What causes attention deficit hyperactivity disorder (ADHD)?

The causes of attention deficit hyperactivity disorder (ADHD) are still not completely understood. The condition does seem to run in families and so is often thought to be inherited. Other factors, such as prenatal and childhood exposure to certain toxic substances like lead; brain injuries; smoking, drug, or alcohol use by expectant mothers; and low birth weight are also possible causes.

Dr. Mehmet Oz, MD
Cardiologist (Heart Specialist)

No one is entirely sure where attention deficit hyperactivity disorder (ADHD) comes from. There are most likely multifactorial causes. Multiple studies have connected ADHD risk with family history; exposure to tobacco smoke, toxins, or lead; maternal use of antidepressants during pregnancy; and low birthweight. However, there are many social factors that can cause a child to become more disruptive and exhibit ADHD-like symptoms. Higher levels of stress or anxiety stemming from events such as a parental divorce or teasing from other children can cause a child to "act out" at home or school and trigger a teacher to suspect ADHD.

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Attention deficit hyperactivity disorder (ADHD) affects the brain's executive function system. The executive function system plays a key role in controlling behavior, thoughts, and emotions. Weaknesses in executive function can make it difficult to control one's emotions, start and finish tasks, organize items, use long-term memory, solve problems, and work toward a goal.

While there are many theories, scientists don't know exactly what causes ADHD. It's important for parents to know that ADHD is not caused by child-rearing methods or the family environment. Scientists do know that ADHD runs in families—many people with ADHD have a parent or other relative with the disorder. Symptoms of ADHD are also seen in patients who have had brain injuries.

Despite extensive research, scientists still do not know what causes Attention Deficit Hyperactivity Disorder. Researchers, however, have ruled out some causes-such as a child's surrounding and upbringing.

Environmental factors may make a case of ADHD more pronounced, but do not cause the disorder.

Research has shown refined sugars and food additives have little or no effect on behavior.

There does seem to be a strong hereditary component to ADHD, and it is believed that prenatal exposure to alcohol and cigarettes may worsen the condition.

Dr. Edward M. Hallowell, MD
Psychiatrist (Therapist)

People with attention deficit hyperactivity disorder (ADHD) sometimes feel that they're to blame for their lack of focus or impulsivity. In this video, psychiatrist and ADHD expert Edward Hallowell, MD, discusses what's really at the root of this condition.


Constance Mofunanya, DNP
Pediatric Nursing Specialist

Attention deficit/hyperactivity disorder (ADHD) in children is a syndrome of inattention, hyperactivity and impulsivity. According to DSM-IV, there are 3 types of ADHD, predominantly inattentive, predominantly hyperactive-impulsive, and combine. The predominantly hyperactive-impulsive type occurs 2 to 9 times more in boys, but the predominantly inattentive type occurs with equal frequency in both boys and girls. ADHD is classified as a developmental disorder and is considered a disruptive behavior disorder. It is estimated that 3 to 10% of school agers are affected by ADHD. ADHD has no known single or specific cause. Possible causes include genetic, bio-chemical, sensorimotor, physiologic, and behavioral factors. Risk factors includes but not limited to, head trauma, birth weight less than 1000g, lead exposure, prenatal exposure to alcohol, cocaine and tobacco.

Scientists are studying cause(s) and risk factors in an effort to find better ways to manage and reduce the chances of a person having ADHD. The cause(s) and risk factors for ADHD are unknown, but current research shows that genetics plays an important role. Recent studies of twins link genes with ADHD. In addition to genetics, scientists are studying other possible causes and risk factors including:

  • Brain injury
  • Environmental exposures (e.g., lead)
  • Alcohol and tobacco use during pregnancy
  • Premature delivery
  • Low birth weight

Research does not support the popularly held views that ADHD is caused by eating too much sugar, watching too much television, parenting, or social and environmental factors such as poverty or family chaos. Of course, many things, including these, might make symptoms worse, especially in certain people. But the evidence is not strong enough to conclude that they are the main causes of ADHD.

Dr. Iris M. Rodriguez-Ocasio, MD

80% of ADHD cases are thought to have a polygenic basis. Neuroimaging, neuropharmacology, and neurophysiology studies have shown that there is a probability of a biologic basis.

Doctors and scientists aren’t sure what causes attention deficit hyperactivity disorder (ADHD). What they do know is that in people with ADHD, the brain works differently than it does in people without the condition. This makes it hard for people with ADHD to behave exactly the way other people do. The other thing known for a fact is that living with ADHD is tough.

While we don't know the exact cause of ADHD, (the leading hypothesis is lack of pruning of connections in the infant and adolescent brain), we do know that relatives with it have a greater preponderance—that is it has some components of genetic predispositions. If your parent or sibling has ADHD, you have a 30 percent chance of having it too.

