Nature, Nurture, or Both? What Really Shapes Our Mental Health

Mental health is often framed as something we either have or lack, written into us from birth. In this piece, Iguality ambassador Dr. Dorota Komar, an epigenetics researcher, unpacks what the science actually says: how genes, environment and experience interact to shape our risk and resilience over a lifetime. It's a piece that speaks directly to why we do what we do at Iguality: if environments shape mental health, then building better ones is not optional, it's our responsibility.

Mental disorders constitute one of the leading causes of disability in Europe. WHO estimates that 1 in 6 people in Europe (around 140 million individuals) live with a mental health condition, ranging from mild to severe in terms of its impact on everyday life (OMS, Mental health). This is a staggering number. So why is the situation so serious?

Genetics definitely plays a role, and mental health struggles run in families. For example, the baseline lifetime risk of developing major depressive disorder is around 10–15%, and it roughly doubles if you are the child of a parent with depression, reaching 20-40% (Weissman et al., 2021).

However, there is no single “depression gene.” Instead, many different genes work together and their joint effect influence, how our brain functions and perceive the surrounding. 

The many paths from gene to mind

Some of the most studied genes include SLC6A4, which encodes the serotonin transporter. A well-known region of this gene (5-HTTLPR) has been proposed to influence stress sensitivity. Another example, BDNF, is a gene crucial for brain development and neuroplasticity. Its variant, Val66Met, has been linked to altered stress responses and increased vulnerability to depression (Wang et al., 2025).

However, the connection between genes and mental health is far more complexed. A large study published in 2025 mapped the genetic landscape across 14 psychiatric disorders, and revealed a nuanced relationship between DNA and mental health outcomes (Grotzinger et al., 2026). It showed that mental health conditions share overlapping genetic architectures. Disorders such as depression, anxiety, and PTSD grouped together in one cluster, defined by changes in the genes involved in oligodendrocyte biology - cells responsible for production of insulating myelin sheath around neurons.

Meanwhile, bipolar disorder and schizophrenia clustered into a separate group, defined by genes affecting excitatory neurons, which regulate how signals are transmitted in the brain. This show that mental health is not defined by single genes, but by how entire biological systems function in the brain. The same genetic architecture can give rise to different symptoms or diagnoses, meaning that these biological differences alone do not determine the outcome.

So what does? 

Born with vulnerability, not fate

We often talk about the heritability of mental health, which varies across disorders. But if these conditions are genetic, why don’t all children of affected parents develop them? Because genes do not determine outcomes, they shape sensitivity. The same genetic background can lead to very different trajectories depending on life experiences.

One of the most influential demonstrations of this comes from the “pup licking” experiments. Early development, first 2-3 years of our life, is a critical period for mental health development. Factors like the amount and quality of care we get from our parents, programme our behaviour. The same applies to other animals, like rats. Rat mother, the only caregiver, show love and affection by licking and grooming her pups. Offspring receiving less care show higher anxiety, poorer learning, and greater vulnerability to stress later in life. These differences are linked to epigenetic changes in the gene coding for the glucocorticoid receptor (NR3C1), which regulates the stress hormone cortisol (Weaver et al., 2004).

We are all born with the same genetic information and our DNA sequence is the same in each of our cells, at every moment of our development. However, the skin cell, liver cell, or nervous cell clearly differ in shape, look and behaviour. This is because not all genes are used. Epigenetic mechanisms determine which genes are turned on or off, where, and when. These mechanisms are influenced by the environment.

Lower maternal care leads to reduced expression of the glucocorticoid receptor, meaning the stress response is not efficiently shut down. As a result, stress lasts longer and has stronger effects. While this may be adaptive in dangerous environments, in long term it leads to “material fatigue” and increases the risk of mental health problems such as depression. Genetic variants influence how genes function, but environment determines how those genes are used. Both are essential.

Consistent with this, many environmental and social factors influence mental health risk. These include diet, physical health, and life conditions. For example, adherence to a Mediterranean diet has been associated with lower depression risk, while vitamin D deficiency has been linked to higher risk. Maternal obesity and advanced paternal age are associated with increased risk of neurodevelopmental disorders, like autism and ADHD. Childhood adversity is one of the strongest known risk factors for schizophrenia. Social factors, such as marginalization or chronic stress, are associated with higher risk of mental health problems. Even factors like irritating bowel syndrome, increase the risk for bipolar disorder ( Arango et al., 2021; Dragioti et al., 2022).

Mental health is often framed as a problem of the brain. In reality, it is shaped by forces ranging from molecules to society.

Mental health: from molecules to society

This interplay is reflected in disorders like ADHD, which has a heritability of up to 70%, yet cannot be fully explained by identified genetic variants (Brikell, Kuja-Halkola and Larsson, 2019; Faraone and Larsson, 2019). Research shows that genetic liability can influence not only the child directly, but also parental behaviour. For example, ADHD itself is a risk factor for eating disorders and substance abuse - it can increase the likelihood of environmental exposures before and during pregnancy that further elevate risk (Havdahl et al., 2022).

We are diagnosing more mental health disorders than ever in Europe. But are we actually becoming more ill - or just better at recognising it?

When society changes faster than biology

For conditions such as ADHD and autism, much of the increase is likely due to improved diagnosis, broader criteria, and greater awareness. However, for anxiety and depression, the situation appears different. Evidence suggests a real increase, especially among young people. A large Norwegian population study showed that the prevalence of anxiety and depressive symptoms in adolescents aged 13–19 nearly doubled from 15.3% (1995–1997) to 29.8% (2017–2019), with the sharpest rise occurring in recent years. Adolescent girls were particularly affected (Krokstad et al., 2022). 

Human genetics and biology has not changed substantially in the past 20 years - but our environment has. Mental health in young people may be paying the price.  Modern societal changes, especially digitalisation, social fragmentation, and economic uncertainty, appear to amplify risk.

A follow-up study identified school dissatisfaction (through desynchronisation from perceived upcoming reality rather than factors like bullying, that showed only limited relevance) and social media use as key contributors, with reduced time spent outside the home also playing a role (loneliness, separation from the nature, Brunborg et al., 2025).

Adolescence is a uniquely sensitive period. The brain is still developing, stress systems are highly reactive, and many mental disorders first emerge during this time. Early-onset conditions often persist into adulthood, meaning the current trends may have long-term consequences (Blakemore, 2019).

Misaligned speeds

Mental health does not arise from a single cause. It emerges from the constant interaction between biology and experience: between the genes we carry and the environments we navigate. Our genes have not changed in the past decades, but our environments have. If mental health problems are rising most sharply in young people, it may not be because they are more fragile, but because they are the first to fully experience a rapidly changing world. 

If the environments we create shape mental health, they can also protect it. Designing societies, communities, and everyday spaces that reduce stress, foster connection, and support development is not just an opportunity - it is our social responsibility.