrate how bad sleep affects you. Remember how moody, bad-tempered, inattentive at school they usually are or how much they drink and smoke? Well, bad sleep relates to very similar mental health problems: mood disorders, anxiety, aggression, attention deficit hyperactivity disorder (ADHD) and bad habits like smoking, drinking alcohol and taking drugs. The connection between bad sleep and ADHD, however, is one of the most studied.

What about sleep in people with ADHD?

We know that up to 80% of ADHD patients suffer from insomnia^1,2 and most of them have a circadian delay³. Researchers commonly find that if a person has insomnia symptoms and later bed times, then this person also suffers from more severe ADHD⁴. Although it’s not clear why exactly this happens, some think that a natural circadian delay doesn’t let you fall asleep at socially acceptable times, so you regularly get insufficient sleep^5,6. Interestingly, people without ADHD who sleep poorly also develop the same symptoms – inattention and hyperactivity⁷. You might even say that insomniacs develop temporary ADHD! This makes the connection between ADHD and sleep even more curious and important.

What did our research find?

My colleagues and I wanted to know if the same association with sleep happens in other mental illness and if it is different from the connection to ADHD. For this, we examined information from around 38,000 persons in The Netherlands with ages from 4 to 91. Each of them filled in a long online survey with questions about their sleep habits and mental health.

Later, we divided all these people into three groups based on their sleep behaviour. The first groups were people who prefer earlier sleep times and reported no insomnia symptoms. The other two groups comprised persons who preferred later sleep times (a sign of circadian delay). These groups differed in one thing: one group had very few symptoms of insomnia and the other a lot.

After that, we measured if some of these groups had more severe symptoms of mental illness, including ADHD. And yes, the groups with circadian delay – even the ones without insomnia – really did have significantly higher severity of all mental illness compared to early sleepers! Moreover, the individuals in the circadian delay group with insomnia had more mental health problems than those who slept well. In ADHD specifically, this link between circadian delay and insomnia was as large for symptoms of inattention as for hyperactivity/impulsivity. Children and adolescents had even stronger relation between poor sleep and mental health problems, just like that moody teenagers I mentioned before.

Why this matters

Insomnia and circadian delay, as we see from these results, is a common problem for different types of mental illness. Good sleep usually means better mental health, so people diagnosed with a mental illness might want to improve their sleep behaviour. The good news is that reducing mild insomnia might be easy: anyone can get blinders to keep their bedroom dark and drink less coffee. Circadian delay, though, is harder to change, because it is mainly ruled by your genes. This means that those born as late-night birds need to adapt their life to a more nocturnal rhythm to avoid worse mental state. Sadly, we all know it is often impossible. Younger people, for whom sleep is so important, still need to wake up unnaturally early for school. Adults go to sleep only late at night, even if they’d happily nap at 9 pm, because they were working all day and need to finish their house chores. Current expectations of a good worker and student fit morning people but fail to help and only cause more insomnia for those with a circadian delay. Unless we want to feed all adolescents melatonin tablets every day, our society needs to be more tolerant to our individual circadian preferences.

Dina Sarsembayeva is a neurologist and a research master’s student at the University of Groningen. She is using the data from the CoCa project to learn if the circadian preferences and sleep problems can be turned into profiles to predict specific psychiatric conditions.

1. Kessler, R. C. et al. Lifetime prevalence and age-of-onset distributions of mental disorders in the World Health Organization’ s. World Psychiatry 2007;6:168-176) 6, 168–176 (2007).

2. Lugo, J. et al. Sleep in adults with autism spectrum disorder and attention deficit/hyperactivity disorder: A systematic review and meta-analysis. Eur. Neuropsychopharmacol. 1–24 (2020) doi:10.1016/j.euroneuro.2020.07.004.

3. Coogan, A. N. & McGowan, N. M. A systematic review of circadian function, chronotype and chronotherapy in attention deficit hyperactivity disorder. Atten. Defic. Hyperact. Disord. 9, 129–147 (2017).

