Fact or Fiction: BiologicalGenetic Basis of ADHD

1
Fact or FictionBiological/Genetic Basis of ADHD

• James M. Swanson
• University of California, Irvine
• Professor of Pediatrics
• Director of UCI Child Development Center

2
UCI-CDC Studies of DRD4 Molecular Genetics of
ADHD

• LaHoste, Swanson, Wigal et al, 1996
• Swanson, Sunohara, Kennedy et al, 1998
• Swanson, Castellanos, Murias, Kennedy, 1998
• Swanson, Sergeant, Taylor et al, 1998
• Swanson, Flodman, Kennedy et al, 2000
• Swanson, Oosterlaan, Murias et al, 2000
• Sunohara, Roberts, Malone et al, 2000
• Swanson, Posner, Fusella at al, 2001
• Swanson, Deutsch, Cantwell et al, 2001
• Barr, Swanson, Kennedy, 2001
• Ding, Chi, Grady et al, 2002
• Swanson, Moyzis et al, 2002

3
UCI-CDC Studies of DRD4 Molecular Genetics of
ADHD

• Fosella, Sommer, Fan et al, 2002
• Goldsmith, Crabbe, Dawson et al, 2003
• Grady, Chi, Ding et al, 2003
• Wang, Ding et al, 2004
• Cornish, Manly, Savage et al, 2005
• Leung, Lee et al, 2005
• Stevenson, Asherson et al, 2005
• Feng, Crosbie et al, 2005
• Grady, Hakxhi et al, 2005
• Grady, Moyzis, Swanson, 2005
• Preston, Kollins, Swanson et al, 2005
• Hay, Bennett, Levy, Sergeant, Swanson, 2006

4
Neuropsychology and Brain Imaging of ADHD

• Swanson, Posner et al, 1991
• Craft et al, 1992
• Nigg, Swanson, Hinshaw, 1997
• Swanson, Castellanos, Murias, Kennedy, 1998
• Swanson, Sergeant, Taylor et al, 1998
• Kupfer et al, 2000
• Swanson, 2000
• Swanson, Oosterlann, Murias et al, 2000
• Volkow, Gatley, Fowler et al, 2000
• Levy and Swanson, 2001
• Volkow, Wang, Fowler et al, 2002

5
Neuropsychology and Brain Imaging of ADHD

• Volkow, Wang, Fowler et al, 2003
• Volkow and Swanson, 2003
• Swanson and Volkow, 2003
• Swanson, 2003
• Volkow, Wang, Ma et al, 2003
• Volkow, Wang, Fowler, Swanson, 2004
• Volkow, Wang, Fowler, Telang et al, 2004
• Volkow, Wang, Ma et al, 2004
• Volkow, Wang, Ma et al, 2005
• Murias, Swanson, Srinivasan, 2006
• Volkow, Wang, Newcorn, et al, 2007

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Summary of A Decade of Research
Neuropsychology Review, 2007
RUTTERS CHILD AND ADOLESCENT PSYCHIATRY, 5TH
EDITION Neurochemistry and Basic
Psychopharmacology Volkow and Swanson, 2007 (in
press)
7
ADHDHistorical Timeline
1960
1980
1968
1987
1994
1930
8
ADHD DSM-IV Criteria for Predominantly
Inattentive Type
Six or more of the following ? manifested often

• Inattention to details/ makes careless mistakes
• Difficulty sustaining attention
• Seems not to listen
• Fails to finish tasks

• Difficulty organizing
• Avoids tasks requiring sustained attention
• Loses things
• Easily distracted
• Forgetful

American Psychiatric Association. DSM-IV, 1994.
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ADHD DSM-IV Criteria for Hyperactive-Impulsive
Type
Six or more of the following ? manifested often

• Impulsivity
• Blurts out answer before question is finished
• Difficulty awaiting turn
• Interrupts or intrudes on others

• Hyperactivity
• Fidgets
• Unable to stay seated
• Inappropriate running, climbing (restlessness)
• Difficulty in engaging in leisure activities
  quietly
• On the go
• Talks excessively

