When a child is newly diagnosed with ADHD, parents often want to know what causes the condition. Was it something in the environment when the child was very young that prompted the development of these symptoms? In some families without a medical history of ADHD there may be questions of what the child might have experienced or what treatment he received that could be the root cause of ADHD.

These questions are natural to ask and they are ones that researchers have been pursuing for about 50 years. Research has become clearer that ADHD is genetic, runs in families, and for a smaller number of people could be related to prenatal exposure to alcohol or tobacco smoke. In a few cases, researchers are exploring the possibility of an environmental pollutant.

What researchers are sure of, though, is that ADHD is not caused by vaccines given to prevent childhood illness.

A fraudulent study published in 1999 claimed the measles-mumps-rubella (MMR) vaccine was the cause of autism and autism spectrum disorder. This caused two very important trends–the first prompting thousands of parents to forgo or delay vaccines for their children out of the fear of the child developing autism. The second was a flurry of studies to confirm or refute the study’s assertion. In the end, 12 years after the original study was published, the Lancet retracted the published study and the study author’s license to practice medicine was revoked by the United Kingdom’s General Medical Council.

Researchers across the globe conducted numerous studies on the MMR vaccine and other vaccines related to developmental disabilities. With the exception of situations where the child had a pre-existing condition, researchers found no evidence that vaccines caused autism.

But in the internet age, where opinion is weighed equally to fact, the myth persists. Because many people associate ASD with ADHD, the idea has expanded to include vaccines having a relationship to ADHD or ADHD-like symptoms.

Many websites and blogs state that vaccines are somehow the root cause of ADHD, either by causing inflammation in the body or otherwise creating damage to certain areas of the brain. There are popular websites hosted by some with medical degrees and others who claim to be experts in natural health that continue to promote this claim. Some alternative health practitioners also claim vaccines or ingredients in vaccines cause ADHD and share this belief with their clients.

The American Academy of Pediatrics assembled a listing of studies that examined vaccines and ASD and related disorders. Vaccine Safety: Examine the Evidence lists 43 medical studies that conclude there is not a relationship between vaccines and ASD or related cognitive conditions, such as ADHD.

Vaccines are not associated with autism: An evidence-based meta-analysis of case-control and cohort studies reviewed five cohort studies for a total of 1,256,407 children and concluded “vaccinations are not associated with the development of autism or autism spectrum disorder. Furthermore, the components of the vaccines (thimerosal or mercury) or multiple vaccines (MMR) are not associated with the development of autism or autism spectrum disorder.”

For ADHD specifically, the Children’s Hospital of Philadelphia lists the results of three studies to show that ADHD is not caused by vaccines. Those studies are:

Together, these studies state there is no association between the timing of vaccines or the ingredients in them to the development of ADHD.

“Parents can be reassured that vaccines do not cause ADD/ADHD or related conditions,” according to the Children’s Hospital.

Max Wiznitzer, MD, is familiar with the research on suspected links between ADHD and vaccines. Dr. Wiznitzer is a pediatric neurologist at Rainbow Babies & Children’s Hospital in Cleveland, Ohio. He is an associate professor of pediatrics, neurology and international health at Case Western Reserve University and is the co-chair of CHADD’s Professional Advisory Board.

He says the research shows there is no connection between vaccines and ADHD.

“The diseases for which vaccines are given do not cause ADHD,” Dr. Wiznitzer says. “If the disease does not, then the vaccine, which is made from the bacteria or viruses, should not since they have the same ‘active’ components.”

What about the other compounds in vaccines, called adjuvants, which are intended to increase the body’s immune response and create a stronger immune reaction to protect the person from the disease? Some people have expressed concern about those compounds related to ADHD and other conditions.

“Research has not shown an association between vaccine adjuvants, such as thimerosal, and symptoms of ADHD,” Dr. Wiznitzer says. “In addition, removing thimerosal from vaccines was not associated with a decrease in the prevalence of ADHD. Research has not shown an association between aluminum or mercury (both parts of vaccine adjuvants) in the environment and ADHD.”

And the number of vaccines given at one time or in one shot? Again, some people have asked if the number of vaccines could play a role in the development of ADHD.

“Research has not shown an association between number of vaccines given at one time and ADHD symptoms,” he says.

Frequently, popular belief combines ADHD and ASD by claiming they share the same cause because their surface symptoms often share similarities even though they are two distinct conditions. The false belief that vaccines are related to the cause of autism has moved into the world of ADHD, again claiming vaccines as the cause of ADHD.

ADHD is not caused by vaccines, Dr. Wiznitzer says. The ingredients, the inert bacteria or virus, and the adjuvants have no impact on the development of ADHD.

Research has shown ADHD is an inherited condition, and when it is not inherited may be related to prenatal exposure to specific substance—none of which are vaccines. There is no evidence that ADHD is caused by a single vaccine or a combination of vaccines.

There is a great deal of evidence that vaccines have saved lives and contribute to a healthier population. Following the recommended vaccine schedule for a healthy child is one of the best things a parent can do to protect their children’s health and future.

For more information on vaccines, vaccine safety, and your child’s health visit: