What Causes ADHD?

Face It — People with ADHD Are Wired Differently

The more we “see” the ADHD brain with neuroimaging, the more we understand how it works. Read this in-depth breakdown to learn about the latest discoveries and the most current research on the ADHD brain.

Cartoon lightbulbs representing the most current research on ADHD
Cartoon lightbulbs on light blue background

On a hot summer day in my new office, my client and I were shivering cold. “The air conditioning is hyperactive, maybe?”  I jokingly wondered as we pulled on sweaters. I turned the thermostat up to 76 degrees, then 80, but the cold air wouldn’t stop.

“Our HVAC system seems overactive,” I explained later to my husband. “Could it be too big for the office space?”

“It’s probably the thermostat, not the air-conditioner,” he said. His insight didn’t warm my office, but it made sense. It wasn’t a cooling-system problem, but a control-system problem. Punching temperature control buttons wasn’t helpful if the instructions weren’t getting to the air-conditioner.

A few days later, I met an office neighbor. When I told him about my problem, he proposed another theory: “Your thermostat doesn’t work. My thermostat controls your air conditioner. We aren’t really sure if it controls my offices. No matter how much I lower it, we’re always too hot.” A little more investigation revealed that his thermostat didn’t control my office, and that no one — not even the building’s owners — understood the wiring.

Understanding how ADHD brains are wired is critical for understanding how to explain and treat the disorder. For decades, we weren’t sure how ADHD brains worked, and this led to many misunderstandings about the syndrome. Many doctors, therapists, social workers, and coaches tried to teach children with attention deficit disorder (ADHD or ADD) to slow down using the self-control methods that neurotypical children use. They thought they were programming the right thermostat.

[Free Download: Secrets of the ADHD Brain]

“Take a deep breath and press the following buttons on your activity thermostat” makes sense if the wiring is standard, but not if the wires are connected differently, as they are in children and adults with ADHD. The most current research on brain imaging is starting to let us trace the wiring, so we can untangle the misconceptions that experts, as well as those with ADHD, have about the disorder and the brain. Our new understanding of the brain promises to change the way we treat ADHD.

The Brain Up Close

Researchers use structural imaging, which provides two- or three-dimensional pictures, to uncover the anatomy of the brain. Computed tomography (CT) scans and magnetic resonance imaging (MRI) are examples of structural imaging techniques. The images are used to measure the size and volume of the whole brain or specific areas within the brain.

To study brain functions, researchers use scans that show physiologic activity inside the brain. You’ve probably seen these studies covered in the press. The coverage usually includes statements like “X is the part of the brain that ‘lights up’ when people do Y.” Older functional scans — electroencephalography (EEG) and single-photon emission computed tomography (SPECT) — measure patterns of nerve activity or blood flow, respectively. Newer methods, such as positron emission tomography (PET), use radioactive tracers that can be seen in the brain.

Much of what we know about dopamine function in the brain results from the radioactive tracer raclopride, which is injected into the body and attaches to empty dopamine receptors. Raclopride binding is higher in the brains of children or adults with ADHD, so we “see” that their dopamine activity levels are low. Raclopride binding drops to normal levels an hour after stimulant medications are taken. This is why neuroscientists now say that stimulants normalize dopamine function in the brains of people with ADHD.

[Neuroimaging and ADHD: Findings, Limitations, and Promise]

Functional imaging gives information about activity in specific areas of subjects’ brains before and during task performance. Functional magnetic resonance imaging (fMRI) shows oxygen uptake in areas of high nerve activity, and magnetoencephalography (MEG) shows us nerve activity in detail. A promising variant of fMRI, called fMRI-DTI (for diffusion tensor imaging), measures the connection between different regions of the brain. Crosstalk — the ability of different regions of the brain to communicate with each other — is vital to brain function, and it is significantly reduced in ADHD brains.

Many different techniques are used in brain imaging — though not all provide valid or generalizable information — and they give researchers useful glimpses into brain wiring and structure. In order to understand the causes of ADHD better and to treat it more effectively, we need to know the wiring of the brain and how it operates.

