What Causes ADHD?

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young boy with adhd fidgeting while learning

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  • ADHD is a disorder that can affect thinking, behavior, and your ability to function.
  • Researchers have not identified an exact reason why ADHD occurs.
  • Certain risk factors like having a family history of ADHD, brain injury, or complications during pregnancy and childbirth can make a child more likely to develop the condition.

Attention-deficit/hyperactivity disorder (ADHD) is a common neurodevelopmental disorder—meaning it’s a condition that affects the growth and development of the brain. Most people with ADHD receive their diagnosis during childhood and adolescence, but symptoms can last into adulthood.

The hallmark symptoms of ADHD are inattention, hyperactivity, and impulsivity. And while everyone experiences these symptoms from time to time, those with ADHD display these ongoing behaviors for more than six months. Eventually, ADHD can make it difficult to complete tasks, pay attention at school or work, and interact with others.

The exact cause of ADHD is not well understood. However, research on why ADHD occurs remains ongoing. Currently, experts believe that a combination of genetic and environmental factors can increase your or your child’s risk of developing the condition.

Risk Factors

Current ADHD research shows that the condition is rarely caused by a single risk factor. Both genetic and environmental factors may play a role in the development of ADHD. Studies also show that several genetic and environmental factors may compound on (or, add on to) each other, further increasing the risk of developing ADHD.


ADHD researchers theorize that genetic variations (changes) play a role in how the brain develops. Your genes can produce proteins that affect different parts of brain development, such as the production, growth, and organization of the neurons (or, nerve cells). 

When there is a mutation or variation in your genes, your brain, and its cells may not function how they should. As a result, genetic variations can interrupt how your brain:

  • Gives instructions that help your nerve cells communicate with each other
  • Produces or controls neurotransmitters (or, chemical messengers that help your brain carry information from one cell to the other)
  • Manages the connections between the neurons (also known as synapses)

That said, these interruptions may then play a role in how you think, behave, and control your environment. However, much more research is needed to better understand which genes are linked to ADHD and how genetic factors mix with environmental changes that lead to the development of ADHD.

Non-Genetic Risk Factors

Researchers are also exploring possible non-genetic factors that can boost the risk of ADHD development. These factors may include, but are not limited to:

  • Prenatal (before birth) exposure to toxins such as lead, alcohol, or secondhand cigarette smoke
  • The birthing parent experiencing extreme stress, having hyperthyroidism, or using acetaminophen and valproate (a drug that helps treat seizures) during pregnancy or childbirth 
  • Brain injury
  • Premature delivery or low birth weight

It is important to note that there are a lot of myths about the causes of neurodevelopmental conditions, like ADHD. While you may hear these myths, research does not support these views as possible causes of ADHD. These myths include:

  • Eating too much sugar
  • Consuming artificial food colorings and flavorings
  • Watching too much television
  • Bad parenting styles
  • Family chaos
  • Poverty

In certain cases, these factors may worsen ADHD symptoms, along with the symptoms of other conditions. But, there is no scientific evidence that points to these factors as direct causes of ADHD. 

Is ADHD Hereditary?

ADHD tends to run in families. If you have a first-degree relative (such as a parent or sibling) who has received a diagnosis for ADHD, your risk of developing ADHD is about nine times higher than those who do not have a family history of the condition. 

Keep in mind: having a family history of ADHD does not guarantee that you’ll develop ADHD in your lifetime, it just means that you may have an increased chance of experiencing symptoms and receiving an ADHD diagnosis.

Who Gets ADHD?

Anyone can develop ADHD, but certain groups are more likely to be diagnosed with the condition than others. The following risk factors may increase your risk of receiving an ADHD diagnosis:

  • Age: ADHD is most common in children ages 3 to 17 years old. 
  • Assigned sex at birth: Boys receive an ADHD diagnosis more often than girls. However, this does not mean that boys are more likely to have ADHD. Historically, research on ADHD has been focused on young boys. Recent studies have learned that symptoms of ADHD can look different in boys and girls (e.g., boys experience more hyperactivity, while girls experience more inactivity). More research is needed to understand exactly how symptoms present themselves in girls and women.
  • Ethnicity: Black and white children receive a diagnosis of ADHD more often than Hispanic and Asian children. 
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6 Sources
Health.com uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
  1. MedlinePlus. Attention-deficit/hyperactivity disorder.

  2. Centers for Disease Control and Prevention. What is ADHD?

  3. Faraone S, Banaschewski T, Coghill D, et al. The World Federation of ADHD international consensus statement: 208 Evidence-based conclusions about the disorder. Neurosci Biobehav Rev. 2021;128:789-818. doi:10.1016/j.neubiorev.2021.01.022

  4. American Psychiatric Association. What is ADHD?

  5. Posner J, Polanczyk GV, Sonuga-Barke E. Attention-deficit hyperactivity disorder. Lancet. 2020;395(10222):450-462. doi:10.1016/S0140-6736(19)33004-1

  6. Centers for Disease Control and Prevention. Data and statistics about ADHD.

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