4. Lugo, J. et al. Sleep in adults with autism spectrum disorder and attention deficit/hyperactivity disorder: A systematic review and meta-analysis. Eur. Neuropsychopharmacol. 38, 1–24 (2020).

5. Çetin, F. H. et al. Chronotypes and trauma reactions in children with ADHD in home confinement of COVID-19: full mediation effect of sleep problems. Chronobiol. Int. 37, 1214–1222 (2020).

6. Eng, D. et al. Sleep problems mediate the relationship between chronotype and socioemotional problems during early development. Sleep Med. 64, S104 (2019).

7. Lunsford-Avery, J. R., Krystal, A. D. & Kollins, S. H. Sleep disturbances in adolescents with ADHD: A systematic review and framework for future research. Clin. Psychol. Rev. 50, 159–174 (2016).

What do rewards have to do with mental health problems?

Posted on September 28, 2020 by Dener Cardoso Melo

What do you think of when I say “rewards”? Perhaps you think of the points you collect every time you shop or the badges you get when playing a videogame. Well, then you’re right! A reward can be anything. A good grade, going on a trip with friends, a smile, and even that dessert you crave in the middle of the night. Rewards are any stimuli with the potential to make us seek and consume them, and if we like, we will probably want to get them again [1].

Actually, you crave that dessert because you ate it once, and you liked it so much that your brain learned that eating that dessert again will make you feel good. This happens because of a neurotransmitter called “dopamine” released when you eat the dessert, giving you that little rush of pleasure. Now your brain knows what you like and will want more of that.

By now, you probably have realized that rewards are present in virtually everything we do in our daily lives. That is why seeking and consuming rewards are considered to be a fundamental characteristic of human behavior. These rewards that we keep consuming guarantee that we stay alive by eating and drinking water, for example. Rewards also have a huge influence on how we experience positive emotions, motivate ourselves to perform tasks, and learn new things [2].

What about the relationship between rewards and mental health problems?

Although rewards are natural stimuli that make us keep doing healthy and nurturing things, it can also become a problem. Rewards are not the problem itself, but some people can have an unhealthy behavior towards rewards. That’s where mental health problems come in. Did you know that most mental health conditions have alterations in how rewards are processed in the brain? It’s so common that these so-called reward processing alterations are now considered a “transdiagnostic feature,” meaning we can find them across different mental health conditions [3].

Reward processing is a term to refer to all aspects related to how we approach and consume rewards. For instance, how you respond after getting a reward (responsiveness), how motivated you are to go after a reward (drive/motivation), how impulsive you are when trying to get new and intense rewards (fun-seeking/impulsivity). So, as you can see, it’s not only about getting the rewards, but many different things play a role in a simple action we do.

Let’s think of an example: You are going to a party with your best friends. You are motivated to go out with your friends because you’re always happy when you are around them [this is the drive/motivation]. Once you are at the party, you meet your friends, talk, laugh and are happy you decided to join because you’re feeling that rush of pleasure [this is the responsiveness aspect]. At some parties, things can get a bit out of control, and some people might do risky things on the spur of the moment, like binge drinking. You refuse to binge drink because you thought of the risks, and you don’t want to be in trouble later [that’s the third aspect, the fun-seeking/impulsivity].

Now, let’s think of how that party would be for people with reward processing alterations. In the case of a very high drive, they would be super motivated to hang out with friends. On the other hand, if they have low responsiveness, they wouldn’t be able to have fun at the party even though all of their friends are there and the party is super fun. Lastly, in the case of high fun-seeking/impulsivity, they wouldn’t think of the risks and consequences and engage in binge drinking anyways.

As I mentioned before, these alterations play a role in different mental health conditions. They can affect one or more aspects of reward processing, and they can be either lower or higher than average. For example, people with ADHD can show higher risk-taking, meaning that they are more susceptible to take big risks without thinking about the consequences [4]. This impulsive behavior might be a reflection of the altered fun-seeking aspect of reward processing. Another example is the lack of interest in social interactions in people with autism spectrum disorders [5]. This lack of interest might reflect a reduced drive/motivation to go after social rewards.