The ADHD Brain: Structurally Different

Neuroimaging studies have revealed the structural differences in the ADHD brain. Several studies have pointed to a smaller prefrontal cortex and basal ganglia, and decreased volume of the posterior inferior vermis of the cerebellum — all of which play important roles in focus and attention.

What this means is ADHD is not a difference in behavioral preference. Instead, ADHD appears to be partially attributed to a difference in how the brain is structured. What may look like behavioral choices — laziness, sloppiness, and forgetfulness — are likely due to differences in brain structure.

Researchers at Cambridge, England, and Oulu, Finland, followed 49 adolescents diagnosed with ADHD at age 16 and examined their brain structure and memory function in young adulthood (between 20 to 24 years old), compared to a control group of 34 young adults. The results showed that the group diagnosed in adolescence had reduced brain volume as adults, leading to poorer memory function, even if they no longer met the diagnostic checklist criteria for ADHD. Researchers saw reduced gray matter in a region deep within the brain known as the caudate nucleus, the brain region that integrates information across different parts of the brain and supports cognitive functions, including memory.

Because the structural differences persist into adulthood for most children with ADHD, the chance that a child will outgrow ADHD is not as great as we once thought. Sixty to 75 percent of adults who had ADHD in childhood continue to meet diagnostic criteria in adulthood. Most of those who “outgrow” ADHD continue to manifest many of its symptoms. Adults may score just under the cutoff on diagnostic checklists, but they are likely to continue to have abnormal brain structure, as well as functional impairments in relationships and the workplace.

The Changing Brain

Researchers once thought that each human function was assigned to a specific part of the brain, and that a part damaged by trauma or disease permanently lost its function. Now, research has shown that the human brain changes in response to stimulation; brains have neuroplasticity. The good news is that your brain retains this ability to change from birth to old age. ADHD brains that have deficits in one area will attempt to rewire themselves to accomplish a task.

There are activities that can increase the brain’s effectiveness. Meditation, for example, changes the brain in important ways. Researchers worked with people who’d never meditated before (ADHD was not accounted for as a variable), and put one group through an eight-week mindfulness-based stress-reduction program. The primary difference was in the posterior cingulate, which is involved in mind wandering and self-awareness. Another notable change was in the left hippocampus, which assists in learning, cognition, memory, and emotional regulation. Subsequent studies applied this research using ADHD participants, and similar changes were noticed.

The ADHD Brain: A Network of Its Own

Researchers at Harvard University studied ADHD and non-ADHD subjects as they responded to a challenging cognitive task. While both groups had difficulty with the task, the ADHD group failed to activate their anterior cingulate cortex, which plays two significant roles in attentional processing: adjusting the focus of a person’s attention (where and when) as well as balancing the focus of attention (how much attention for how long). ADHD participants engaged a different, less specialized part of their brain when tackling the task.

What this means. This research highlights what individuals with attention deficit already know. It is difficult to know what to do and when to do it. This is because of an apparent lack of ability to engage the most effective part of their brain, the anterior cingulate cortex.

The default mode network (DMN) represents the regions of the brain that are active when no specific task is being performed — while daydreaming, say, an activity that is undervalued by researchers and society. In the past, this was called the “resting state.” Once functional scans showed how active the brain is at rest, the name was changed.

The DMN takes care of task-irrelevant mental processes, mind-wandering, contemplation, and reflection. It comprises the precuneus/posterior cingulate cortex, the medial prefrontal cortex, and the lateral and inferior parietal cortex. The DMN is more active when individuals are at wakeful rest, engaged in internal tasks, such as daydreaming, recovering memories, and assessing others’ perspectives. Conversely, when individuals work on active, willful, goal-directed tasks, the DMN deactivates, and attentional pathways engage. The DMN and cognitive control networks work in opposing directions to accommodate attentional demands.

In ADHD, the daydreaming brain doesn’t quiet down when the attention circuits turn on. Several studies have focused on the connectivity of the DMN in individuals with ADHD. Weak connections between control centers and the DMN cause an inability to modulate DMN activity. Many studies of children, adolescents, and adults with ADHD, taking and not taking medication, have found that the balance between the cognitive control network and the DMN is either reduced, or absent, in those with ADHD.

