Does Biology Play a Role in Domestic Abuse?

Does Biology Play a Role in Domestic Abuse?

Domestic abuse is a devastating problem nationwide. But what causes abusers to become aggressive in the first place? Does biology play a role? And should we have more compassion for abusers?

Is Abuse in Our Genes?

Are some people predisposed to becoming abusers? According to a 2002 study, genetics may indeed play a role.

The study followed 1,037 children in New Zealand, including 442 boys. These children were followed for 26 years, from birth into adulthood. Researchers examined the genetic makeup of each child, looking specifically at monoamine oxidase A, or MAOA. 

MAOA is a gene that signals the breakdown of neurotransmitters linked with mood, aggression, and pleasure. In the 1990s, researchers in the Netherlands discovered that variations in the MAOA gene were linked to aggression and violence in one Dutch family.

The New Zealand study found that some of the boys had the MAOA genetic variation and lower enzyme levels, meaning they were predisposed to violence.

However, the study also looked at the boys’ home environments. Those who had been mistreated as children (that is, who experienced physical, psychological, and/or sexual abuse) were much more likely to break the law, become violent, and end up incarcerated as adults.

In fact, 85 percent of the subjects who had both the MAOA mutation (and, therefore, low levels of the enzyme) and who were mistreated developed antisocial outcomes. 

Later studies have since confirmed the New Zealand researchers’ findings. 

Are Males More Likely to Become Abusers?

The findings are interesting for many reasons, but chief among them is the apparent focus on boys. This specific MAOA genetic variation only occurs on the X chromosome. Because children assigned female at birth have two X chromosomes, scientists believe the genetic variation on one chromosome is essentially “canceled out” by the other. Boys, however, have one X and one Y, which means a variation on the X chromosome will be prominent.

This genetic variation could also explain why females are generally less prone to violent and antisocial behaviors. 

Nature vs. Nurture

The genetic research brings another debate to the forefront: what causes abusers to become violent? Is it nature, nurture, or a combination of both?

It seems that both nature (genetics) and nurture (a child’s environment and exposure to abuse) determine whether a person will be abusive as an adult.

We already know that children who grow up in abusive environments are more likely to perform poorly in school and exhibit aggressive behaviors. (Read more about how childhood abuse impacts school and social performance here).  

However, the New Zealand study added another layer of complexity to the issue. According to the data, boys born with the genetic variation, who also experienced abuse in childhood, were nine times more likely to become abusive and/or antisocial as adults. 

Conversely, children who were abused but had high levels of the MAOA enzyme were unlikely to develop abusive behaviors as adults. 

However, the study doesn’t clarify whether early intervention can make a difference for children who both have low MAOA and experience childhood abuse. The clear conclusion from the study is that the best way to prevent violence in adulthood is to prevent child abuse from happening in the first place. 

An Explanation, But NOT an Excuse

This research may explain why some men become abusive. However, an explanation should never become an excuse.

Yes, biology and a person’s upbringing play a vital role in future outcomes. It might be easy, then, to excuse the abusive and aggressive behaviors as “not their fault.” But hear this loud and clear: there is never an excuse for abuse. 


If you or someone you know is in an abusive environment, seek help. You can contact your local domestic violence shelter or reach out to the National Domestic Violence Hotline to access expert help anonymously.

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