These are just some examples of what reward processing alterations might look like in the context of mental health problems. There are still a lot of open questions. As part of my PhD research, I am trying to answer some of them. For example, which came first? Are reward processing alterations causing mental health problems, or are they just mere symptoms of these conditions? If you want to learn more about this topic, stay tuned as more blog posts will come!

Dener Cardoso Melo is a PhD candidate at the University Medical Center Groningen (UMCG). He is using data from the CoCA project together with other datasets to investigate the potential causal role of reward processing alterations in different mental health conditions.

References

Schultz, W. (2015). Neuronal reward and decision signals: From theories to data. Physiological Reviews, 95(3), 853-951. doi:10.1152/physrev.00023.2014
Wise, R. A. (2002). Brain reward circuitry: Insights from unsensed incentives. United States: Elsevier Inc. doi:10.1016/S0896-6273(02)00965-0
Zald, D. H., & Treadway, M. T. (2017). Reward processing, neuroeconomics, and psychopathology. Annual Review of Clinical Psychology, 13(1), 471-495. doi:10.1146/annurev-clinpsy-032816-044957
Luman, M., Tripp, G., & Scheres, A. (2010). Identifying the neurobiology of altered reinforcement sensitivity in ADHD: A review and research agenda. Neuroscience and Biobehavioral Reviews, 34(5), 744-754. doi:10.1016/j.neubiorev.2009.11.021
Stavropoulos, K. K., & Carver, L. J. (2018). Oscillatory rhythm of reward: Anticipation and processing of rewards in children with and without autism. Molecular Autism, 9(1), 4. doi:10.1186/s13229-018-0189-5

The notorious evening chronotype and my master’s thesis

Posted on May 8, 2020May 11, 2020 by Dina Sarsembayeva

Almost every person, healthy or not, suffers from occasional problems with sleep and circadian rhythm. In the modern days of 24/7 smartphone use and transcontinental flights, our internal body clock is having a hard time adjusting to the external cues. For the persons suffering from mental health issues, their impaired sleep cycle can be one of the cornerstone problems of daily living. Sleep problems have been confirmed to be a first symptom, consequence, or even a cause of such psychiatric conditions as major depression, bipolar disorder, ADHD, autism, substance abuse, and even aggressive behaviour. Their strong relations, however, have not been studied systematically and broadly just yet.

Why study the circadian rhythm?

Circadian rhythm is our inner clock that regulates a lot of important processes in the human body, including the sleep/wake cycle, the release of hormones and even the way we process medicines. This clock is run by the brain region called the hypothalamus, which piles up a protein called CLK (referring to “clock”), during the daytime. CLK, in turn, activates the genes which make us stay awake, but also gradually increases the creation of another protein called PER. When we have a lot PER, it turns off CLK production and makes us ready to sleep. As CLK is getting lower, this causes a decrease in PER, so that the process starts again with elevating CLK waking us up. This cycle happens at around 24-hour intervals and is greatly influenced by so-called zeitgebers, or time-givers, like light, food, noise and temperature. When our retina neurons catch light waves, the suprachiasmatic nucleus in our brain stops the production of the hormone called melatonin that induces sleep and starts producing noradrenaline and vasopressin instead to wake us. This is the exact reason why you cannot fall asleep after watching a movie at night.

*Figure 1. The smart protein CLK wakes us up and its friend PER gets us to sleep.*

Sometimes our body clock fails to function, as in the case of jetlag when we feel bad after changing a time zone or social jetlag when we have to start work early at 8 am. It can go as far as a circadian rhythm disorder meaning you have either a delay or advancement of sleep phases or an irregular or even non-24-hour daily activities preference. However, in the general population, a small variation in the rhythm is quite normal and is usually referred to as a chronotype. It defines your preference of when to go to sleep and do your daily activities and is divided into 3 distinct versions. The radical points of these variations include a morning chronotype, or “larks”, who go somewhat 2-3 hours ahead of the balanced rhythm, and an evening chronotype, or “owls”, who are a little delayed. The larks feel and function better during the first half of the day and go to bed rather early, while the owls prefer to work in the evenings and go to bed and wake up naturally late. The third chronotype is the in-between, balanced version of these two.

arjan-stalpers-itBTNoD1PpA-unsplash — *Figure 2. The ‘owls’ seem to have questionable personalities and suffer from psychiatric conditions more often!*

What’s my study about?

