ADHD Overview - Part IV - Causes

Summary

This script discusses ADHD as a complex neurodevelopmental disorder influenced by multiple factors, primarily genetic and neurological. It clarifies that social factors like diet or parenting do not directly cause ADHD but can contribute indirectly by increasing biological risks. The script highlights the role of genetics, including familial inheritance and de novo mutations, and environmental factors like prenatal exposure to toxins. It also addresses misconceptions about ADHD medications causing brain damage and emphasizes the disorder's impact on executive functioning networks in the brain, leading to symptoms like inattention and impulsivity.

Takeaways

• 🧬 ADHD arises from multiple sources, including genetic and neurological factors, rather than a single cause.
• 🌐 There is no evidence that ADHD is caused purely by social factors such as diet, parenting, or education.
• 🧫 Poverty can indirectly contribute to ADHD risk through increased exposure to biological risks like malnutrition and substance abuse.
• 🔬 ADHD is associated with genetic and neurological disorders, and can also be acquired through exposure to biological hazards affecting brain development.
• 🧵 Multiple genes are implicated in ADHD, and they may interact with environmental factors to increase the risk of the disorder.
• 🚫 Certain behaviors influenced by ADHD, like risk-taking, can lead to traumatic brain injuries, which in turn can cause or worsen ADHD.
• 🧠 ADHD is classified as a neurodevelopmental disorder due to its impact on the development of the brain's executive network, particularly the frontal lobes.
• 🧠📉 Neuroimaging studies consistently show that people with ADHD have smaller, less active, and less mature brain areas, especially in the frontal lobes, compared to neurotypical individuals.
• 🧠🔄 The brain's executive functions, including inhibition, working memory, emotion regulation, and self-awareness, are impaired in individuals with ADHD.
• 💊 Critics who argue that ADHD medications cause brain damage are incorrect; neuroimaging studies with medication-naïve individuals show the same brain differences.

Q & A

What is the primary cause of ADHD according to the script?

ADHD arises from multiple sources, primarily genetic and neurological factors, rather than a single gene or purely social factors like diet, parenting, or education.

Does poverty directly cause ADHD?

Poverty does not directly cause ADHD, but it can lead to conditions such as malnutrition, increased drug abuse, and pregnancy complications, which are biological factors that can influence brain development and contribute to the risk for ADHD.

What is the role of genetics in ADHD?

Genetics plays a significant role in ADHD, with about 2/3 of ADHD cases being inherited. There are also instances of new mutations (de novo mutations) that can occur in genes that the child inherits, which the parents do not have.

Can environmental toxins or diseases interact with ADHD genes to increase the risk?

Yes, certain genes for ADHD may interact with environmental toxins or diseases to further increase the risk for the disorder. For example, if a child inherits ADHD risk genes and is also exposed to alcohol in utero, the risk for ADHD can be significantly magnified.

How does traumatic brain injury relate to ADHD?

Traumatic brain injuries can cause ADHD even in individuals who did not have it before, and can worsen ADHD in those who already have it. The genes for ADHD can lead to risk-taking behaviors that may result in such injuries.

What is the common pathway for ADHD development mentioned in the script?

Despite the complexity and multiple causes, ADHD arises from a single common pathway affecting the development of the frontal part of the brain and the brain's executive network, often referred to as the fronto-striatal cerebellar network.

What does the script suggest about the size and activity of certain brain areas in people with ADHD?

The script suggests that certain parts of the brain, particularly the frontal lobe, are smaller, less active, and less mature in people with ADHD compared to those without, as shown through neuroimaging studies.

How does ADHD affect the four networks of executive functioning?

ADHD affects the four networks of executive functioning, which include the what network (working memory), the timing network (regulating actions and behaviors), the hot circuit (emotion regulation), and the self-awareness network (awareness of self inside and outside).

What is the relationship between ADHD and the emotional brain?

The emotional brain, which includes the amygdala and the limbic system, is impaired in ADHD, leading to difficulties with emotional control and self-regulation.

How does the script refute the claim that ADHD medications cause brain damage?

The script refutes the claim by stating that neuroimaging studies showing brain differences in ADHD have been repeated with individuals who have never taken ADHD medications, yielding the same results, indicating that the medications do not cause the observed brain differences.

