ADHD Causes : What Causes ADHD ?

There are many causes of ADHD, and each of them has a biological basis. Genetics play a role, as does neurology. There are at least four areas of the brain that are associated with ADHD or attentional difficulties, maybe more. Some people who have been diagnosed with ADHD actually "acquired" it through a head injury (either before or after birth) and have been mis-diagnosed. ADHD is not caused by watching too much TV, poor parenting, or a lack of love from the family.

The most recent models that attempt to describe what is happening in the brains of people with Attention Deficit Hyperactivity Disorder suggest that several areas of the brain may be affected by the disorder. They include the frontal lobes, the inhibitory mechanisms of the cortex, the limbic system, and the reticular activating system. Each of these areas of the brain is associated with various functions.

Brain imaging gives new insight into underlying cause of ADHD

Brain imaging gives new insight into underlying cause of ADHD

There are several areas of the brain potentially impacted, and there are several possible "types" of ADHD. Daniel Amen, a medical doctor using SPECT scans as identified six different types of ADHD, each with its own set of problems, and each different from the other "types."

In our practice we used five different "types" of ADHD, identifying each "type" with a character from the Winnie the Pooh stories (Pooh is inattentive, Tigger is hyperactive, Eeyore is depressive, and so on). We discuss in greater detail in the Different Types of ADHD section.

Certain areas of the ADHD brain may be smaller than those without ADHD (by as much as 10%) and they may be less active, and less developed too. And these differences continue even as the person grows and matures with age. The typical ADHD individual is two years behind his peers in the maturation of the brain and nervous system.

The frontal lobes help us to pay attention to tasks, focus concentration, make good decisions, plan ahead, learn and remember what we have learned, and behave appropriately for the situation. The frontal lobes help us to be organized, filter out unimportant distractions, and help with "working memory." These are called our "executive functions."

ADHD impairs and disrupts these "executive functions" in several ways.

The inhibitory mechanisms of the cortex keep us from being hyperactive, from saying things out of turn, and from getting mad at inappropriate times, for examples. They help us to "inhibit" our behaviors and emotions.

It has been said that 70% of the brain is there to inhibit the other 30%.

The limbic system is the base of our emotions and our highly vigilant look-out tower. If over-activated, a person might have wide mood swings, or quick temper outbursts. He might also be "over-aroused," quick to startle, touching everything around him, hyper-vigilant.

A normally functioning limbic system would provide for normal emotional changes, normal levels of energy, normal sleep routines, and normal levels of coping with stress. A dysfunctional limbic system results in problems with those areas.

The Attention Deficit Hyperactivity Disorder might affect one, two, or all three of these areas, resulting in several different "styles" or "profiles" of children (and adults) with ADD ADHD.

These regions of the brain, and the systems that connect them, are all disrupted by ADHD in some way. And as a result ADHD causes problems with inhibition of behaviors and emotions, people are easily distracted, working memory is impaired, people are less aware of time passing or what time it is, and are less able to plan for the future. Those with ADHD are less motivated to complete tasks on time, or at all, and are typically not very good at problem solving or planning ahead. ADHD impairs the way that people perform at work, at school, at home, and in social settings.

Neurology of Attention Deficit Hyperactivity Disorder : What Causes ADHD ?

Brain imaging studies show that the brains of those with ADHD are different from those without ADHD in terms of size, activity, and development. Certain regions of the ADHD brain can be as much as 10% smaller than those without ADHD. And areas such as the frontal lobes, cerebellum, and anterior cingulate, can be very under-active compared to normal. These areas can also be as much as two to three years behind in development compared to normal. These differences will remain through the life of a person with ADHD.

ADHD impacts various systems of the brain, particularly systems involved with "executive functions", "inhibition", and "working memory". Most of these involve the activity of the frontal lobes, and the interaction of the frontal lobes with other structures of the brain acting as a "system". But since the frontal lobes are smaller, less active, and behind in development, each of these systems is impacted to some degree. As other areas of the brain are also affected, the look or type of ADHD is different.

Many studies are looking at how the ADHD brain matures in children and teens, and how it matures differently than someone without ADHD. We have discussed this at the ADHD Information Library considering both brain development in children, and in teenagers. One recent study funded by the National Institutes of Health and led by Dr. Philip Shaw considered this important issue. Their research is published in Biological Psychiatry.

