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Antisocial behaviour, or behaviour deviating from society’s norms, can have unpleasant consequences for several parties. Dr. Katre Sakala, a from Tallinn University‘s School of Natural Sciences and Health, investigated the early (biological) risk factors of antisocial behaviour in her doctoral thesis.
The concept of antisocial behaviour, or behaviour that does not meet societal norms, refers to a very wide and diverse set of behaviours, including clinical disorders. Therefore, there are many different reasons why some people behave antisocially. In her doctoral thesis, Katre Sakala focused on two characteristics of antisocial behaviour that deviates from society’s norms: behaviour of the investigated subject that led to police intervention and drug use. The research is based on the longitudinal data set of the Estonian Children Personality Behaviour and Health Study (ECPBHS), which enables long-term observation of people’s behaviour.
Previous studies have shown that ADHD diagnosed in childhood is related to antisocial behaviour. Sakala did not base her research on diagnosis, but on symptoms of ADHD. As a result of her research, she found that the strongest forecasters of later behaviour that does not take into account societal norms were substance use disorder, reactive aggression, difficulty concentrating at age 15 and fights in elementary school. Considering the occurring concentration difficulties that many people already have at school (without aggressive behaviour) as a risk factor, this knowledge may later help prevent antisocial behaviour.
Among the biological risk factors, Sakala focused on the association of monoamine oxidase, or MAO, with antisocial behaviour. Monoamine oxidase is an enzyme that helps break down serotonin and dopamine, both of which affect people’s mood and behaviour. Analysis of the association between platelet MAO activity and problem behaviour revealed that men with lower levels of MAO may exhibit antisocial behaviour.
Females also showed a similar connection, but only when they exhibited more antisocial behaviour. It is important to note that the association between drug use and low MAO activity in platelets was only seen in men, who were also at a higher risk of starting drugs earlier. These results confirm the already existing knowledge that platelet MAO activity is associated with problematic and risky behaviour, including drug use, but for the first time this connection is also seen in the behaviour of school pupils, thanks to representative sampling and longitudinal data.
Previous research has shown that men with a specific MAOA-L genotype who have been treated badly in childhood are more impulsive and express more antisocial behaviour. Therefore, in her doctoral thesis, Sakala also investigated the possible connection between these two behaviours and the MAOA gene and its methylation (DNA methylation is the process by which a gene is silenced).
As a result of the analysis, Sakala found that even if the methylation of the MAOA gene in adolescence is related to reckless and uninhibited behaviour as well as a quick decision-making style and a desire for new experiences, this connection has only occurred in men who had a difficult home environment and the corresponding genotype.
Several scientific studies have shown that the MAOA-L genotype can be a risk factor for antisocial behaviour in men, but the previous results of the Estonian Children Personality Behaviour and Health Study (ECPBHS) have instead shown that men with the same genotype can also manage better in everyday life, so the current result may indicate that MAOA methylation can be a marker of developmental plasticity of the MAOA-L genotype, meaning that in favourable conditions, different behavioural patterns will develop than in poor ones.
In her research, Sakala found that gender was a stable predictor of antisocial behaviour, but the effect of gender was mediated by several other factors, such as drug use and aggression. The significance of monoamine oxidase as a behavioural biomarker may be gender dependent because the gene encoding the enzyme is located in the X chromosome. The results of the doctoral thesis show the association of low platelet MAO activity with problematic behaviour in men very clearly, while in women a similar connection was only evident when their behaviour was more antisocial.
Katre Sakala defended her doctorate „Antisocial behaviour and monoamine oxidases” on the 16th of May, 2024.
This article was originally published on the webpage of Tallinn University.
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