Scientists are also looking at other potential risk factors for ADHD like maternal smoking, drug use, and alcoholism, exposure to toxins like lead in the womb or food borne pesticides.

Donna Hill Howes, RN
Family Practitioner

Attention deficit hyperactivity disorder (ADHD) is largely a brain issue. ADHD tends to be genetic in nature. If you have ADHD, your child will be more likely to have it than the average person. This means that there may be nothing you can do to prevent ADHD in your child. Your child may just be wired differently. Certain situations during childhood (like lead exposure), in the womb, and at birth may also predispose your child to ADHD. Luckily, ADHD medications and other treatments are available. Talk to your child's doctor to find out more.

Dr. Lara Honos-Webb, PhD
Psychology Specialist

You have probably been told that attention deficit hyperactivity disorder (ADHD) is first a disorder, and second a medical dysfunction related to brain pathology (a dysfunction or disease of the brain). Current explanations highlight the importance of neuropsychological deficits (a psychological problem attributed to faulty brain functioning) and brain anomalies. Though many brain regions, such as the frontal cortex and the nucleus accumbens, have been implicated in the causing of ADHD, it remains true that "unlike illnesses such as diabetes, arthritis, or epilepsy, there is no physiological or pathological evidence for ADHD. The diagnosis is entirely subjective and is based on how we interpret a collection of symptomatic behaviors." Thus, even though the brain likely contributes to the symptoms of ADHD, a specific causal link and clear method of biological assessment have yet to be found.

The Gift of ADHD: How to Transform Your Child's Problems into Strengths

More About this Book

The Gift of ADHD: How to Transform Your Child's Problems into Strengths

As a parent, you already know that your child has many gifts. What you may not know is that attention-deficit hyperactivity disorder (ADHD) related symptoms—the very qualities that lead him or her...
Dr. Douglas E. Severance, MD
Family Practitioner

The cause of attention deficit hyperactivity disorder (ADHD) is unknown. It seems as if certain changes in the brain are connected to ADHD. For instance, some people with ADHD have less activity in the part of the brain that manages attention. Also, ADHD appears to have a genetic component, and children who are exposed to toxins early in life, particularly lead, may be at higher risk for ADHD. In addition, smoking and drinking during pregnancy may be linked to ADHD in children.

One of the first questions a parent will ask me is “What did I do wrong? Did I cause this?” There is no evidence that ADHD is caused by lapses in child rearing, reactions to vaccines, or giving in to countless requests for sugar-loaded cookies. I tell parents to forget their inner blame game and focus on finding the best possible way to help their child. Let researchers try to discover the cause for ADHD. And they’re trying hard. Scientists believe genetic and environmental factors may play a role, and studies show that many children with ADHD have a close relative who also has the disorder. Experts also know that kids with ADHD have chemical changes in their brain and that certain areas of the brain are about 5 to 10 percent smaller in size and activity than normal.

Other studies about the cause of ADHD point to links with smoking during pregnancy, premature delivery, very low birth weight, and injuries to the brain at birth. Some research suggests a link between excessive early TV watching and attention issues. (That’s one of the reasons the AAP says that children under two should not have any screen time, that means no computers, TV, DVDs, or video games, and that kids two and older should watch no more than one to two hours a day of nonviolent, quality TV.)

From The Smart Parent's Guide: Getting Your Kids Through Checkups, Illnesses, and Accidents by Jennifer Trachtenberg.

The Smart Parent's Guide: Getting Your Kids Through Checkups, Illnesses, and Accidents

More About this Book

The Smart Parent's Guide: Getting Your Kids Through Checkups, Illnesses, and Accidents

What to Do When You Don't Know What to Do! "Moms and dads need expert guidelines, especially when it comes to their kids' health. This book reveals the inside strategies I use myself-I'm a parent, too!-to avoid critical, common blunders where it matters most: in the ER, pediatrics ward, all-night pharmacy, exam room, or any other medical hot spot for kids. These tips could save your child's life one day. Even tomorrow." -Dr. Jen Making health care decisions for your child can be overwhelming in this age of instant information. It's easy to feel like you know next to nothing or way too much. Either way, you may resort to guessing instead of making smart choices. That's why the nation's leading health care oversight group, The Joint Commission, joined forces with Dr. Jennifer Trachtenberg on this book: to help you make the right decisions, whether you're dealing with a checkup or a full-blown crisis. The Smart Parent's Guide will give you the information you need to manage the pediatric health care system. Dr. Jen understands the questions parents face—as a mom, she's faced them herself. She walks you through everything: from how to choose the best ER for kids (not adults) to when to give a kid medicine (or not to) to how pediatricians care for their own children (prepare to be surprised). Her goal is your goal: to protect the health of your children. There simply is nothing more important.

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Important: This content reflects information from various individuals and organizations and may offer alternative or opposing points of view. It should not be used for medical advice, diagnosis or treatment. As always, you should consult with your healthcare provider about your specific health needs.