It is estimated that about 9% of all children have ADHD. Of children referred to mental health professionals, more are referred for ADHD than for any other condition. But ADHD is also one of the most treatable of all psychiatric disorders, with several effective options ranging from medications to alternative therapies, psycho-social treatments, and educational interventions. Those with ADHD can have problems in many of the areas of their life, including home, school, work, and in relationships. ADHD is a chronic and unrelenting problem. Though it will change in form through the years, it will persist into adulthood and impact all relationships including marriages, parenting, and work performance. While there are different types of ADHD, depending on the different areas of the brain that are impacted most, there are commonalities that everyone with ADHD will contend with. No matter the types of ADHD, there will be at least some degree of Inattention; some degree of frontal lobe involvement; some degree of working memory deficits and executive function impairment; some problems at school; and some degree of delayed brain development.

Here's a good resource developed by some researchers at Harvard to help improve working memory. Its a computer based program to improve working memory in children and teenagers.

ADHD brain maturation delay
(Video, MP4 File)

In this particular study 230 kids with ADHD and 230 kids seemingly without ADHD underwent a series of brain scans to measure both the thickness of the brain cortex and the cortical surface area. The subjects without the ADHD were used as a control group. The children were first scanned at about the age of 10, and then again about every two years ending by age 17. Using the latest brain imaging tools the research team mapped the surface area development across the brain. Their study was consistent with other recent studies, that the brain development in the frontal lobes is delayed in those with ADHD. The brain maturity or development, in terms of size and surface area, is about two years behind the development in non-ADHD children and teenagers.

Impulsivity in the ADHD Brain

New Research Offers Insight Into Cause Of Impulsivity in ADHD

We have often felt sorry for those impulsive children who blurt out the first thing that comes to their mind when asked a question, especially if they are about to get into trouble. As most parents know, that first thing that comes out as the answer is usually a lie. And then the child has to spend the rest of the hour covering up the lie, that both he and his parents know is a lie. This is a classic scene of a child with ADHD getting into trouble because of his impulsivity.

As a remedy, we encourage parents to warn the child that they are about to be asked a very serious question, and that their honesty is absolutely required. And that the child is not to answer the question for 30 seconds after being asked, so that they can clearly think about what they want to answer and get it right the first time. This works.

But it is not what this article is about...

Impulsivity in ADHD

Impulsivity in ADHD is seen in two ways: (1) either doing or saying something without thinking first; or (2) not saying “no” to yourself, inhibiting yourself, when you ought to do so.

It seems that a person with impulsivity as a part of their ADHD has a normal ability to say “Go” at the neurological level, but their ability to say “No” or “Stop” comes just a fraction of a second slower. As a result, things are often done, or said, without much self-control practiced.

Vanderbilt Research on ADHD

There is some very interesting new research out of Vanderbilt University’s Center for Integrative and Cognitive Neuroscience that helps to explain impulsivity in ADHD. From their press release, here are the basics of the study:

"We think of people who are impulsive as acting too quickly," said Gordon Logan, one of the researchers. "Kids with ADHD are actually slower on the 'go' task than the control kids. It's not that they go too quickly; they stop too slowly."

"The research provides new insights into how the brain controls movements, which helps explain the impulsivity of people with attention deficit and hyperactivity disorder," according to study co-author Jeffrey Schall, E. Bronson Professor of Neuroscience. "It also shows how mathematical models can be used to discover how the brain produces thought and action."

Vanderbilt psychologists Leanne Boucher, Thomas Palmeri, Gordon Logan and Schall published the findings in the April issue of Psychological Review.

The new paper uses physiological data collected in Schall's laboratory to show how a theoretical model Logan developed more than 20 years ago is implemented by the brain.

"I developed the race model to explain behavior on a task called the stop signal task with a friend of mine, William Cowan, who is a theoretical physicist, in the 1980s," Logan, Centennial Professor of Psychology, said. Stop signal tasks measure an individual's ability to stop a planned action, like pressing a key on a keyboard or looking at a target, in response to a signal. "Our race model proposed that two independent processes were underway, one telling us to 'go' and one telling us to 'stop' in response to the stop signal.