Outlines

00:00

🧬 ADHD's Multifaceted Biological Roots

The paragraph discusses the complex origins of ADHD, emphasizing that it arises from multiple sources rather than a single cause. It clarifies that while genetics play a significant role, environmental factors can also contribute, particularly when they increase the risk for biological factors. The speaker refutes the idea that social factors like diet, parenting, or education directly cause ADHD, but acknowledges that poverty, for example, can indirectly affect ADHD risk through associated biological risks such as malnutrition or substance abuse. The paragraph also touches on the possibility of new genetic mutations leading to ADHD and the interaction between certain genes and environmental toxins or behaviors that can amplify the risk. The overarching message is that ADHD is primarily a result of genetic and neurological factors, with social factors playing a role only insofar as they influence these biological underpinnings.

05:01

🧠 The Impact of ADHD on Brain Development

This paragraph delves into the neurological aspects of ADHD, highlighting that the disorder affects the development of the brain's executive network, particularly the fronto-striatal cerebellar network. It explains that ADHD does not stem from social factors like parenting or screen time, but rather from biological and genetic influences. The speaker references a diagram illustrating the various causes of ADHD and their respective contributions to the disorder's prevalence, with genetics accounting for about two-thirds of cases. The paragraph also addresses the occurrence of ADHD due to new genetic mutations, known as de novo mutations, which can occur in the sperm or egg and are not present in the parents. Additionally, it mentions other factors contributing to ADHD, such as premature birth, low birth weight, exposure to toxins, and certain infections, all of which are rooted in biological mechanisms rather than social ones.

10:02

📊 Neuroimaging Insights into ADHD

The paragraph focuses on neuroimaging studies that reveal consistent patterns of brain differences in individuals with ADHD. It describes how parts of the brain, particularly the frontal lobe and right hemisphere, are smaller, less active, and less mature in people with ADHD compared to neurotypical individuals. The speaker mentions the anterior singulate cortex, basal ganglia, and cerebellum as areas that are particularly affected. The paragraph also addresses the connectivity between the brain's hemispheres and the potential impact of ADHD on the thalamus. The speaker emphasizes that the size and activity levels of these brain areas correlate with the severity of ADHD symptoms. The paragraph concludes by debunking the myth that ADHD medications cause brain damage, clarifying that neuroimaging studies have shown similar brain patterns in individuals who have never taken medication for ADHD.

15:05

🧠 Executive Functioning and ADHD's Brain Circuits

This paragraph explores the concept of ADHD as a disorder of executive functioning, detailing the four key brain circuits that are impaired in individuals with ADHD. The speaker describes the 'what' network, which involves the frontal lobe and basal ganglia and is responsible for working memory and guiding behavior. The 'when' network, involving the cerebellum, governs the timing of actions. The 'how' network, connecting the frontal lobe to the amygdala, is linked to emotional regulation and self-control. Lastly, the 'where' network, involving the parietal lobes, pertains to self-awareness. The paragraph explains how these networks, when dysfunctional, contribute to the symptoms of ADHD, including problems with inhibition, working memory, emotion regulation, and self-motivation. The speaker also discusses the clinical description of ADHD in the context of these executive function networks, emphasizing that ADHD is an executive function disorder rather than merely an attention disorder.

Keywords

💡ADHD

Attention Deficit Hyperactivity Disorder (ADHD) is a neurodevelopmental disorder characterized by symptoms such as inattention, impulsivity, and hyperactivity. In the video, ADHD is discussed as a complex condition arising from multiple biological factors, including genetic and neurological influences. The script emphasizes that ADHD is not caused by social factors like parenting or diet, but rather by biological risks that affect brain development.

💡Genetics

Genetics refers to the study of genes, genetic variation, and heredity in living organisms. In the context of the video, genetics plays a significant role in ADHD, with the script highlighting that multiple genes can interact with environmental factors to increase the risk of ADHD. It also mentions de novo mutations, which are new genetic mutations that occur in a child but were not present in the parents.

💡Neurology

Neurology is the branch of medicine dealing with disorders of the nervous system. The video discusses how ADHD is a neurological disorder, with recognized causes falling within the realm of neurology and genetics. It explains that the development of ADHD is influenced by factors that affect the brain's executive networks, which are crucial for self-control and executive functioning.

💡Executive Functioning

Executive functioning refers to the set of cognitive processes that are necessary for planning, organizing, strategizing, paying attention to and completing tasks, as well as controlling impulses. The video script describes ADHD as adversely affecting the brain's executive network, leading to symptoms such as inattention and impulsivity. It is central to understanding the disorder's impact on an individual's behavior and cognition.

💡Environmental Factors

Environmental factors are external influences that can affect an individual's health or development. The script clarifies that while social factors like diet or parenting do not directly cause ADHD, environmental toxins or conditions such as malnutrition, drug abuse, and premature birth can increase the risk for ADHD by affecting brain development.

💡Neuroimaging

Neuroimaging is the use of various techniques to either directly or indirectly image the structure, function, or pharmacological aspects of the nervous system. The video references neuroimaging studies that show consistent patterns of smaller, less active, and less mature brain areas in people with ADHD, particularly in the frontal lobes and other regions associated with executive functioning.

💡Frontal Lobes

The frontal lobes are the anterior part of the cerebral hemispheres in the brain, responsible for higher cognitive functions like decision-making, planning, and problem-solving. The video script explains that the frontal lobes, especially the orbital frontal area, are often smaller and less active in individuals with ADHD, which is linked to the disorder's symptoms.

💡Working Memory

Working memory is a cognitive system that provides temporary storage and manipulation of information. In the video, it is mentioned as a component of executive functioning that is impaired in ADHD. The script notes that deficits in working memory can contribute to the inattention symptoms observed in individuals with ADHD.

💡Emotional Regulation

Emotional regulation refers to the ability to manage and control one's emotions. The video script discusses how ADHD affects the emotional brain, particularly the amygdala and related structures, leading to difficulties in emotional control and self-regulation, which are common challenges for individuals with ADHD.

💡Self-Awareness

Self-awareness is the capacity for introspection and the ability to recognize and understand one's own emotions, motivations, and actions. The video explains that self-awareness is impaired in ADHD due to the disorder's impact on the brain's executive networks, which include areas responsible for self-reflection and emotional awareness.

Highlights

ADHD arises from multiple sources, not just one, and there is no single gene for ADHD.

ADHD is not caused purely by social factors such as diet, parenting, or education.

Social factors can contribute to ADHD if they increase the risk for a biological factor, such as malnutrition or drug abuse.

There are familial and genetic causes of ADHD, as well as acquired versions due to biological hazards.

Multiple genes can interact with environmental factors to increase the risk for ADHD.

Certain behaviors associated with ADHD, like risk-taking, can lead to brain injuries that cause or worsen ADHD.

ADHD is caused by a single common pathway affecting the development of the brain's executive network.

Genetics accounts for about two-thirds of ADHD cases, with the disorder often running in families.

About 10% of ADHD cases arise from new genetic mutations not present in parents.

The remaining third of ADHD cases come from factors like prematurity, low birth weight, and exposure to toxins.

Neuroimaging studies consistently show that certain brain areas are smaller, less active, and less mature in people with ADHD.

The frontal lobe, particularly the orbital frontal area, is often smaller and less active in individuals with ADHD.

The cerebellum, critical for higher mental activities, is also less active and delayed in development in ADHD.

ADHD is now classified as a neurodevelopmental disorder based on genetic and neuroimaging findings.

There is no evidence that ADHD medications cause brain damage; studies have been repeated with non-medicated individuals.

ADHD is a disorder of executive functioning, affecting inhibition, working memory, emotion regulation, and self-awareness.

Executive functioning in ADHD can be split into two dimensions: inhibition and metacognition.

The clinical description of ADHD fits into an executive theory, with symptoms related to impaired executive functions.

Transcripts

excuse

me we can conclude from thousands of

studies in this area that ADHD arises

from multiple sources not just one so

there's not going to be a single Gene

for ADHD nor is ADHD necessarily always

caused by genetic factors there are

multiple things that interact to lead to

ADHD development

but we know that all of the recognized

causes to date are in the realm of

biology medicine specifically neurology

and

genetics we have no evidence now that

ADHD can arise purely from social

factors such as diet parenting poor

education and so on so that social

factors conditions in society are not

going to cause

ADHD

unless they also increase the risk for a

biological factor so for instance

poverty doesn't cause

ADHD but because being in poverty can

lead to

malnutrition increased drug abuse such

as alcohol and tobacco use it can lead

to increased pregnancy complic

applications and even premature delivery

of the child so all of those biological

risks may occur in impoverished groups

more than others and those are the

factors that are influencing brain

development and through those adverse

influences contribute to risk for ADHD

as well so even where it might look like

a social Factor like economic status is

related to ADHD it's because that factor

is related to other biological risks

that pose harm to the development of the

nervous

system so ADH Le arises largely from

genetic and other neurological factors

we will find that there are people with

ADHD that is familial inherited and

genetic we will all also find some

people with ADHD where their ADHD arises

because of major genetic disorders like

chromosome problems and breakages but

then there's going to be another group

of ADHD that didn't inherit their

disorder or have a genetic problem but

because they were exposed to biological

hazards are going to have problems with

the development of their brain and

especially of the brain's executive

Networks and that is going to give rise

to an acquired version of

ADHD now we also know that there are

multiple genes that cause ADHD and these

genes might interact with some things in

the environment to further increase risk

for example we know that if a child

inherits several of the ADHD risk genes

they may be three to four times more

likely to have

ADHD but if their parents drank alcohol

especially the mother during her

pregnancy with this child it magnifies

the risk to eight times the risk of

having ADHD in that child so certain

genes for ADHD May interact with certain

toxins or diseases in the environment to

further increase the risk for the

disorder and we're beginning to see

evidence of that as

well we also might see that the genetics

of ADHD leads you to engage in certain

risk-taking behaviors that are going to

come back and cause brain injury so for

instance a someone with ADHD takes more

risk becomes more impulsive has more

accidental injuries including traumatic

brain injury or TBI as I say on this

slide and we know that traumatic brain

injuries can cause ADHD even in someone

who didn't have it before and can worse

ADHD in someone who already has it so

there the genes for the disorder create

a behavior pattern that causes a risk

for injury and the injury feeds back to

increase further the risk for and

severity of their

ADHD despite all of this complexity all

of these multiple

causes ADHD arises from a single common

pathway whatever it is we're looking at

as a cause has been shown to have some

effect on the development of the front

part of the brain and the brain's

executive Network often called the

fronto striatal cerebella network but

that's no matter the words here the

terms aren't important what is important

is that there's a network in the brain

that is responsible for self-control for

executive functioning and ADHD adversely

affects that Network and that leads to

the symptoms of the

disorder as I've said there's simply no

evidence that purely social factors like

parenting or like playing video games or

too much screen time on your smart

technology causes ADHD we have no

evidence supporting that so to summarize

what I've said in the last slide in a

picture this is from a book by my good

friend and colleague Dr Joel Nick at the

University of Oregon Health Sciences

Center and it shows in a very simplified

form all of the causes of ADHD and what

percentage or proportion of ADHD cases

is it likely to cause as you can see

here

genetics inheritance accounts for about

2/3 of all cases of ADHD in the

population the disorder runs in families

the child has inherited genes for the

disorder from one or both parents and

other relatives and that increases the

likelihood they're going to have the

same disorder that the relatives had I

do want to point out however that about

10% of ADHD of the cases put in the

genetic category arise from a new

discovery that was shown in the past few

years and that is that new

mutations can occur in the genes that

the child inherits

that the parents don't have these new

mutations often called denovo

mutations can happen in the sperm and

the Egg of the parent so that when we do

a blood test of the parent and we look

at their DNA we don't see any of these

rist genes and yet when we look at the

child's DNA they're there how did they

get there in that

child because at at some point during

the process of

creating the genes in the egg and sperm

that go to the child a mutation took

place and it converted a typical gene

into an ADHD risk Gene and now that

increases the odds the child will have

the disorder even though those genes and

the disorder do not occur in that family

before

