The Role of Genetics and Environment in Childhood Behaviour Problems

When a child throws frequent tantrums, struggles with attention, or shows persistent aggression, the first question many people ask is: “Is it something they were born with, or is it because of their environment?” The answer, backed by decades of research, is both. Childhood behaviour problems arise from a complex interplay between a child’s genetic makeup and the environment they grow up in. Understanding this relationship is essential for parents, educators, and mental health professionals who want to support children effectively.

What are childhood behaviour problems? 🔗

Childhood behaviour problems cover a wide range of challenges, from defiance and opposition to aggression, impulsivity, attention difficulties, and emotional dysregulation. These behaviours can show up early – sometimes as young as toddlerhood – and, if left unaddressed, may persist into adolescence and adulthood. Research on externalising behaviours shows that these issues often include temper tantrums, defiance, and aggression in childhood, which can later manifest as substance use and other risky behaviours in adolescence. The key point is that these problems are rarely caused by a single factor. They emerge from the dynamic relationship between a child’s biology and their life experiences.

The genetic foundation of behaviour 🔗

Every child inherits a unique set of genes from their parents, and these genes influence the development of their brain, nervous system, and temperament. Some children are born with a genetic predisposition toward certain behavioural traits – such as heightened impulsivity, emotional reactivity, or difficulty with self-regulation. This does not mean they are destined to develop behaviour problems, but it does mean they may be more vulnerable under certain conditions.

Heritability of behavioural traits 🔗

Twin studies have been instrumental in showing how much genetics contribute to behavioural differences. Behavioural genetics research consistently finds that monozygotic (identical) twins, who share 100% of their DNA, show greater similarity in behaviour compared to dizygotic (fraternal) twins, who share roughly 50%. This difference suggests that genetic factors play a substantial role in shaping traits related to behaviour problems. However, heritability is not a fixed number – it changes depending on the environment. For instance, studies have found that in families with fewer socioeconomic resources, shared environmental factors account for most of the variation in children’s abilities, whereas in wealthier families, genetic influences are more dominant. This is a powerful example of how genes and environments are deeply intertwined.

Polygenic influences 🔗

Behavioural traits are not controlled by a single gene. Instead, they are polygenic – influenced by the combined effects of many genes, each contributing a small amount. Researchers now use polygenic scores to measure a person’s overall genetic propensity for traits like educational attainment, cognitive ability, or externalising behaviour. These scores aggregate hundreds or thousands of DNA variants to provide a snapshot of genetic risk. However, having a high polygenic score for a particular trait does not guarantee that the trait will develop – it simply indicates a higher probability, one that depends heavily on environmental conditions.

Neurotransmitters and their role in behaviour 🔗

At the biological level, behaviour is deeply influenced by neurotransmitters – the chemical messengers that carry signals between nerve cells in the brain. According to the National Library of Medicine, these chemicals are crucial for regulating emotions, thoughts, memory, movements, and sleep patterns, and disruptions in their balance are linked to a range of neurological and psychiatric conditions.

Dopamine 🔗

Dopamine plays a central role in reward processing, motivation, motor control, and executive functioning. Dysregulation of dopamine pathways has been linked to conditions including attention-deficit hyperactivity disorder (ADHD), Tourette syndrome, and psychosis. Children with genetic variations affecting dopamine signalling may have difficulty sustaining attention, controlling impulses, or regulating their responses to reward and punishment.

Serotonin 🔗

Serotonin is essential for mood regulation, emotional processing, and impulse control. Low levels of serotonin have long been associated with depression, anxiety, and aggressive behaviour. In children, serotonin imbalances can manifest as irritability, persistent sadness, or difficulty managing emotions. Research into selective serotonin reuptake inhibitors (SSRIs) has deepened our understanding of how this neurotransmitter shapes mental health across the lifespan.

Norepinephrine and GABA 🔗

Norepinephrine influences attention, stress responses, and arousal. Dysfunction in norepinephrine pathways has been implicated in anxiety disorders, ADHD, mood disorders, and post-traumatic stress disorder. Meanwhile, gamma-aminobutyric acid (GABA) serves as the brain’s primary inhibitory neurotransmitter, helping to calm neural activity. When GABA functioning is disrupted, it can contribute to anxiety, epilepsy, and behavioural dysregulation in children.

The important takeaway is that neurotransmitter systems are not static – they develop and change throughout childhood and adolescence. Research on monoamine neurotransmitter development highlights that these systems continue maturing well into early adulthood, which means that early experiences can shape how they function for years to come.

Major brain structures and child behaviour 🔗

The brain develops from three primary divisions during embryonic life – the hindbrain, the midbrain, and the forebrain. Each of these regions plays distinct roles that are relevant to understanding childhood behaviour.

The hindbrain 🔗

The hindbrain, located at the base of the brain, includes the medulla oblongata, the pons, and the cerebellum. It is responsible for managing essential autonomic functions such as breathing, heart rate, and digestion, as well as coordination, balance, and movement. The cerebellum, often called the “little brain,” is critical for motor learning and procedural memory. Disruptions in hindbrain development can affect a child’s basic motor coordination and physiological regulation, which may indirectly contribute to behavioural difficulties.

The midbrain 🔗

The midbrain acts as a relay station between the hindbrain and forebrain, processing auditory and visual information and playing a role in arousal, movement, and pain regulation. It contains the substantia nigra, a structure that is rich in dopaminergic neurons. Abnormalities in this region can affect a child’s motor control, alertness, and response to sensory stimuli – all of which have downstream effects on behaviour.