The lack of separation between the cognitive control network and the DMN in the ADHD brain suggests why there are attentional lapses. People with ADHD can instruct their focus control system to pay attention to the task at hand — say a pile of bills that need to be paid — but the circuits that connect to the DMN fail to send the instructions to quiet down. When the DMN notices a new magazine lying next to the pile of bills, emotional interest centers light up and overwhelm the weak voice of the cognitive centers.

We have come a long way from our earliest concepts of ADHD as hyperactivity to a dysfunction in the control pathways, but much remains to be studied. Finding which therapies strengthen control centers, which ones improve communication between control centers and action centers, and which ones bypass typical pathways will help adults with the disorder become more productive and confident.

Treating ADHD: What Really Works Best?

“Just tell me one thing so I can get this straight: How much of treating ADHD is medications, and how much is everything else? Is it 50-50? 80-20? Give me a number, so I can wrap my mind around it.” Alex wanted Oren Mason, M.D., a family physician in Grand Rapids, Michigan, to cut to the chase. Alex’s ADHD treatment plan was complex. He was overwhelmed by the recommendations to exercise daily, hire a coach, listen to some ADHD audio books, get more sleep, and start some supplements. The idea of medication sounded promising to him, but the trials needed to find the right dose of the right medication could take months.

“How much bang for the buck do these treatments give?” is a fair question. People with ADHD have already tried dozens of strategies to improve attention and efficiency that, over time, fizzled out.

On one hand, if non-medication therapies were going to successfully treat Alex’s ADHD, they would have done that. He had worked with tutors, therapists, and nutritionist, and read self-help books, but he still had inattention and self-control issues. Medication response can be remarkable, but it isn’t the whole story. Physicians can’t prescribe pills and assume a patient’s ADHD will get better.

Many doctors lack personal experience with ADHD, and don’t understand how much more rigorous the treatment is than the oft-heard “just pop a pill.” Investigators define successful treatment in scientifically accurate terms such as “a 40 percent or better reduction of investigator-rated DSM-V symptomatology, along with a CGI-I score of at least +2.”

Patients, bless them, don’t talk like that. They tend to have goals for successful treatment, such as “get more organized,” “study,” “work to my potential,” and “be more thoughtful” or “be less frustrated with my children.” These goals are hard to express in numbers. They have an “It’s hard to describe, but I’ll know it when I see it” endpoint.

Alex wasn’t asking Dr. Mason to quote studies, just to help him reach some of his goals. Dr. Mason was about to say “50-50,” to emphasize that the effects of medication and non-medication therapies are both important, but what came out was, “They’re both essential. It’s 100-100. Neither of them matters much without the other.”

Researchers have worked on that question and have tried to give us more accurate numbers, even if they aren’t exact. It turns out that you get about 30 percent of what researchers call “the potential response” with medications alone, and about the same from evidence-based non-medication therapies. Using only one therapy alone misses 70 percent of the potential improvement. In other words, if your ADHD were a pie, one evidence-based therapy would eat about one third of it. Use another therapy and 30 percent more would be gone, and so on.

Which is best: medication or the non-medication therapies? The answer is not the scientifically accurate one, but the one that spilled out intuitively that day: 100-100. The best responses come with both therapies done at full-court-press levels.

[Free Resource: Stimulant Medications Chart for the Treatment of ADHD]

13 Comments & Reviews

  1. Medications are helpful but understanding what helps each person reach there fullest potential is very important. Everyone has different Adhd problems. I have two children that are Adhd. One cried in frustration and one acted out. If you listen to them they’ll tell you how to help. You might not like the music I’d always say but stop to hear the lyrics. Most people with Adhd have what I call lagging skills. These skills are things normal people have like communication skills. I tell my son to count to 3 before taking. He’ll say the first thing that comes to mind and we’ll know that isn’t always the best thing to say. The hardest thing to understand with people with Adhd is they’re all different thinkers and handle situations differently. First, accept the problem. Second, what are there lagging skills and last work on improving how they handle these issues.