then about 10% of ADHD cases arise from

such new

mutations the other third of ADHD cases

as you see here come from the other

factors that I've already mentioned such

as being born prematurely or having a

very low birth weight such that you have

to go into a NE natal intensive care

unit for a while before you're allowed

to be released to your family it can

come from being exposed to toxins like

fetal alcohol exposure other their toxic

ingredients or even consuming lead in

early childhood smoking was thought to

contribute to ADHD but we can now put a

question mark next to that because it

turns out that it may not be the smoking

that smoking is a marker that the parent

has ADHD and that's why they're smoking

during the child's pregnancy so it's not

the smoking it's the fact that adults

with ADHD are more likely to smoke and

it's the genetic relationship between

the parent and the child that's the

cause here the smoking is just a signal

an indicator that the adult excuse me

one of the parents has

ADHD pregnancy complications infections

uh birth complications such as

respiratory distress syndrome and others

can also contribute to injury to the

brain particularly to the front part of

the brain and that could cause risk for

ADHD as well and then there are many

other very small factors here possibly

pesticides vitamin deficiencies

infections with other viruses or

bacteria perhaps for instance the

streptococcal bacteria might also

increase risk for

ADHD so these other factors are also

biological factors but all of this is to

say there is no social Factor on this

diagram that by itself causes

ADHD and it is for that reason that ADHD

has now been classified in our

diagnostic manual as a

neurodevelopmental disorder another

reason for classifying it are the

neuroimaging findings that we see in

hundreds of studies of brain size

connectivity and functioning

excuse

me these studies can be summarized very

simply and I'm oversimplifying what our

very complex research findings that

there are certain parts of the brain

that are smaller less active less mature

in people with ADHD than in typical

people of the same age based on various

neuroimaging measures such as

MRI or fmri or pet scans and so on that

doesn't concern us here what concerns us

is that there's a very consistent

pattern across many of these studies

showing that the frontal lobe

particularly the orbital frontal area

here and also the right side of the

brain more than the left frontal lobe

that are smaller less active and less

mature than they should be the midline

at the frontal low between the two

hemispheres known as the anterior

singulate cortex is also smaller and

less

functional these areas of the brain

project nerve cells networks back into

the central part of the

brain and one of those Central areas is

the basal ganglia and we have found that

this area of the brain is also smaller

less active and delayed in its

development a fourth area is at the back

of the brain the ancient older brain

called the

cerebellum often it's thought that this

is involved in motor coordination in the

timing of our actions and their

smoothness their gracefulness if you

will but we know that the cerebellum is

critical to higher mental activities

like thinking planning and

self-regulation so it's not surprising

to find that parts of the cerebellum are

less active smaller and delayed in

development

more than in typical

people there's some evidence that the

bundle of fibers that connects the left

and right hemispheres of the brain known

as the Corpus

colossum that the front part of that

bundle of nerves the splenium is also

smaller but that would make sense if the

frontal loes are smaller then no

surprise that the fibers of nerves that

connect them would be smaller too little

bit of EV evidence that a structure are

deep in the brain near the basal ganglia

called the thalamus might also be

smaller but that's less certain we do

know that the size of these brain areas

and the degree of activity in them is

directly correlated with how severe your

ADHD is going to be so we have connected

the dots so to speak in the diagram the

neuroimaging findings are related to the

behavioral symptoms

of the disorder and while there's a few

small gender differences between boys

and girls or between men and women

they're not worth mentioning here

because they're not important to our

understanding of ADHD despite the fact

there might be a few

differences critics of

ADHD particularly social critics who are

against giving medication to ADHD such

as the Church of Scientology here in the

United States members of that church

have criticized these findings by saying

that these problems with brain

development were the result of giving

ADHD medications to these children and

that's what caused the injury well of

course that's not true and to prove it

all of these Studies have since been

repeated with children and adults who

never took ADHD medications and we find

exactly the same results so don't let

anybody scare you

into thinking that

ADHD and the medications we use to treat

it that the medication causes the brain

damage it does

not this is just one of hundreds of

studies that illustrates the degree of

delay in ADHD I showed it earlier on my

second slide about the history of ADHD

and what you see here is that the darker

the color the greater the delay is in

the maturation of this out outside area

the gray matter the cortex of the brain

and that it's mainly in the frontal loes

which are here if we look down on top of

the brain which is what the perspective

is here we can see that it's primarily

the frontal loes here's the right and

