Experts do not fully understand the causes of attention deficit hyperactivity disorder (ADHD) in children. Brain differences, genetics, head injuries, and environmental factors may play a role.

ADHD is a chronic neurodevelopmental condition that can cause inattention, hyperactivity, and impulsivity.

ADHD affects around 8.4% of children in the United States. Researchers are unsure what causes ADHD, but research into risk factors is ongoing.

This article looks at potential causes of ADHD in children, including brain anatomy and function, genes and heredity, head injuries, prematurity, and prenatal exposure to toxins. It also looks at factors that do not cause ADHD and the outlook for people with the condition.

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Researchers have found that the brains of people with ADHD may differ in structure and function from people without ADHD.

The differences in brain anatomy involve areas that may affect typical ADHD symptoms. However, scientists do not fully understand how these brain differences cause or contribute to ADHD.

People with ADHD may have the following differences in brain anatomy and function:

Frontal lobe

The frontal lobe is behind the forehead. It is responsible for various functions, including:

  • impulse control
  • social behavior
  • decision making
  • planning
  • paying attention

In people with ADHD, areas of the frontal lobe may mature later than usual. This could affect a person’s cognitive abilities in these functions.

Neural networks

The brain contains neurons, which are cells that communicate signals to each other through connections called synapses.

In children with ADHD, these networks may develop more slowly and communicate signals less effectively. This could affect a person’s ability to:

  • focus
  • plan
  • pay attention
  • switch attention from one task to another


Neurotransmitters are chemicals in the brain that help send signals between neurons.

The actions of certain neurotransmitters may be different in people with ADHD. This includes a disruption in the neurotransmitter dopamine. Dopamine plays a role in:

  • the brain’s reward system
  • motivation
  • emotion regulation
  • muscle movement

Learn more about neurotransmitters.

Other structural differences

Researchers found volume differences in the brains of children with ADHD. The amygdala, hippocampus, and accumbens regions of the brain may be smaller in children with ADHD. These differences may affect emotional regulation and motivation.

Read about the differences between the brains of people with and without ADHD.

Researchers believe genes and heredity are significant risk factors for ADHD. A person with parents or siblings with ADHD is more likely to have the condition.

However, the mechanisms involved in how people inherit ADHD are complex. Researchers do not believe they relate to a specific gene difference.

Scientists have not linked a specific gene or combination of genes with ADHD and do not fully understand how genetic changes cause ADHD.

Read more about ADHD and heredity.

Various research has found that traumatic brain injury (TBI) may lead to an increased risk of ADHD. A person may experience this type of injury after a violent blow, jolt, or bump to the head or body, or from an object that pierces the skull.

Researchers have also found that the risk of ADHD in children may increase with the severity of the injury.

One 2018 study found that 13 of 21 children in the study who experienced a severe TBI later developed ADHD. While most children developed ADHD within 18 months of their injury, some children only showed signs of ADHD as late as 7 years later.

A severe TBI can affect a single region or a widespread region of the brain. The bleeding, inflammation, swelling, or damage to nerve cells from a TBI may alter the structure and functioning of the brain, which may contribute to or cause ADHD.

Researchers associate preterm birth with a higher risk of ADHD.

According to a 2018 study that included 113,227 children, preterm birth may have stronger links to the inattention aspects of ADHD than hyperactivity.

Scientists do not fully understand the links between preterm birth and ADHD. However, they believe being born before 35 weeks, a critical period of in utero development, means the brain may be immature and underdeveloped.

The lack of development or changes to the brain may contribute to the development of ADHD.

According to a 2023 review of previous research, exposure to toxins, such as sulfur dioxide, nitrogen dioxide, and particulate matter in air pollution, may worsen or cause ADHD in children.

Prenatal and early exposure to particulate matter can reduce the volume of children’s brains, reduce the ability to think, and lead to behavioral difficulties. Prenatal exposure to particulate matter may also reduce white matter in the brain and increase a child’s risk of ADHD.

Researchers especially link toxin exposure with ADHD symptoms such as hyperactivity and developmental delays.

Anecdotally, people link various factors with a higher risk of ADHD, such as:

  • eating high amounts of sugar
  • a “chaotic” family environment
  • watching a lot of television
  • parenting styles
  • living in poverty

Although these factors may worsen ADHD symptoms in children, no reliable evidence suggests they can cause ADHD.

ADHD is a chronic disorder, meaning there is no cure. However, treatment can effectively manage it. Learning specific strategies and techniques can help a person cope.

Treatment may include medication, psychotherapy, or a combination. It can help a person manage their symptoms and reduce ADHD’s effects on their schooling, daily life, and relationships.

Scientists do not fully understand the causes of ADHD. However, they believe differences in the structure and function of the brain, genetics, TBI, preterm birth, and prenatal toxin exposure may contribute to the condition.

Although there is no cure for ADHD, people can manage the symptoms and minimize their effects through medication, therapy, and management strategies.