Attention Deficit Hyperactivity Disorder: Module 2
Causes and Disorders Sometimes Accompanying
The information in this training module was taken
from an online article by the National Institute of Mental
What Causes ADHD?
One of the first questions
a parent will have is “Why? What went wrong?” “Did I do something to cause
this?” There is little compelling evidence at this time that ADHD can arise
purely from social factors or child-rearing methods. Most substantiated causes
appear to fall in the realm of neurobiology and genetics. This is not to say
that environmental factors may not influence the severity of the disorder, and
especially the degree of impairment and suffering the child may experience, but
that such factors do not seem to give rise to the condition by themselves.
The parents’ focus should
be on looking forward and finding the best possible way to help their child.
Scientists are studying causes in an effort to identify better ways to treat,
and perhaps someday, to prevent ADHD. They are finding more and more evidence
that ADHD does not stem from the home environment, but from biological causes.
Knowing this can remove a huge burden of guilt from parents who might blame
themselves for their child’s behavior.
Over the last few decades,
scientists have come up with possible theories about what causes ADHD. Some of
these theories have led to dead ends, some to exciting new avenues of
Studies have shown a
possible correlation between the use of cigarettes and alcohol during pregnancy
and risk for ADHD in the offspring of that pregnancy. As a precaution, it is
best during pregnancy to refrain from both cigarette and alcohol use.
agent that may be associated with a higher risk of ADHD is high levels of lead
in the bodies of young preschool children. Since lead is no longer allowed in
paint and is usually found only in older buildings, exposure to toxic levels is
not as prevalent as it once was. Children who live in old buildings in which
lead still exists in the plumbing or in lead paint that has been painted over
may be at risk.
One early theory was that
attention disorders were caused by brain injury. Some children who have suffered
accidents leading to brain injury may show some signs of behavior similar to
that of ADHD, but only a small percentage of children with ADHD have been found
to have suffered a traumatic brain injury.
Food Additives and Sugar
It has been suggested that
attention disorders are caused by refined sugar or food additives, or that
symptoms of ADHD are exacerbated by sugar or food additives. In 1982, the
National Institutes of Health held a scientific consensus conference to discuss
this issue. It was found that diet restrictions helped about 5 percent of
children with ADHD, mostly young children who had food allergies.3 A
more recent study on the effect of sugar on children, using sugar one day and a
sugar substitute on alternate days, without parents, staff, or children knowing
which substance was being used, showed no significant effects of the sugar on
behavior or learning.4
In another study, children
whose mothers felt they were sugar-sensitive were given aspartame as a
substitute for sugar. Half the mothers were told their children were given
sugar, half that their children were given aspartame. The mothers who thought
their children had received sugar rated them as more hyperactive than the other
children and were more critical of their behavior.5
Attention disorders often
run in families, so there are likely to be genetic influences. Studies indicate
that 25 percent of the close relatives in the families of ADHD children also
have ADHD, whereas the rate is about 5 percent in the general population.6
Many studies of twins now show that a strong genetic influence exists in the
Researchers continue to
study the genetic contribution to ADHD and to identify the genes that cause a
person to be susceptible to ADHD. Since its inception in 1999, the
Attention-Deficit Hyperactivity Disorder Molecular Genetics Network has served
as a way for researchers to share findings regarding possible genetic influences
Recent Studies on Causes of ADHD
Some knowledge of the
structure of the brain is helpful in understanding the research scientists are
doing in searching for a physical basis for attention deficit hyperactivity
disorder. One part of the brain that scientists have focused on in their search
frontal lobes of the cerebrum.
The frontal lobes allow us to solve problems, plan ahead, understand the
behavior of others, and restrain our impulses. The two frontal lobes, the right
and the left, communicate with each other through the
(nerve fibers that connect the right and left frontal lobes).
are the interconnected gray masses deep in the cerebral hemisphere that serve as
the connection between the cerebrum and the
and, with the cerebellum, are responsible for motor coordination. The cerebellum
is divided into three parts. The middle part is called the
All of these parts of the
brain have been studied through the use of various methods for seeing into or
imaging the brain. These methods include functional magnetic resonance imaging (fMRI)
positron emission tomography (PET), and single photon emission computed
tomography (SPECT). The main or central psychological deficits in those with
ADHD have been linked through these studies. By 2002 the researchers in the NIMH
Child Psychiatry Branch had studied 152 boys and girls with ADHD, matched with
139 age- and gender-matched controls without ADHD. The children were scanned at
least twice, some as many as four times over a decade. As a group, the ADHD
children showed 3-4 percent smaller brain volumes in all regions—the frontal
lobes, temporal gray matter, caudate nucleus, and cerebellum.