Previous research has shown that many psychopathologies are linked to an evening circadian preference. For my master thesis research, I am investigating whether we can identify specific profiles in sleep and circadian rhythm problems that are linked to specific mental health problems. There was even a curious study where researchers linked the Dark Triad personalities, which include people with tendencies for manipulation, lack of empathy, and narcissism, to the evening chronotype. Maybe this leaves some evidence for the famous quote that “evil does not rest”. However, there’s a great variation in sleep duration and perceived quality of sleep in patients with various diseases. We hope to divide such persons into more or less accurate groups with a sleep profile that would predict and aid the correct diagnosis of one or the other mental health condition.

The psychopathologies are included in our study as so-called dimensions, which look at each psychiatric syndrome not as with a norm/pathology cut-off but rather as a continuum of symptoms severity. This approach allows us to see if the sleep/circadian profile we identify refers to mental health in general or can be a distinguished part of a certain psychiatric condition. It might be that all dimensions, like depression and autistic spectrum disorders, have an evening chronotype and some non-specific sleep problems. Alternatively, we might find out that a person with symptoms of depression would sleep more or less than average and go to bed later, whereas a person with anxiety would go to sleep later as well but wake up at night very often despite an average summed up sleep duration.

The circadian rhythm changes throughout a lifetime from an early to an evening chronotype towards adolescence and then gradually shift back to the earlier preference with older age. Across the whole lifespan people constantly face varying quality of night sleep. Moreover, each psychiatric condition has a particular age of onset and sometimes changes its character with time. These are the reasons why our study will also look at how the sleep/circadian profiles change within the development phases from children (4-12 years) to adolescents (13-18) to adults (19-64) to the elderly (≥65) and if they affect males and females differently.

Why would it matter?

Should we discover distinct links between the profiles of sleep/circadian problems and certain conditions, other studies can then look into whether these profiles could be the reasons behind developing a mental health condition. It’d be interesting to finally learn what is a chicken and an egg in each profile-disease relation. For instance, should we really treat ADHD patients with melatonin and bright-light lamps instead of stimulants?

sabri-tuzcu-KHBvwAnWFmc-unsplash — *Figure 3. Maybe if we adopt a typical cat’s lifestyle, we get less mental health problems. 🙂*

Dina Sarsembayeva is a neurologist and a research master’s student at the University of Groningen. She is using the data from the CoCa project to learn if the chronotypes and sleep problems can be turned into profiles to predict specific psychiatric conditions.

Further reading

Walker, W. H., Walton, J. C., DeVries, A. C. & Nelson, R. J. Circadian rhythm disruption and mental health. Transl. Psychiatry 10, (2020).
Logan, R. W. & McClung, C. A. Rhythms of life: circadian disruption and brain disorders across the lifespan. Nature Reviews Neuroscience vol. 20 49–65 (2019).
Jones, S. G. & Benca, R. M. Circadian disruption in psychiatric disorders. Sleep Med. Clin. 10, 481–493 (2015).
Taylor, B. J. & Hasler, B. P. Chronotype and Mental Health: Recent Advances. Curr. Psychiatry Rep. 20, (2018).

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

Posted on February 3, 2020February 3, 2020 by Jeanette Mostert

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

Food & mental health: the Eat2beNICE project

Posted on November 18, 2019 by Jeanette Mostert

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

Are you genetically determined to act aggressively?

Posted on March 25, 2019June 27, 2019 by Mariliis Vaht

From road rage and bar fights to terror attacks and global confrontations, humans tend to be an aggressive species. On the average, members of the same species cause only 0.3 percent of deaths among mammals [1]. Astoundingly, in Homo sapiens the rate is around 2% (1 in 50), nearly 7 times higher! There are two crucial aspects that favor this kind of behavior: dwelling in social groups and being ferociously territorial. The chances are that struggle for various resources like suitable habitat, mates and food played a key role in shaping aggression in humans, favoring genetic variants that promote aggression and therefore increase changes of survival. Indeed, anthropologists who lived with exceptionally violent hunter-gatherers found that men who committed acts of homicide had more children, as they were more likely to survive and have more offspring [2]. This lethal legacy may be the reason we are here today.

