Causes of Attention-Deficit/Hyperactivity Disorder

As more research is being done on Attention-Deficit/Hyperactivity Disorder (ADHD), we are able to get a deeper understanding of what causes the condition. Here are seven known causes 

Genetics

ADHD is primarily a hereditary disorder. It is estimated that 80% of individuals diagnosed with ADHD have inherited the condition.

Studies on twins and adopted children have been helpful in determining what role the environment plays and what role genes play.

Studies on families have also added to our knowledge about the genetic factors of ADHD.  

Patricia Quinn, MD  is a developmental pediatrician with more than 30 years of experience working with children and families with ADHD and learning disabilities. She says an in-depth family history is often very revealing. Family trees can be created and can help identify those family members who display symptoms of ADHD, including those adults who were never diagnosed. Despite the lack of a formal diagnosis, history may reveal that these adults feel they could never settle down, changed jobs frequently, have chronic problems completing projects, organizing their life, etc.

If you inherit ADHD from a parent, their ADHD presentation (or subtype) whether Inattentive, Hyperactive-Impulsive or combined, will not influence the ADHD presentation you have.

Lead Exposure

Exposure to lead (even low levels) during pregnancy or as a child can result in hyperactivity and inattention.

Lead can be found in surprising places, such as in the paint of homes built before 1978 or in gasoline

Exposure to Substances in Utero

Being exposed to the substance during pregnancy can increase the risk of ADHD.

Maternal Cigarette Smoking 

One study found a significant relationship between the number of cigarettes smoked during pregnancy and the risk of ADHD to the child.

The more cigarettes smoked, the higher the chance of ADHD. 

Maternal Alcohol Use

One study found mothers who abused alcohol while pregnant were twice as likely to have a child with ADHD, and mother that were dependent on alcohol in pregnancy were 3 times as likely to have a child with ADHD.

A Premature Birth

Being born prematurely and/or with low weight increases the chance of developing ADHD.

Obstetrical Complications

Pregnancy problems such as eclampsia or a long labor is another factor.

Certain Illnesses 

Illnesses such as meningitis or encephalitis can result in learning and attention problems.

Head Trauma and Brain Injury

A small percentage of the population will manifest ADHD symptoms as a result of brain damage, such as an early brain injury, trauma or another impediment to normal brain development. 

What Does Not Cause ADHD

As more research is carried out, not only are we learning what causes ADHD we are also learning what does not cause ADHD.   

Here Are 5 Things That Do Not Cause ADHD

1) Watching  TV 

2) Diet, including too much sugar

3) Hormone disorders (such as low thyroid)

4) Poor parenting

5) Playing video and computer games

Here are some other interesting facts about ADHD that Dr. Quinn shared with me during our interview.

ADHD is Not Sex Linked

ADHD is not a sex-linked condition. In other words, ADHD does not occur only in males and is thus not passed down only from a father to the children. So often people think -- “It’s only fathers who can have ADHD, and if the dad doesn’t have ADHD then the child can’t possibly have it.” This is inaccurate. It is important to understand that as many mothers as fathers may have ADHD.

There Is Not One Specific Gene

To date, several gene candidates have been found in families who demonstrate ADHD; however, scientists feel that it is not one particular gene but the interaction of several of these genes and the environment that cause ADHD symptoms to manifest.

Chances of Occurrence

If one child in the family is diagnosed with ADHD, there is a 60% chance that each additional child will also have it. That is not to say 60% of your kids will have ADHD if one does, rather this means that for every additional child you have there is a 60% chance that that child will also have ADHD.

Source:

Banerjee, T. D., Middleton, F., & Faraone, S.V (2007). Environmental Risk Factors For Attention-Deficit Hyperactivity Disorder. Acta Paediatrica, 96, 1269-1274

Faraone, S. V., Biederman, J., Spencer, T., Wilens, T., Seidman, L. J., Mick, E., et al  (2000) Attention-Deficit/Hyperactivity Disorder in Adults: An Overview. Biological Psychiatry, 48,9-20.

Milberger, S., Biederman, J., Faraone, S. V., Chen, L., & Jones, J. (1996) Is Maternal Smoking During Pregnancy a Risk Factor for Attention Deficit Hyperactivity Disorder in Children?  American Journal of Psychiatry, 153,1138-1142 

Patricia Quinn, MD. Phone interview/email correspondence. January 5 and 27, 2009.