Beyond nature versus nurture: understanding childhood trauma

For decades, mental health research has often been framed as a debate: is it genes or environment that shape our psychological wellbeing?

As researchers, we know the answer is almost always "both". Yet we still tend to think of genetic risk and environmental experiences as separate pieces of the puzzle. My latest research made me think differently about that distinction.

Our study focused on childhood trauma, one of the most well-established risk factors for a range of mental health difficulties, including psychosis, depression and anxiety. When researchers talk about childhood trauma, we are referring to a broad range of adverse experiences that occur during childhood and adolescence, including abuse, neglect, bullying and exposure to conflict within the home. These experiences differ in important ways, but they share one common feature: they can have profound and lasting consequences throughout development. We wanted to understand whether genetic liability and childhood adversity might be linked in ways that are more complex than we usually assume.

At first glance, the idea can sound surprising. Trauma is something that happens to people. Genes are something we inherit. What could they possibly have to do with one another?

Importantly, this does not mean that trauma is ‘genetic’. Nor does it mean that children are responsible for, or somehow cause, the adversities they experience. Those interpretations would be both scientifically incorrect and ethically troubling. 

How we investigated the relationship between genes and environment

To explore this, we analysed data from two large studies: the European Network of National Schizophrenia Networks Studying Gene-Environment Interactions (EU-GEI) project, which investigates risk factors for psychosis across Europe and Brazil, and the Avon Longitudinal Study of Parents and Children (ALSPAC), a UK birth cohort that has followed thousands of individuals from childhood into adulthood.

We examined whether genetic liability for several psychiatric and behavioural traits was associated with different types of childhood trauma, including emotional abuse, physical abuse, sexual abuse, bullying and household discord.

However, it should be noted that the effects were modest. In fact, these results are exactly what we would expect. Psychiatric traits are highly complex. Neither genes nor environments act in isolation, and there is no single factor that determines who will experience adversity or develop mental health problems. Polygenic scores, the genetic measures used in our study, capture only a small proportion of overall genetic liability.

This is an important point because genetic findings are sometimes misunderstood as implying inevitability. Our results do not suggest that childhood trauma is predetermined by genetics. Rather, they reinforce the importance of environmental experiences. 

Our findings highlight the complexity of the nature versus nurture debate

One of the most important lessons from this work is that genetics and environment should not be viewed as competing explanations. They are often part of the same story.

The concept of gene-environment correlation challenges the simple narratives that have dominated discussions of mental health for so long. Instead of asking whether mental illness is caused by nature or nurture, we can begin asking a more interesting question: how do nature and nurture shape one another across development?

The answer is unlikely to be simple. But understanding that complexity may ultimately bring us closer to explaining how mental health difficulties emerge and how we might prevent them.

'Gene-Environment Correlation Across Trauma Subtypes and Developmental Timing: Evidence From the EU-GEI and ALSPAC. Trotta et al. was published in Biological Psychiatry.