Title: 
Headings: Neurodevelopmental Disorders
Neurodevelopmental
 
Disorders
 

Attention-Deficit/Hyperactivity
 
Disorder
 
(ADHD)
 

Learning
 
Disability

Autism
 
Spectrum
 
Disorders
 

Intellectual
 
Disability
 
(Mental
 
Retardation)
 

Indicators
 
in
 
this
 
Section
 

Indicator
 
H9:
 
Percentage
 
of
 
children
 
ages
 
5
 
to
 
17
 
years
 
reported
 
to
 
have
 
intellectual
 
disability
 
(mental
 
retardation),
 
1997–2013
 

National
 
Health
 
Interview
 
Survey
 

Data
 
Presented
 
in
 
the
 
Indicators
 

Other
 
Estimates
 
of
 
ADHD
 
and
 
Autism
 
Prevalence
 

References


Content: However,
 
most
 
neurodevelopmental
 
disorders
 
have
 
complex
 
and
 
multiple
 
contributors
 
rather
 
than
 
any
 
one
 
clear
 
cause. These
 
disorders
 
likely
 
result
 
from
 
a
 
combination
 
of
 
genetic,
 
biological,
 
psychosocial
 
and
 
environmental
 
risk
 
factors. A
 
broad
 
range
 
of
 
environmental
 
risk
 
factors
 
may
 
affect
 
neurodevelopment,
 
including
 
(but
 
not
 
limited
 
to)
 
maternal
 
use
 
of
 
alcohol,
 
tobacco,
 
or
 
illicit
 
drugs
 
during
 
pregnancy; lower
 
socioeconomic
 
status; preterm
 
birth; low
 
birthweight; the
 
physical
 
environment; and
 
prenatal
 
or
 
childhood
 
exposure
 
to
 
certain
 
environmental
 
contaminants.14-21
  
Lead,
 
methylmercury,
 
and
 
PCBs
 
are
 
widespread
 
environmental
 
contaminants
 
associated
 
with
 
adverse
 
effects
 
on
 
a
 
child’s
 
developing
 
brain
 
and
 
nervous
 
system
 
in
 
multiple
 
studies. The
 
National
 
Toxicology
 
Program
 
(NTP)
 
has
 
concluded
 
that
 
childhood
 
lead
 
exposure
 
is
 
associated
 
with
 
reduced
 
cognitive
 
function,
 
including
 
lower
 
intelligence
 
quotient
 
(IQ)
 
and
 
reduced
 
academic
 
achievement.22
 
The
 
NTP
 
has
 
also
 
concluded
 
that
 
childhood
 
lead
 
exposure
 
is
 
associated
 
with
 
attention-related
 
behavioral
 
problems
 
(including
 
inattention,
 
hyperactivity,
 
and
 
diagnosed
 
attention-deficit/hyperactivity
 
disorder)
 