The forebrain 🔗

The forebrain is the largest and most complex brain division, containing the cerebrum, the thalamus, the hypothalamus, the hippocampus, and the amygdala. It is responsible for higher cognitive functions like thinking, language, emotional regulation, memory, and decision-making. The prefrontal cortex, a forebrain structure, is especially important for impulse control and planning – areas where children with behaviour problems often struggle. The amygdala, another forebrain structure, processes fear and emotional memories and is central to anxiety and threat-related responses. Children who have experienced early trauma often show heightened amygdala reactivity, making them more prone to emotional and behavioural difficulties.

Gene-environment interaction: where biology meets experience 🔗

One of the most important concepts in understanding childhood behaviour problems is gene-environment interaction (GxE). This refers to situations where the effect of a genetic predisposition on behaviour depends on the type of environment a child is exposed to – and vice versa.

The classic MAOA study 🔗

One of the most well-known examples comes from the Dunedin Longitudinal Study, led by Avshalom Caspi and colleagues. They found that children who carried a genetic variant linked to low activity of the enzyme monoamine oxidase A (MAOA) and were also maltreated during childhood were significantly more likely to develop antisocial and aggressive behaviour than children who had only one of these risk factors. Research has confirmed that children with this genetic deficiency appear especially vulnerable to the effects of physical maltreatment. This finding has been replicated across multiple samples worldwide, powerfully illustrating that neither genes nor environment alone determine outcomes – it is their combination that matters.

Gene-environment correlation 🔗

Beyond interaction, genes and environments are also correlated in important ways. There are three main types of gene-environment correlation. Passive correlation occurs when parents pass on both their genes and the home environment – for example, a parent with a genetic tendency toward anxiety may create a more anxious household. Evocative correlation occurs when a child’s genetically influenced behaviour draws specific responses from the environment – an impulsive child may elicit harsher discipline, which in turn worsens their behaviour. Active correlation occurs when children seek out environments that match their genetic dispositions, such as a sensation-seeking child gravitating toward risky activities.

Epigenetics: how experiences change gene expression 🔗

Perhaps the most striking discovery in recent decades is that environmental experiences can literally change how genes function – without altering the DNA sequence itself. This is the field of epigenetics. According to Harvard University’s Center on the Developing Child, early experiences cause chemical marks to accumulate on our DNA, forming what is known as the “epigenome.” These marks determine how much or how little of specific genes are expressed. Harmful experiences such as malnutrition, toxic stress, or exposure to drugs can create epigenetic changes that increase the risk of behavioural and mental health problems later in life. Crucially, research also shows that positive environmental factors – supportive relationships, stable caregiving, and therapeutic interventions – can promote beneficial epigenetic modifications that build resilience. This means that even children who carry genetic risk factors can be protected through high-quality environments and early intervention.

The role of family and environment 🔗

Family relationships are one of the most powerful environmental forces shaping child behaviour. Research on family relationships and child adjustment consistently shows that parental warmth and support are linked to better outcomes, while harsh or negative parenting is tied to the development of emotional and behavioural problems. However, genetically informed studies reveal that this relationship is not purely environmental. Parents’ own genetic traits influence their parenting style, and children’s genetically influenced temperaments shape how parents respond to them. This creates a feedback loop where genes and environment continuously influence each other.

Beyond the family, broader environmental factors also play a role. Socioeconomic deprivation, neighbourhood violence, school climate, peer relationships, and exposure to toxins all interact with a child’s genetic profile to shape developmental outcomes. No single environmental factor is responsible; rather, numerous small influences accumulate – a concept researchers call polyenvironicity.

Why a holistic approach matters 🔗

Given the deeply interconnected nature of genes and environment, addressing childhood behaviour problems requires a holistic perspective. Interventions that focus only on changing the child’s behaviour without considering their biological vulnerabilities – or programmes that focus only on genetics without addressing environmental stressors – will fall short.

Effective approaches include early screening for genetic and biological risk factors, nurturing and responsive caregiving practices, reducing toxic stress in the child’s environment, and providing evidence-based therapeutic interventions when problems emerge. Schools, families, healthcare providers, and policymakers all have roles to play in creating environments that support children’s healthy development – especially those who may be genetically vulnerable.

The science is clear: genes load the gun, but the environment pulls the trigger. And just as importantly, a supportive environment can keep that trigger from ever being pulled.

What do you think? How can schools and families work together to create environments that buffer children against genetic vulnerabilities for behaviour problems? And do you think society gives enough attention to the biological side of childhood behavioural challenges?

References

1. https://pmc.ncbi.nlm.nih.gov/articles/PMC9796590/
2. https://www.sciencedirect.com/topics/biochemistry-genetics-and-molecular-biology/gene-environment-interaction
3. https://www.ncbi.nlm.nih.gov/books/NBK539894/
4. https://www.sciencedirect.com/science/article/abs/pii/S0736574818302570
5. https://www.simplypsychology.org/forebrain-midbrain-hindbrain.html
6. https://pmc.ncbi.nlm.nih.gov/articles/PMC4685725/
7. https://developingchild.harvard.edu/resources/infographics/what-is-epigenetics-and-how-does-it-relate-to-child-development/
8. https://immunizenevada.org/the-neurobiology-of-mental-health-disorders/
9. https://pmc.ncbi.nlm.nih.gov/articles/PMC3233191/