9 April 2018

Reduced problem behaviour because of a well-functioning mineralocorticoid receptor (MR)

Problem behaviour in young people: this substance makes the difference

We all have it: the mineralocorticoid receptor (also known as MR). Most people will never have heard of it. Nonetheless, this protein is pivotal regarding whether or not you experience depression or demonstrate problem behaviour. Utrecht researcher Hinke Endedijk studies the influence of MR on the social development of adolescents.  

Endedijk is certainly not the first to study the MR. A lot is known about it already. We have learnt, for instance, that the receptor plays an important role with regard to the consequences of stress; it has a protective function. When someone experiences severe stress and that person has a well-functioning MR, they are less likely to experience depression. Endedijk’s research goes a step further. The Utrecht University and UMC Utrecht research team wants to know what impact the MR has on the development of social behaviour in adolescents.  

Photo: Ed van Rijswijk

When someone experiences a lot of stress in their early childhood, this will affect the way they react to stress in later life. They may, for instance, react much stronger to stress: a rapid heartbeat, increased sweating and slower recovery from stress or, reversely, they might experience a flatter reaction to stress. It may also influence brain development; the prefrontal cortex at the front of your head. This will still be developing in adolescents and is important for their higher cognitive functions, e.g. planning, memory, concentration and social behaviour, such as curbing your behaviour. Endedijk: "If, as it seems, early behaviour also has an impact on the development of the prefrontal cortex, it is also plausible that adolescents who experienced a lot of stress when they were younger turn out to be les socially adept. We, therefore, expect that it has an impact on social behaviour too, but this is still a hypothesis. Is this really the case?"

Stress induced by parents

Endedijk has access to a large set of data from the Radar study of Utrecht University and Vrije Universiteit Amsterdam. This study follows the way a group of adolescents have developed over 14 years. Each year, the participants complete various questionnaires, e.g. about depression, anxiety and social behaviour. A large number have also contributed genetic data via their saliva. This genetic material has been studied for the manifestation of the MR regarding whether it is well-functioning or not. The questionnaires provide Endedijk with information about the extent to which the adolescents have experienced stress during adolescence and the way their social behaviour develops.

Foto: Ed van Rijswijk

Endedijk: "In order to measure stress in young people during adolescence, we looked into the psychological control exacted by their parents." Parents who exact a lot of psychological control tend to regularly interrupt their children, try to change their feelings or ideas, blame them for the problems of other members of the family, or keep going on about previous mistakes. "If adolescents experience this in an extreme measure, this can be very stressful. This psychological control, therefore, is an instrument to measure the stress that is being experienced."

"We study the functioning of the MR and the social behaviour of youngsters who experience stress. Does the studied person have a well or rather less well functioning MR? And do they show problem behaviour, such as unempathetic behaviour, not being able to gain perspective, or not helping others? These are very normal things that in our daily lives we all show to a certain extent and that make us more or less successful in our dealings with others and in establishing and maintaining friendships."

Despite the high level of psychological control by their parents, adolescents who have a well-functioning MR show less problem behaviour.

Less problem behaviour

Endedijk discovered that the MR has a protective function in the social behaviour of adolescents who experience a high level of psychological control from their parents; parents who monitor their adolescents extremely closely. "Despite the high level of psychological control by their parents, adolescents who have a well-functioning MR show less problem behaviour." Endedijk also suspects that the MR works more protectively in women than in men, as the female hormones oestrogen and progesterone interact with the MR. Previous research demonstrates that the MR works particularly protectively in women with regard to their chances of experiencing depression or anxiety complaints. This difference between boys and girls was not significant with regard to the effect on their social behaviour.

Kernelementen van Cognitieve Gedragstherapie in de preventie van depressie in adolescenten

The role of gender is currently being further investigated. By measuring the level of psychological control, the researchers now know whether these youngsters experienced stress during adolescence. However, these adolescents do not necessarily have to have experienced stress in their younger years. According to some theories, stress in the early years in particular is important to their later behaviour. "If we study traumatic stress during childhood, we may have a stronger instrument to prove the difference in gender", according to Endedijk. Additional questionnaires, therefore, have now been added to the Radar study in which it is asked retrospectively after traumatic events during early childhood. This refers to severe traumas such as physical and/or sexual abuse. "The outcomes of these data have only just come in and will be analysed in the coming period."

Greater certainty

Endedijk works in a multidisciplinary team in which various research areas work towards solving the same research question. Among others, Endedijk works with Angela Sarabdjitsingh of the Rudolf Magnus Brain Centre. Endedijk: "We study the same research questions, she does so in rats and I do in adolescents. We look into the same process and measure similar variables/concepts." Social behaviour in rats is, however, different from that in humans. "That is what makes it difficult to combine both studies into one publication. In practice, it means that we conduct our studies separately from each other. However, we discuss and compare the dates, outcomes and conclusions, and we have found that insights from one discipline can be of much use to the other."

"Research on humans has many limitations. You can, for instance, only look back on someone’s life by asking them about it. We have to work with people’s experiences and do not know when a possible trauma took place and how intense it really was." Angela’s rat studies constitute a valuable contribution as these allow for more control over external factors. All rats are exposed to exactly the same circumstances, such as the amount of stress. Rats that experienced stress when they were young will subsequently be offered social tasks during the age of puberty. The effects are clearer in such controlled surroundings.  

"The limitations of my human study can be solved by the rat research"

Human research is often combined with rat studies as the brain of rats resembles the human brain. Endedijk: "To a limited extent, we can translate the rat results to humans. The limitations of my human study can be solved by the rat research. In this way, we can with greater certainty explain how something works in human beings. The rat studies provide us with more insight into the underlying mechanism, in how it exactly works."

"I have always collaborated with other research areas but never with such a different one as Angela’s. I am, however, used to working with people whose exact research activities I often find difficult to understand. I really have to read up on their area of expertise to be able to understand it, which is rather valuable. It teaches me to look at research from a different perspective. It helps me, if only to refrain from being too narrowly focused and instead to see things in a wider context."

Foto: Steven Snoep

More insight into development

To the question of why this research is important, Endedijk answers: "It provides us with more insight into the origin and development of psychological diseases, such as depression and anxiety disorders. By way of a long-term study, in particular, we can find out whether people who experienced stress early on in life become more anxious or less social at the beginning of their adolescence and whether this increases during adolescence. This will allow us to really learn more about the developmental tracks of youngsters and intervene in time to prevent something worse."

In this research project, Hinke Endedijk collaborates with Professor Susan Branje and lead researcher Dr Angela Sarabdjitsingh.

Dynamics of Youth

In dealing with social problems, you need to start with the children. Utrecht University invests in resilient youth. Within the research theme Dynamics of Youth, scientists from all fields of expertise work together in order to better understand child development. How can we help young people to grow and thrive in our rapidly changing society? 

Further reading