Little is known about what causes ADHD. Some signs point to the brain’s messengers – neurotransmitters – playing a key role.

Attention deficit hyperactivity disorder (ADHD) is a common condition that can be diagnosed in children and adults. Its classic symptoms of inattention and hyperactivity or impulsivity can affect how you perform at school or work.

It can also cause problems with how you relate to co-workers, family, friends, and loved ones.

Over the years, the numbers of ADHD diagnoses has been on the rise.

But why?

There are many factors that contribute to the development of this condition. Low levels of neurotransmitters is but one of those factors believed to play a role in ADHD.

Still, researchers are looking into the exact causes and factors that may contribute to the development of this condition.

Neurotransmitters are chemical messengers in your brain that allow your brain cells and other parts of your body to communicate. They are created in your nerve cells, specifically in the presynaptic terminals, and are released at certain times to pass information on to your other nerve cells.

Some of the most well-known neurotransmitters are:

  • dopamine – releases in response to pleasure and helps reinforce and motivate you to repeat the pleasurable action, like eating your favorite meal or listening to your favorite album
  • serotonin – helps regulate and control many of your body’s automatic functions such as sleeping, digestion, and blood-clotting, as well as helping stabilize your mood and emotions
  • epinephrine – also known as adrenaline, this neurotransmitter can increase your heart rate and blood sugar levels in response to stress or danger, which triggers your body’s fight, flight, or freeze response
  • norepinephrine – works similarly to epinephrine and causes your blood vessels to narrow, which produces a temporary increase in blood pressure

Your brain is full of different neurotransmitters, and each one plays a special role in how your brain communicates with other parts of your body.

“At the tip of each neuron is a small gap, which is called a synapse,” explains Sanam Hafeez, PhD, licensed neuropsychologist and founder of Comprehensive Consultation Psychological Services, P.C, in New York. “For neurotransmitters to send messages to each other, the signal needs to jump across the synapse from one neuron to the next.”

This process, Hafeez says, is called neurotransmission.

“What makes this process slightly more complicated is that a receptor on the end of the receiving neuron can only bind to a specific neurotransmitter,” Hafeez continues. “The neurotransmitter acts as the key, and the receptor acts as a lock. These two need to fit together in order for the signal to be passed on.”

This process can be complicated if the brain is creating too much or too little of a neurotransmitter or if there’s a dysfunction in the amount of that neurotransmitter being collected by your nerve cells.

While there’s no known specific cause for ADHD, varying dopamine levels, norepinephrine, and serotonin in the brain can contribute to the severity of its symptoms.

For example, because dopamine helps you focus and rewards your brain for completing tasks, having lower dopamine levels in the brain means a person might have trouble maintaining focus on a task or seeing it through to the end.

“The research shows that those with ADHD have more dopamine transporter proteins, which work to remove dopamine from the brain,” explains Hafeez. “If there are too many dopamine transporters in someone’s brain, too much dopamine is being removed too quickly.”

There is still so much to learn about ADHD, and any one of these factors isn’t believed to be solely responsible for causing it.

“Just because someone has too many dopamine transporters does not necessarily mean they have ADHD,” says Hafeez.

Certain lifestyle changes – such as adjusting what food you eat and exercising more – can change the level of neurotransmitters in your brain and the speed they are absorbed into your nerve cells.

Diets lacking nutrients can lower levels of serotonin.

Some research suggests that tryptophan-rich foods – such as turkey, cheese, and peanuts – might increase serotonin. Pairing these foods with carbohydrates might even boost serotonin production. For example, eating a turkey and cheese sandwich or pretzels with peanut butter might increase your serotonin levels.

Physical activity releases dopamine and serotonin, which can help increase the levels of these neurotransmitters in the brain.

Some ADHD medications, Hafeez says, can help change the level of neurotransmitters, too.

“[ADHD medication slows] the speed that dopamine is absorbed,” explains Hafeez. “Since people with ADHD are thought to have a higher number of dopamine transporters that remove the dopamine too quickly from the brain, the [medication] is acting against this effect by allowing more dopamine to stay present in the brain for a longer period of time.”

There are two common types of medications for ADHD: stimulants and non-stimulants. Both change the levels of neurotransmitters.

Stimulants focus on spurring neurotransmitter production so that a higher amount is created at a faster rate. As a result, this increase in neurotransmitters allows a higher level to be present in the brain and can help counteract the problem of over-absorption that some people may have.

Nonstimulants have a similar outcome. They slow down and inhibit how fast neurotransmitters are absorbed, which allows for a higher level of neurotransmitters available because it’s not being used at such a high rate.

However, since ADHD is experienced in different ways from person to person, changing the levels of neurotransmitters might not be helpful for everyone with ADHD.

Though low levels of neurotransmitters can affect the body, there’s no strong evidence linking them and ADHD.

Changing the levels of neurotransmitters in the brain through medication has proven to be helpful for some people with ADHD, but it might not necessarily work for everyone.

If you or someone you know has ADHD and want to know more about whether lower levels of neurotransmitters contribute to your symptoms, consider talking with your family physician or a mental health professional specializing in ADHD.