ADHD Overview - Part IV - Causes
Summary
TLDRThis 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
🧬 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.
🧠 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.
📊 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.
🧠 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.
Mindmap
Keywords
💡ADHD
💡Genetics
💡Neurology
💡Executive Functioning
💡Environmental Factors
💡Neuroimaging
💡Frontal Lobes
💡Working Memory
💡Emotional Regulation
💡Self-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
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