and
 
increased
 
incidence
 
of
 
problem
 
behaviors
 
(including
 
delinquent,
 
criminal,
 
or
 
antisocial
 
behavior).22
  
EPA
 
has
 
determined
 
that
 
methylmercury
 
is
 
known
 
to
 
have
 
neurotoxic
 
and
 
developmental
 
effects
 
in
 
humans.23
 
Extreme
 
cases
 
of
 
such
 
effects
 
were
 
seen
 
in
 
people
 
prenatally
 
exposed
 
during
 
two
 
high-dose
 
mercury
 
poisoning
 
events
 
in
 
Japan
 
and
 
Iraq,
 
who
 
experienced
 
severe
 
adverse
 
health
 
effects
 
such
 
as
 
cerebral
 
palsy,
 
mental
 
retardation,
 
deafness,
 
and
 
blindness.24-26
 
Prospective
 
cohort
 
studies
 
have
 
been
 
conducted
 
in
 
island
 
populations
 
where
 
frequent
 
fish
 
consumption
 
leads
 
to
 
methylmercury
 
exposure
 
in
 
pregnant
 
women
 
at
 
levels
 
much
 
lower
 
than
 
in
 
the
 
poisoning
 
incidents
 
but
 
much
 
greater
 
than
 
those
 
typically
 
observed
 
in
 
the
 
United
 
States. Results
 
from
 
such
 
studies
 
in
 
New
 
Zealand
 
and
 
the
 
Faroe
 
Islands
 
suggest
 
that
 
increased
 
prenatal
 
mercury
 
exposure
 
due
 
to
 
maternal
 
fish
 
consumption
 
was
 
associated
 
with
 
adverse
 
effects
 
on
 
intelligence
 
and
 
decreased
 
functioning
 
in
 
the
 
areas
 
of
 
language,
 
attention,
 
and
 
memory.26-32
 
These
 
associations
 
were
 
not
 
seen
 
in
 
initial
 
results
 
reported
 
from
 
a
 
similar
 
study
 
in
 
the
 
Seychelles
 
Islands.33
 
However,
 
further
 
studies
 
in
 
the
 
Seychelles
 
found
 
associations
 
between
 
prenatal
 
mercury
 
exposure
 
and
 
some
 
neurodevelopmental
 
deficits
 
after
 
researchers
 
had
 
accounted
 
for
 
the
 
developmental
 
benefits
 
of
 
fish
 
consumption.34-36
 
More
 
recent
 
studies
 
conducted
 
in
 
the
 
United
 
States
 
have
 
found
 
associations
 
between
 
neurodevelopmental
 
effects
 
and
 
blood
 
mercury
 
levels
 
within
 
the
 
range
 
typical
 
for
 
U.S.
 
women,
 
after
 
accounting
 
for
 
the
 
beneficial
 
effects
 
of
 
fish
 
consumption
 
during
 
pregnancy.32,37,38
  
Several
 
studies
 
of
 
children
 
who
 
were
 
prenatally
 
exposed
 
to
 
elevated
 
levels
 
of
 
polychlorinated
 
biphenyls
 
(PCBs)
 
have
 
suggested
 
linkages
 
between
 
these
 
contaminants
 
and
 
neurodevelopmental
 
effects,
 
including
 
lowered
 
intelligence
 
and
 
behavioral
 
deficits
 
such
 
as
 
inattention
 
and
 
impulsive
 
behavior.39-44
 
Studies
 
have
 
also
 
reported
 
associations
 
between
 
PCB
 
exposure
 
and
 
deficits
 
in
 
learning
 
and
 
memory.39,45
 
Most
 
of
 
these
 
studies
 
found
 
that
 
the
 
effects
 
are
 
associated
 
with
 
exposure
 
in
 
the
 
womb
 
resulting
 
from
 
the
 
mother
 
having
 
eaten
 
food
 
contaminated
 
with
 
PCBs,46-51
 
although
 
some
 
studies
 
have
 
reported
 
relationships
 
between
 
adverse
 
effects
 
and
 
PCB
 
exposure
 
during
 
infancy
 
and
 
childhood.45,51-53
 
Although
 
there
 
is
 
some
 
inconsistency
 
in
 
the
 
epidemiological
 
literature,
 
several
 
reviews
 
of
 
the
 
literature
 
have
 
found
 
that
 
the
 
overall
 
evidence
 
supports
 
a
 
concern
 
for
 
effects
 
of
 
PCBs
 
on
 
children’s
 
neurological
 
development.52,54-58
 
The
 
Agency
 
for
 
Toxic
 
Substances
 
and
 
Disease
 
Registry
 
has
 
determined
 
that
 
“Substantial
 
data
 
suggest
 
that
 
PCBs
 
play
 
a
 
role
 
in
 
neurobehavioral
 
alterations
 
observed
 
in
 
newborns
 
and
 
young
 
children
 
of
 
women
 
with
 
PCB
 
burdens
 
near
 
background
 
levels.