Child Development

What Causes ADHD in Kids?

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Attention deficit disorder (ADHD), is a common neurodevelopmental disorder that’s usually first diagnosed in childhood and oftentimes lasts into adulthood. Children who have ADHD may have trouble focusing, controlling their behaviors, and being hyperactive.

While the causes and risk factors of ADHD are still being researched, current studies find that genetics can play a role in developing ADHD. In this article, I’ll outline the signs and symptoms, and the causes of ADHD. I’ll also go over the risk factors, and what does not cause ADHD. 

Signs and Symptoms

It is quite normal for children to have trouble focusing and behaving at one time or another. However, when children have ADHD, they do not just grow out of these behaviors. The symptoms continue, can be severe, and can cause difficulty at school, at home, or with friends.

A child with ADHD might:

  • Daydream a lot
  • Forget or lose things a lot
  • Squirm or fidget
  • Talk too much
  • Make careless mistakes or take unnecessary risks
  • Have a hard time resisting temptation
  • Have trouble taking turns
  • Have difficulty getting along with others

However, these signs are not one size fits all. There are three presentations of ADHD. Depending on the presentation, ADHD symptoms may vary in children:

  1. Predominantly Inattentive Presentation: It is hard for the child to organize or finish a task, to pay attention to details, or follow instructions or conversations. They are easily distracted or forget details of daily routines.
  2. Predominantly Hyperactive-Impulsive Presentation: The child fidgets and talks a lot. It is hard to sit still for long (e.g., for a meal or while doing homework). Smaller children may run, jump or climb constantly. They feel restless and have trouble with impulsivity. Someone who is impulsive may interrupt others a lot, grab things from people, or speak at inappropriate times. It is hard for the person to wait their turn or listen to directions. A child with impulsiveness may have more accidents and injuries than others.
  3. Combined Presentation: Symptoms of the above two types are equally present in the child.

Causes and Risk Factors of ADHD

The exact cause of ADHD is not yet clear, and researchers continue to look into this. However, there are factors that might put a person at greater risk for developing ADHD, such as genetics, illness and injury, premature birth, environmental toxins, and exposure to cigarettes or alcohol in the womb.


ADHD is primarily a hereditary disorder. In fact, it’s estimated that the percent of genetic contribution to ADHD is nearly 70%. However, it’s important to know that just because you have ADHD, does not guarantee your child will inherit it. Genetics is not the only dependent on someone developing ADHD; there’s also the genetic combination of the mother and father and environmental factors.

ADHD genes can be inherited without being activated. A research study showed that one-third of fathers with ADHD had children that also developed ADHD. In addition to this, the presentation type is not inherited, and a child can develop a different presentation than their parent. While ADHD is more commonly diagnosed in males than females, ADHD is a not sex-linked condition and can be diagnosed in either gender.

Illness and injuries

Research supports that illnesses such as meningitis or encephalitis can possibly result in problems with learning and attention. A study in JAMA Pediatrics has found that children who have experienced traumatic brain injuries are at a greater risk for developing ADHD. The risk is increased for up to 10 years after sustaining the injury.

Premature birth

Children born preterm (before 33 weeks of gestation) are at a two to three-fold risk of being diagnosed with ADHD compared to those born at term. It’s believed that being born early can injure the brain, disrupting the normal sequence of brain development processes.

Exposure to environmental toxins

If exposed to environmental toxins, such as lead while in utero, a child has a greater chance of developing ADHD. Exposure to other toxins, such as pesticides (also known as organophosphates), can also lead to an increased risk of developing ADHD. 

Mother’s lifestyle during pregnancy

A mother’s lifestyle can impact the risk of a child developing ADHD later on. Nutrition, smoking, and alcohol use can increase the risk of a child developing ADHD. 


A high-fat, high-sugar diet during pregnancy may be linked to symptoms of ADHD in children who show symptoms early in life.


It’s been found that mothers who smoked during pregnancy had a 60 percent higher risk of having a child with ADHD compared to mothers who didn’t smoke.  Additionally, mothers who smoked fewer than 10 cigarettes per day had a 54 percent higher risk of having a child who developed ADHD than nonsmoking mothers. For mothers who were heavier smokers, the risk was 75 percent higher than for nonsmokers.

Alcohol use

Consuming alcohol during pregnancy can also increase the risk if a child developing ADHD. Consuming four or more drinks or regular low to moderate alcohol use was associated with a significant increase in the chances that a child would later have ADHD.

What Does Not Cause ADHD

It’s common to have misconceptions about certain disorders and conditions. However, there is no conclusive evidence that supports that ADHD is caused by:

Too much sugar

Research studies show that sugar does not cause hyperactivity, or aggravate most people’s ADHD symptoms. While sugar and ADHD can cause excessive energy and should be consumed in moderation, it does not effect the cognitive performance of children.


Multiple studies have confirmed that vaccines do not cause ADHD. Most concerns surrounding vaccines causing ADHD is related to thimerosal, a mercury-containing preservative. This was in several vaccines commonly given during the first few years of life.

However, the type of mercury in vaccines is called thimerosal and is made of ethyl mercury. Ethyl mercury is less likely to accumulate and cause negative effects compared to methyl mercury (the type of mercury in fish) because it is eliminated from the body much quicker.

Poor parenting

Many people believe that poor parenting causes ADHD. However, ADHD is a brain disorder and bad parenting cannot cause it.


The causes of ADHD are still being researched. However, studies have shown a prominent link between genetics and developing ADHD. It’s important to also recognize that there are myths about the causes of ADHD, such as too much sugar, vaccines, or poor parenting.