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The genetic and biological bases of psychopathy

The genetic and biological bases of psychopathy

March 1, 2021

We often talk about the acts, the behavioral style and the way of interacting with people who have people who could be described as psychopaths. In spite of that, there is an issue that is even more disturbing than all these issues: how are psychopaths inside doors? What are the peculiarities of your own body that make you predisposed to psychopathy?

Trying to answer these questions is, deep down, address research about the biological basis of psychopathy .

Let's start, then, talking about what we know about its genetic characteristics.

Genetic findings about psychopathy

The greatest evidence in favor of genetics usually comes from studies of twins and adoptions. According to these studies, heritability in children or adolescents in antisocial behavior it is estimated at 30-44% .


In criminal adult subjects, there is a concordance of 69% for monozygotic twins (the same ovule, therefore almost identical genetic load) and 0.33% for dizygotic twins (two ovules), which gives conclusive evidence that there is a weight of genetics in criminal behavior above the environment. Numerous studies support these results.

It has also been shown that the Y chromosome he would be implicated in aggressiveness, attributing himself to a greater aggressiveness in men than in women, in general.

The MAO-A gene

The MAO-A gene it's up to date, the only clear example of how a particular mutation

It can alter the behavior. This altered gene was found in people suffering from a psychopathic disorder and, in addition, in abused children as children.


In other words, the alteration of this gene predisposes to violent behavior. Conversely, People who since birth have high concentrations of this gene are less likely to develop antisocial problems .

The interesting thing about this finding is that it could help explain why not all victims of abuse when they grow up do the same to other people, for example.

Neuroanatomical findings

At the end of the 90s, a study was carried out in which the brain activity of 41 normal subjects and 41 murderers was compared. It was found that criminals had less activity in the prefrontal region (the human region par excellence), which would translate into:

  • Neurologically : loss of inhibition of regions such as the amygdala, responsible (among others) for the regulation of aggressive feelings.
  • Conductually : risky behavior, irresponsible, transgressors of the rules, violent, impulsive ...
  • Socially : lack of empathy for other people.


Neurochemical findings

Numerous experiments have shown the crucial role of serotonin as a modulator of aggressive behavior, the relationship being the following: unless serotonin, more reinforced will be the aggressive behavior . Therefore it would be easy to conclude that people suffering from this disorder could have altered serotonergic pathways.

In the same way, noradrenaline, dopamine, GABA and nitric oxide would be involved in impulsive and violent behavior, although with less relevance.

Neuroendocrine findings

In the hormonal field, of which we have more conclusive evidence is insulin and testosterone. Some studies show that if we have a low level of glucose, and therefore insulin in the blood, we have more predisposition to violent and impulsive behaviors.

In the case of testosterone, we have multiple studies comparing criminals and healthy people, where they show that the amount of free testosterone in blood is increased in the first . In addition, several studies indicate that women with higher testosterone are more sexually active, competitive, male and alcohol users compared to women with low levels of it.

Psychophysiological findings

Cleckley (1976) proposed that psychopaths may have the ability to understand the literal (denotative) meaning of language, but not its emotional (connotative) meaning. They would, therefore, have an emotional deficit .

The psychopaths, in addition, would have the altered emotional reactivity since, in comparison to normal people, in situations that should feel anxiety and fear, they do not feel it.

Likewise, they also present an absence in the startle reaction to the exposure of visually unpleasant content, and very shrill and shrill beeps.

Based on all this data, it was proposed that psychopaths have a weak brain inhibitory system , and a strong activation system.This would explain his impulsiveness and his lack of ability to think about future consequences.

In conclusion...

The antisocial personality disorder is characterized by its lack of empathy and remorse to the violation of rights of others and social norms, high impulsiveness and aggressiveness ... They are subjects who will do whatever is necessary, regardless of the consequences, to achieve their purposes and personal benefits

But is the psychopath made or born? The answer is... a combination of both options . A marginal environment, where the person is born unattended, with violence, abuse, abandonment ... influences crucially. However, it has been shown by numerous studies, that there is more genetic weight.

A clear proof of this would be obtained through the question ... why are there people who, in the face of mistreatment, turn into abusers, while others do not? This answer would be given by the amount of gen mao-A that person has base. It could also respond to many other situations in which there are people who succumb to the situation and commit violent acts, while others refuse to do so.

We conclude then, a clear and evident biological role of the brain in antisocial personality disorder and a genetic-environment interaction (with more genetic relevance).

Bibliographic references:

  • Caspi, A., McClay, J .; Moffitt, T., Mill, J. and Martin, J. (2002). Role of genotype in the cycle of violence in maltreated children. American Association for the Advancement of Science. 297 (5582): 851-854.
  • Garrido, V. (2003). Psychopaths and other violent criminals. Valencia: Tirant lo Blanch.
  • Ros, S., Peris, M.D. and Gracia, R. (2003) Impulsivity. Barcelona: Ars Medica.
  • American Psychiatric Association, APA (2002). DSM-IV-TR. Diagnostic and Statistical Manual of Mental Disorders. Revised text Barcelona: Masson.
  • Francisco, J. (2000). Biological bases of psychopathologies. Madrid: Pyramid Psychology.
  • World Health Organization (1998). ICD-10. Mental and behavioral disorders Multiaxial version for adults. Geneva: WHO.
  • Pelegr√≠n, C. and Tirapu, J. (2003). Neurobiological bases of aggression. Intersalud. Excerpted from: //hdl.handle.net/10401/2411

Neuroscience and the Psychopath Inside with James Fallon (March 2021).


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