the left frontal lobe that are delayed

in their development the frontal loes

are the executive brain they allow for

self-regulation to some extent you will

notice the back part of the brain here

is also delayed in

maturation why is that after all these

are the visual centers of the brain well

as I said ADHD greatly interferes with

working memory and one type of working

memory is visual imagery the ability to

reflect and recall images and thoughts

about your past as you think about what

you're going to do we use visual imagery

a lot for self-regulation much like you

use it in your GPS in your car so we

should not be surprised then to see that

some of the centers of the brain related

to working memory particularly visual

imagery are just as delayed as the

frontal executive networks are in the

brain these networks that I'm mentioning

the executive Network can be split into

four different networks and all of them

to one degree or another are impaired

dysfunctional or at least quite variable

in their functioning in people with

ADHD now one of those is from the

frontal lobe into this basal ganglia

that you see here that is the what

network what I think about

information I hold in working memory

reaches back to guide my behavior and

what I'm going to do through the motor

strip and into the basil ganglia the

what network the working memory Network

the second network is going to go from

this part of the brain

through that basil ganglia and there's

your cerebellum that I mentioned earlier

that

network is the timing network of the

brain it's responsible for your sense of

time but more importantly for the timing

of your actions using your sense of time

to guide Behavior to sequence behavior

and to know when to execute a behavior

because when we do something can be as

critical to its success as what we

propose to do that's our timing circuit

and that's why ADHD has been referred to

in my other lectures As Time blindness

it interferes with the guidance of

behavior by our sense of time and leads

to massive problems in time management

in people with

ADHD the third Circuit of the brain is

known as the hot

circuit okay this is the circuit that

goes from the frontal

loes through the midline you can't see

it here of the frontal lobe and down to

the amydala so you see inhibition and

emotion regulation that is what we think

about is going to reach down and control

how we feel the emotions we express and

it's going to allow us to have an

executive control a self-regulation

control over the emotional brain which

starts with the amydala and in general

encompasses the lyic system around here

so that's the emotional brain and that's

the self-control of emotion and you can

see why ADHD individuals have such

difficulty with emotional control the

fourth Circuit of the brain goes from

the frontal lobe again to the midline

that you can't see here right back to

the posterior part of the brain

on both sides often known as the

parietal lobe if I back up you can see

it here on the left or on the yes on the

left side and here on the right side

okay notice that that's a little delayed

too all right that

circuit is

self-awareness awareness of myself in

space which is what the posterior part

of the brain is doing and awareness of

myself internally and

emotionally that's what the anterior

singlet and amydala are doing put them

together and I'm aware of myself outside

and inside selfawareness over time and

now you know why self-awareness is such

a problem for people with ADHD as I've

said the emotional brain is involved in

ADHD you see it here I've already drawn

it for you but it's the frontal lobe

that goes down through the midline and

into the amydala here and this is the

limic system the emotional brain and

that is impaired in ADHD as

well so ADHD while we call it an

attention disorder is understood now to

be a disorder of executive functioning

and of all four networks of executive

functioning leading to problems with

inhibition working

memory

self-restraint emotion

regulation self-

motivation planning and problem solving

along of course with self-awareness if I

didn't mention that already so how can

we fit this new executive theory of

ADHD into the clinical description of

ADHD it's very easy I'll do it

quickly executive functioning is one

thing represented by the light blue box

self-regulation over time to improve our

future we can split this idea or

construct into two

Dimensions two broad dimensions of

behavior and mental

functioning

Innovation and metacognition

the working memory

functions now it can also help if we

take each of these major Dimensions or

mental abilities and carve them up into

very specific minor abilities it helps

us to understand the disorder and

executive functioning better and I've

already described all of these for you

in this presentation earlier there are

many kinds of inhibition

motor verbal mental emotional

motivational and there are kinds of

attention nonverbal working memory

verbal working memory remembering what

you're doing planning and problem

solving and then the ability to manage

emotions once they're

expressed now can you see how ADHD would

fit in here ADHD is comprised of two

Dimensions there's the inhibition

Dimension which we call hyperactive

impulsive behavior but is really a

subset of that executive function

Dimension and then there is the

inattention symptoms which are misnamed

because they're just a subset of the

problem with

metacognition executive attention if you

want to call it that and all of its

components this is really what ADHD is

all about it's an executive function

disorder