You probably know some people that could be characterized as “having a short fuse”. Perhaps you have even pondered why they seem to have such a hard time to keep their temper in check? Indeed – while scientists have known for decades that aggression is hereditary, there is another crucial component to those angry flare-ups: self-control. In humans, the impulses to react violently stem from the ancient structures located deep within the brain. The part capable of controlling those impulses is evolutionally much younger and located just behind the forehead – the frontal lobes. Unfortunately, this “top-down” conscious control of aggressive impulses is slower to act compared to the circuits of eruptive violence deep in the brain.

People who are genetically predisposed toward aggression actually usually behave more violently than the average only when provoked. People not genetically susceptible to violent outbursts seem to be better able to remain calm and “brush it off”. The ones who are predisposed in fact try hard to control their anger, but have inefficient functioning in brain regions that control emotions – in the frontal lobes [2]. Several studies have found that men genetically susceptible to act aggressively are especially likely to engage in violence and other antisocial behavior if they were exposed to childhood abuse [3]. Again, we see that although genes may carry certain predispositions, there are essential environmental aspects that determine the final outcome.

Early physical aggression needs to be dealt with care. Long-term studies of physical aggression clearly indicate that most children, adolescent and even adults eventually learn to use alternatives to physical aggression [4]. Still, the importance of proper guidance and favorable environment cannot be understated. As mentioned before, Homo sapiens have been found to cause 2 percent of deaths among their fellows. However, this has fluctuated substantially throughout the history and in different cultures. During the medieval period, human-on-human violence was responsible for stunning 12 percent of recorded deaths. For the last century, people have been relatively peaceable compared to the Middle Ages, violence being the cause of death in just 1.33 percent of fatalities worldwide. In the least violent parts of the world today, the homicide rates are as low as 0.01 percent [1].

Our brains have evolved to monitor for danger and spark aggression in response to any perceived hazard as a defense mechanism. Aggression is part of the normal behavioral repertoire of most, if not all, species; however, when expressed in humans in the wrong context, aggression leads to social maladjustment and crime [5]. By identifying genes and brain mechanisms that predispose people to the risk of being violent – even if the risk is small – we may eventually be able to tailor prevention programs to those who need them most.

References

[1] Gómez, J. M., Verdú, M., González-Megías, A., Méndez, M. (2016). The phylogenetic roots of human lethal violence. Nature 538(7624), 233–237.

[2] Denson, T. F., Dobson-Stone, C., Ronay, R., von Hippel, W., Schira, M. M. (2014). A functional polymorphism of the MAOA gene is associated with neural responses to induced anger control. J Cogn Neurosci 26(7), 1418–1427.

[3] Cicchetti, D., Rogosch, F. A., Thibodeau, E. L. (2014). The effects of child maltreatment on early signs of antisocial behavior: Genetic moderation by Tryptophan Hydroxylase, Serotonin Transporter, and Monoamine Oxidase-A-Genes. Dev Psychopathol 24(3), 907–928.

[4] Lacourse, E., Boivin, M., Brendgen, M., Petitclerc, A., Girard, A., Vitaro, F., Paquin, S., Ouellet-Morin, I., Dionne, G., Tremblay, R. E. (2014). A longitudinal twin study of physical aggression during early childhood: Evidence for a developmentally dynamic genome. Psychol Med 44(12):2617–2627.

[5] Asherson, P., Cormand, B. (2016). The genetics of aggression: Where are we now? Am J Med Genet B Neuropsychiatr Genet 171(5), 559–561.

About the author:

Mariliis Vaht, PhD

Research Fellow of Neuropsychopharmacology at Institute of Psychology, University of Tartu, Estonia. Area of research: genetic and environmental factors in longitudinal health study designs.

Who is the average patient with ADHD?