"Applying the model to children's behavior revealed that stop signal task times are significantly longer in children with attention deficit and hyperactivity disorders than in other children," he said.

In this model, "go" and "stop" processes independently race one another - whichever one crosses the finish line first determines whether a movement is made or not. Though the model accurately explains behavior, it left neuroscientists scratching their heads. Their work found that 'go' and 'stop' processes are produced through a complex network of interacting neurons. If so, then how could 'go' and 'stop' be acting independently as required by the race model?

"The model proposes that there are two processes happening in our brain, one making us 'go' and another making us 'stop'," Boucher, a postdoctoral fellow, said. "However, as neurophysiologists, we know these processes are intricately linked, not independent.”

The findings are some of the first to bridge cognitive research and neurophysiology - making the connection between the mind and the brain.

For more information about this study visit the Vanderbilt website.

Press Release by Melanie Moran

Attention Deficit Disorder and the Reticular Activating System

What causes these various systems of the brain to get out of balance with Attention Deficit Hyperactivity Disorder individuals? Why would these systems become under aroused or over aroused? Is there one central system that controls or regulates these other systems?

The answer may be found with the Reticular Activating System.

The Attention Center of the ADHD Brain

The Reticular Activating System is the attention center in the brain. It is the key to "turning on your brain," and also seems to be the center of motivation.

The Reticular Activating System is connected at its base to the spinal cord where it receives information projected directly from the ascending sensory tracts. The brainstem reticular formation runs all the way up to the mid-brain. As a result, the Reticular Activating System is a very complex collection of neurons that serve as a point of convergence for signals from the external world and from interior environment.

In other words, it is the part of your brain where the world outside of you, and your thoughts and feelings from "inside" of you, meet.

This Reticular Activating System is very capable of generating dynamic effects on the activity of the cortex, including the frontal lobes, and the motor activity centers of the brain.

The Reticular Activating System and Learning

The Reticular Activating System plays a significant role in determining whether a person can learn and remember things well or not, on whether or not a person is impulsive or self-controlled, on whether or not a person has high or low motor activity levels, and on whether or not a person is highly motivated or bored easily.

The RAS is the center of balance for the other systems involved in learning, self-control or inhibition, and motivation. ADD ADHD Reticular Activating System Neurology

When functioning normally, it provides the neural connections that are needed for the processing and learning of information, and the ability to pay attention to the correct task.

If the Reticular Activating System doesn't excite the neurons of the cortex as much as it ought to, then we see the results of an under-aroused cortex, such as difficulty learning, poor memory, little self-control, and so on. In fact, if the Reticular Activating System failed to activate the cortex at all one would see a lack of consciousness or even coma.

How the Body Works : The RAS Pathway

How the Body Works The RAS Pathway Information entering the brain along the sensory nerve pathway passes to the sensory cortex. However, nerve branches from the pathway first send impulses to the ascending reticular-activating system or RAS, which st...

What would happen if the Reticular Activating System was too excited, and aroused the cortex or other systems of the brain too much?

Then we would see individuals with excessive startle responses, hyper-vigilance, touching everything, talking too much, restless, and hyperactive.

So the Reticular Activating System must be activated to normal levels for the rest of the brain to function as it should.

What factors could cause the Reticular Activating System to be either over-activated or under-activated? According to Harvard Medical School, current research strongly suggests that Attention Deficit Disorder – ADHD is caused in part by a deficiency of Norepinephrine in the ascending reticular activating system.

It is thought that the stimulant medications, such as Ritalin, increase the levels of Norepinephrine in that part of the brain, as well as probably increasing dopamine levels in the frontal lobes.

More Neural Connections Needed

However, it is not just activation levels of the Reticular Activating System that are a problem with Attention Deficit individuals. It seems that the same problems that cause the Reticular Activating System to be under or over aroused also restricts the development of neural connections and the required neural density needed to process incoming information. In other words, these are issues with the number of brain cells, the size of the brain cells, and the number of connections between brain cells. It is not uncommon for one brain cell to have as many as 5,000 connections with other brain cells.