  2. I believe ADHD to be about the most expensive “dis-ease” to have. If you’re lucky and have really, really, really good insurance, you can get medication and therapy without breaking the bank. Despite the NIH stating that coaching is one of the pillars of ADHD treatment, it isn’t “medical” so isn’t covered by insurance. Add in appropriate supplements, and my estimate is that, even with really good medical insurance, if you get complete appropriate care for ADHD, it will probably cost you $500 a month out of pocket. Since most ADHD adults make, on average, 40% less than their peers in the same field and are usually in fields below what there capabilities might be if they didn’t have the “dis-ease” in the first place (ex: paralegal instead of lawyer; nurse instead of doctor; vet tech instead of veterinarian), most can barely live, let alone get the help they need. There is nothing as frustrating as knowing that, but for a bit of money, you might, just might, be able to live the rest of your life decently. For those of us who were in already well into our failed adulthoods before there was an acknowledgement of ADHD in adults, it’s all too little too late.

  3. This is an excellent article, thank you so much. Hard facts are so important. So much of what you read about ADHD and try to explain to ‘non-believers’ all sounds quite vague and like you’re trying to come up with excuses but this is actual facts and figures so thank you!

  4. This is an excellent article, thank you so much. Hard facts are so important. So much of what you read about ADHD and try to explain to ‘non-believers’ all sounds quite vague and like you’re trying to come up with excuses but this is actual facts and figures so thank you!

    Funny note, I wrote this comment days ago but must have got distracted before pressing post comment 🙂

  5. Thank you for the article. Great content. Could you please share the references to the scientific studies cited in the article? That would be helpful to inform the readers about the significance and magnitude of the results summarized in the article. Thanks again!

  6. For whatever reason, I am not able to reply directly to the comment above about treatment being so expensive. I have ADHD and I’m a stay at home mom. I have a psychology degree and I was identified gifted as a child. I am 49 years old and don’t believe I would be able to hold down a job the way my brain is working right now. I’m doing the best I can with trying to help my kids, especially my daughter, who really seems to be on the extreme end.

    My husband is a police officer and while we do have insurance, no psychologists who are worth their salt take insurance. We can’t afford a coach. We can’t afford a tutor.

    I really feel like I would like to Go back to work, but my husband does not understand what my daughter is going through, because he does not have that as part of his own experience. I feel like I have to be the one to be the front runner on this.

    I am mentally exhausted end it affects my anxiety and depression. I feel like I am not able to help my daughter to the degree that she needs.

  7. As an adult woman with ADHD, I’ve been learning a great deal about ADHD from different perspectives for many years now. I believe that ADHD is the result of childhood trauma which is passed from one generation to the next. I truly believe you will not find a single individual with ADHD that wasn’t subjected to extreme psychological, emotional abuse during the critical developmental years (0-7). I am one such individual.

    If parents raising ADHD children want their lives to improve, they have to work on themselves. ADHD is passed down inter-generationally. Until the adult raising the ADHD child comes to term with their own traumatic childhoods, they won’t be able to help their kids.

  8. cactusflower99
    I was diagnosed in 2018 at age 55 I’m an individual with ADHD that wasn’t subjected to extreme psychological, emotional abuse during the critical developmental years (0-7) since being diagnosed I now believe both my parents were ADHD so were my grandparents on my father’s side, my brother, my nephews, their mother, aunts, and uncles, as well as both my children, all undiagnosed, My children and I, can’t recall any traumas, I can’t really speak for the others apart from to say I know of no trauma, though I had no idea I was ADHD I knew from my own experience how to treat and get the best from my undiagnosed ADHD kids, I had no problem with them, unfortunately, their school was totally inapt and lacked any knowledge on how to care for ADHD kids they caused us no end of grief. Perhaps school was the trauma, thankfully that was all a very long time ago.

  9. Hi cactusflower99, I am deeply sorry to hear that you suffered extreme abuse as a child.

    Your experience, however, is not universal. I have ADHD and did not suffer abuse. My children have ADHD and my wife and I did not abuse them.

    Paying attention to the ADHD research allows us to ‘blame’ the right cause. ADHD is passed down inter-generationally through our genes, not our actions, beliefs or attitudes.

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