Posted on March 6, 2019June 27, 2019 by thomaswolfers

Is there an ‘average ADHD brain’? Our research group (from the Radboudumc in Nijmegen) shows that the average patient with ADHD does not exist biologically. These findings were recently published in the journal. Psychological Medicine.

Most biological psychiatry research heavily relies on so-called case-control comparisons. In this approach a group of patients with for instance ADHD is compared against a group of healthy individuals on a number of biological variables. If significant group effects are observed those are related to for instance the diagnosis ADHD. This often results in statements such as individuals with ADHD show differences in certain brain structures. While our results are in line with those earlier detected group effects, we clearly show that a simple comparison of these effects disguises individual differences between patients with the same mental disorder.

Modelling individual brains

In order to show this, we developed a technique called ‘normative modelling’ which allows us to map the brain of each individual patient against typical development. In this way we can see that individual differences in brain structure across individuals with ADHD are far greater than previously anticipated. In future, we hope that this approach provides important insights and sound evidence for an individualized approach to mental healthcare for ADHD and other mental disorders.

Individual differences in ADHD

When we studied the brain scans of individual patients, the differences between those were substantial. Only a few identical abnormalities in the brain occurred in more than two percent of patients. Marquand: “The brains of individuals with ADHD deviate so much from the average that the average has little to say about what might be occurring in the brain of an individual.”

Personalized diagnosis of ADHD

The research shows that almost every patient with ADHD has her or his own biological profile. The current method of making a diagnosis of psychiatric disorders based on symptoms is therefore not sufficient, the authors say: “Variation between patients is reflected in the brain, but despite this enormous variation all these people get the same diagnosis. Thus, we cannot achieve a better understanding of the biology behind ADHD by studying the average patient. We need to understand for each individual what the causes of a disorder may be. Insights based on research at group level say little about the individual patient.”

Re-conceptualize mental disorders

The researchers want to make a fingerprint of individual brains on the basis of differences in relation to the healthy range. Wolfers: “Psychiatrists and psychologists know very well that each patient is an individual with her or his own tale, history and biology. Nevertheless, we use diagnostic models that largely ignore these differences. Here, we raise this issue by showing that the average patient has limited informative value and by including biological, symptomatic and demographic information into our models. In future we hope that this kinds of models will help us to re-conceptualize mental disorders such as ADHD.”

Further reading

Wolfers, T., Beckmann, C.F., Hoogman, M., Buitelaar, J.K., Franke, B., Marquand, A.F. (2019). Individual differences v. the average patient: mapping the heterogeneity in ADHD using normative models. Psychological Medicine, https://doi.org/10.1017/S0033291719000084 .

This blog was written by Thomas Wolfers and Andre Marquand from the Radboudumc and Donders Institute for Brain, Cognition and Behaviour in Nijmegen, The Netherlands. On 15 March 2019 Thomas Wolfers will defend his doctoral thesis entitled ‘Towards precision medicine in psychiatry’ at the Radboud university in Nijmegen. You can find his thesis at http://www.thomaswolfers.com

How can we make sense of comorbidity?

Posted on August 10, 2016August 10, 2016 by janhaavik

Comorbidity, defined as the simultaneous occurrence of more than one disorder in a single patient, is commonplace in psychiatry and somatic medicine. In research, as well as in routine clinical settings.

In March 2016 the new H2020 collaborative project “CoCA” (Comorbidity in adult ADHD) was officially launched, with a 3-day kick-off meeting in Frankfurt, Germany. This ambitious project, which is coordinated by professor Andreas Reif and is co-maintaining this shared blog, will investigate multiple aspects of comorbidity in ADHD.

For instance, CoCA will “identify and validate mechanisms common to the most frequent psychiatric conditions, specifically ADHD, mood and anxiety disorders, and substance use disorders (SUD), as well as a highly prevalent somatic disorder, i.e. obesity”.

As reflected in this bold mission, most scientists trained in the biological sciences agree that studies of overlapping and concurrent phenomena may reveal some underlying common mechanisms, e.g. shared genetic or environmental risk factors.