Picture the incoming information to be processed and learned as the volume of water coming out of your shower head. And picture the brain's ability to process this information as the drain and the drain pipe in the shower floor. If the pipe is clogged up, your shower will have problems draining. If the contractor originally installed a drain pipe that is too small, again your shower will have problems draining. In either case, you will either have to reduce the amount of water coming out of the shower head, or you will have to let the shower back up and wait a while for the water to finally drain out. Here’s the connection…

If the brain does not have enough neural connections, or lacks the neural density to process the incoming information, then it will be like a pipe that is too small to handle a large volume of water. It will take in some, but the rest will be stopped and won't go down the pipe rapidly. Learning will take place, but the time that it takes to process the information will be slowed significantly.

The impact of this with an Attention Deficit Hyperactivity Disorder child is best seen when the child is given a timed test, even with material that the child understands pretty well.

The "timed" aspect of the test requires that the child have a “larger drain pipe,” as it were, to quickly process the problems on the test and recall the answer. However, with ADHD the “pipe” is often too small, and the results of the timed test will probably be very poor.

However, take away the timed element on the same test, and “allow the water to drain a the slower rate,” and the child will probably do well on the test.

So the ADHD child, or adult, needs a greater degree of neural density, and a larger number of neural connections to process information faster and more efficiently.

Now, please do not think that this information to be processed is only what takes place in the classroom. The information to be processed includes information from the outside world, including the touch of the clothes on his skin, the buzz of the lights overhead, the sound of the kids playing outside, and the new information that the teacher is lecturing on at the front of the classroom.

It also includes the information from inside the head, the thoughts and feelings of the ADHD person.

All of that must be sorted out and filtered, so that only the important information is paid attention to, and the unimportant information is ignored. Without proper filtering by the Reticular Activating System, the individual will be distracted by "noise," both from outside of him as well as from inside of him.

Do Astrocytes Play a Role in Brain Performance?

Our brains are tremendously complex – in may respects as vast as the universe. The brain is organized into different regions that each seems to have a particular function of expertise. The brain itself is composed of various types of brain cells, fatty acids, fluids, and neurotransmitters. We have heard about neurons like the “grey matter” of the brain, which are found in the more interior regions of the brain, and perhaps about “white matter” which separates the grey matter into various regions, and so on.

But one of the least discussed type of brain cell are the astroglia. These Astrocyte cells have usually been described as simply being the “glue” that holds the brain together, and they provide nutritional support to parts of the nervous system. But new research is discovering new importance to this type of brain cell that might actually make a difference in how we understand ADHD in the human brain.

A study recently published in Science Signaling from a research team at University of Rochester Medical Center reports that these astrocytes are much more important that we had previously thought. The team reports that these cells are very important in slowing down or stopping various brain activities, or reducing their intensity. They also play a role in determining when various neurons will “fire” and when they won’t. This understanding goes far beyond previous descriptions of the astrocytes as simple “nurse maids” to neurons, working to keep them healthy and happy.

For the brain to function optimally many factors have to be operating in sync with each other. There has to be an optimal balance of sodium and potassium, and a proper balance of calcium and magnesium, for the cells to work well, and these astrocytes are active in maintaining this balance by getting rid of any excesses of these minerals. But they can also control actual neuronal activity by controlling potassium levels in the area around them as they live among the neurons in the cortex.

By the way, its good to help them out by finding good sources of these minerals in your daily diet. And in a pinch here are some tips:

• You can boil cubes of potatoes in a pot for a couple of hours. Then throw the potatoes away and drink the juice in the pot. It will be high in potassium;
• If you are taking potassium supplements, and you get real hot and sweat a lot, the sodium-potassium balance may be severely impacted. My wife had a seizure once due to this. The solution, eat a potato chip or corn chip with salt every so often;
• If you take calcium supplements, make sure that there is a balance of magnesium with the supplement.

Part of what has been learned in studying astrocytes is the importance of gliotransmitters such as glutamic acids (also an important neurotransmitter) and ATP in the communication between neurons and astrocytes. This new research has also found that by the astrocytes controlling potassium levels around them, the control neuronal activity levels and reduce the “noise” or “static” among the neurons so that they are more efficient.

This may give new clues into future treatments for epilepsy, tic disorders, and ADHD.

Keywords: astrocytes, adhd, potassium, neurons