This study also showed
that the ADHD children who were on medication had a white matter volume that did
not differ from that of controls. Those never-medicated patients had an
abnormally small volume of white matter. The white matter consists of fibers
that establish long-distance connections between brain regions. It normally
thickens as a child grows older and the brain matures.9
Although this long-term
study used MRI to scan the children’s brains, the researchers stressed that MRI
remains a research tool and cannot be used to diagnose ADHD in any given child.
This is true for other neurological methods of evaluating the brain, such as PET
are finding more and more evidence that ADHD does not stem from the home
environment, but from biological causes.
have shown no possible correlation between the use of cigarettes and alcohol
during pregnancy and risk for ADHD in the offspring of that pregnancy.
disorders often run in families, so there are likely to be genetic influences.
frontal lobes allow us to solve problems, and are the source of gross motor
Disorders that Sometimes Accompany ADHD
Many children with
ADHD—approximately 20 to 30 percent—also have a specific learning disability
(LD).10 In preschool years, these disabilities include difficulty in
understanding certain sounds or words and/or difficulty in expressing oneself in
words. In school age children, reading or spelling disabilities, writing
disorders, and arithmetic disorders may appear. A type of reading disorder,
is quite widespread. Reading disabilities affect up to 8 percent of elementary
A very small proportion of
people with ADHD have a neurological disorder called Tourette syndrome. People
with Tourette syndrome have various nervous tics and repetitive mannerisms, such
as eye blinks, facial twitches, or grimacing. Others may clear their throats
frequently, snort, sniff, or bark out words. These behaviors can be controlled
with medication. While very few children have this syndrome, many of the cases
of Tourette syndrome have associated ADHD. In such cases, both disorders often
require treatment that may include medications.
Oppositional Defiant Disorder
As many as one-third to
one-half of all children with ADHD—mostly boys—have another condition, known as
oppositional defiant disorder (ODD). These children are often defiant, stubborn,
non-compliant, have outbursts of temper, or become belligerent. They argue with
adults and refuse to obey.
About 20 to 40 percent of
ADHD children may eventually develop conduct disorder (CD), a more serious
pattern of antisocial behavior. These children frequently lie or steal, fight
with or bully others, and are at a real risk of getting into trouble at school
or with the police. They violate the basic rights of other people, are
aggressive toward people and/or animals, destroy property, break into people’s
homes, commit thefts, carry or use weapons, or engage in vandalism. These
children or teens are at greater risk for substance use experimentation, and
later dependence and abuse. They need immediate help.
Anxiety and Depression
Some children with ADHD
often have co-occurring anxiety or depression. If the anxiety or depression is
recognized and treated, the child will be better able to handle the problems
that accompany ADHD. Conversely, effective treatment of ADHD can have a positive
impact on anxiety as the child is better able to master academic tasks.
There are no accurate
statistics on how many children with ADHD also have bipolar disorder.
Differentiating between ADHD and bipolar disorder in childhood can be difficult.
In its classic form, bipolar disorder is characterized by mood cycling between
periods of intense highs and lows. But in children, bipolar disorder often seems
to be a rather chronic mood dysregulation with a mixture of elation, depression,
and irritability. Furthermore, there are some symptoms that can be present both
in ADHD and bipolar disorder, such as a high level of energy and a reduced need
for sleep. Of the symptoms differentiating children with ADHD from those with
bipolar disorder, elated mood and grandiosity of the bipolar child are
many as one-third to one-half of all children with ADHD
have another condition, known as oppositional
Many children with ADHD—approximately 20 to 30
percent—also have a specific learning disability . In preschool years,
A very small proportion of
people with ADHD have a neurological disorder called Tourette syndrome.
children with bipolar disorder
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