However, particularly in psychiatry and psychology, the origins of comorbidity have been fiercely debated. Critics have argued that observed comorbidities are “artefacts” of the current diagnostic systems (Maj, Br J Psychiatry, 2005 186: 182–184).

This discussion relates to fundamental questions of how much of our scientific knowledge reflects an independent reality, or is merely a product of our own epistemological traditions. In psychiatry, the DSM and ICD classification systems have been accused of actively producing psychiatric phenomena, including artificial diagnoses and high comorbidity rates, rather than being “true” representations of underlying phenomena. Thus, the “constructivist” tradition argues that diagnostic systems are projected onto the phenomena of psychiatry, while “realists” acknowledge the presence of an independent reality of psychiatric disorders.

In an attempt to explain these concepts and their implications, psychiatric diagnoses and terminology have been termed “systems of convenience”, rather than phenomena that can be shown to be true or false per se (van Loo and Romeijn, Theor Med Bioeth. 2015, 41-60). It remains to be seen whether such philosophical clarifications will advance the ongoing debate related to the nature of medical diagnoses and their co-occurrence.

CoCA will not resolve these controversies. Neither can we expect that our new data will convince proponents of such opposing perspectives.

It is important to acknowledge the imperfections and limitations of concepts and instruments used in (psychiatric) research.

However, it may provide some comfort that similar fundamental discussions have a long tradition in other scientific disciplines, such as physics and mathematics. Rather than being portrayed as a weakness or peculiarity of psychiatric research, I consider that an active debate, with questioning and criticism is considered an essential part of a healthy scientific culture.

Hereby, you are invited to join this debate on this blog page! Wooden ruler vector

Measuring rewarding aspects of aggression

Posted on July 12, 2016July 12, 2016 by whjnorton

In his most famous book, Walden, the American author and naturalist Henry David Thoreau wrote that “many men go fishing all of their lives, without knowing it is not fish they are after”. Thus, one of the difficulties encountered when studying behaviour is to understand their underlying motivation. What makes some animals aggressive and other not when faced with the same situation? How does the brain process stimuli to generate an appropriate behavioural response?

A recent study by Golden and colleagues (Golden et al., 2016) has investigated this question in mice. They combined the resident-intruder assay (a rodent aggression test) with a condition place preference (CPP) test for reward behaviour. The resident-intruder test measures the response of a mouse towards an intruder in its home cage. In this case, male CD-1 mice were allowed to interact with a subordinate C57BL/BJ intruder. Aggressive contact was recorded as the latency for CB-1 mice to attack. Interestingly, about 70% of CD-1 mice were aggressive in this setup (AGGs) and 30% were non-aggressive (NONs). The CPP pairs a neutral stimulus (in this case one side of the home cage) with a conditioned stimulus – the intruder mouse. If the conditioned stimulus is rewarding then test animals spend more time on side of the cage where it was encountered. Here, CD-1 were permitted to interact with C57BL/6J intruders on one side of the CPP setup, whereas the non-conditioned side was empty. AGGs show a positive change in preference under these conditions where NONs showed aversion – they kept away from the intruder. This suggests that AGGs find the aggressive stimulation rewarding and actively seek out the interaction with C57BL/6J.

The authors next examined the neural circuits that control this behaviour with a focus on the connection between the basal forebrain and lateral habenula. During formation of aggression mediated-CPP AGGs show increased forebrain activation (in the nucleus accumbens, diagonal band and lateral septum) with a simultaneous reduction in habenula activity. Next, state of the art optogenetic techniques were used to either activate or inhibit the habenula. Stimulation of the forebrain-habenula circuit in NONs caused a positive change in place preference, whereas inhibition of this circuit in AGGs decreased CPP: the valency of the C57BL/6J stimulus mouse had changed! Importantly, optogenetic stimulation did not alter other social behaviours, although both the intensity of aggression and the rewarding properties of cocaine were increased.

This is exciting research that has possible translational potential to other species. The habenula (and in particular its interaction with the forebrain) appears to be important in processing of stimuli that can elicit aggression. In humans, deep brain stimulation of the basal forebrain and habenula has already been achieved suggesting a possible future treatment for pathological aggression.