American Psychiatric Association. DSM-IV, 1994.
10
SN
VTA
11
Posner and Raichle, Images of Mind, 1994
(Neuroanatomical Network Theory of Attention)
Alerting(ready for anything)Right frontal
Orienting(prepared for specific)Bilateral
parietal
Executive Control(control of conflict)Anterior
cingulate
Swanson JM, et al. Attention deficit
hyperactivity disorder. In Wilson RA, Keil FC,
eds. The MIT Encyclopedia of the Cognitive
Sciences. Cambridge, MA MIT Press 2001226.
12
SUMMARY OF MRI STUDIES Smaller Brain Structures
in Areas Related to Movement and Attention
Hynd, 1993 19.0 SMALLER Castellanos,
1996 5.4 SMALLER Filipek, 1996 12.7
SMALLER Aylward, 1996 11.8 SMALLER
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Anatomical Sizes (Effect Size ControlADHD)
Larger Posterior and Smaller Anterior Regions
Smaller Than Normal
Caudate Nucleus
Anterior Prefrontal
Rostral Corpus Callosum
1.25 1.00 .75 .50 .25
0 -.25 Effect Size
R
L
R
L
Globus Pallidus
Occipital
Cerebellar Vermis VIII-X
Larger Than normal
Swanson JM, Casey BJ, Nigg J, Castellanos FX,
Volkow ND, Taylor E. (2004).
14
The Dopamine Hypothesis The Cellular Basis of
the DA Deficit
RECEPTOR
TRANSPORTER
15
Positron Emission Tomography (PET)
16
DRD2
DAT

• PET Measures
• DA Transporters
• DA D2 Receptors

17
Dopamine Transporter Density in Patients with
ADHD (Dougherty et al, 1999)
We have shown a 70 increase in age-corrected
dopamine transporter density in patients with
ADHD compared to healthy controls.
18
Volkow et al, 2007, NeuroImage 34
1182-1190Brain DAT levels in treatment naïve
adults with ADHD
Dopamine Transporter Levels Are Lower in
Treatment Naïve Adults with ADHD
19
Extensive PET studies of Methylphenidate in the
Human Brain
11C
methylphenidate
11Cmethylphenidate
Positron Emission Tomography (PET) studies show
that methylphenidate acts predominantly in the
striatum of the human brain where it binds to DA
transporters
20
Pharmacological Treatments of ADHD and
Neuroanatomical Targets

• Multiple reviews of literature by early 1990s
• Wilens and Biederman (1992)
• Psychiatric Clinics North America, The
  Stimulants
• Swanson et al (1993)
• Exceptional Children, Review of Reviews
• Major change in early 2000 to controlled delivery
• Swanson, Gupta et al (1999)
• Clin Pharm Ther, Acute tolerance to MPH
• Greenhill et al (2003)
• JAACAP, PK/PD of Adderall
• Recent increase in non-stimulant medications

21

• Threshold Dose
• Brain Pharmacokinetics
• Individual Differences
• Context of Administration

22
Volkow and Swanson, 2007 (in press)RUTTERS
CHILD AND ADOLESCENT PSYCHIATRY, 5TH EDITION
Neurochemistry and Basic Psychopharmacology
Pharmacokinetic
Pharmacodynamic
Brain
Synapse
Circuit
Blood
Absorption (ka)
Emotion
Transporters
Ce(t)
Ee(t)
C(t)
E(t)
Distribution (ke)
Enzymes
Cognition
Elimination (keo)
Receptors
Side Effects
23
PET Imaging and Brain Pharmacokinetics of
Methylphenidate (Volkow et al, 1995)
11CMethylphenidate
PK half-life 1.5 hr
Behavioral half-life .3 hr
24
PET Studies of Mechanism of Action DAT
Blockade by Oral MPH
DAT Occupancy ()
Volkow ND, et al. Synapse. 19993159.Volkow ND,
et al. Synapse. 200243181.
Dose (mg/kg)
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Effects of Oral MP on Extracellular DA
p lt 0.0005
Bmax/kd
Placebo
Oral MP
Therapeutic doses of oral MP significantly
increase extracellular DA in the human brain
Volkow et al. (2001) J Neuroscience, 211-5.
26
Methylphenidate (MPH) Blocks the Dopamine
Transporter (DAT) and Increases Signal
MAO A
DA
DA
DA
DA
DA
DA
DA
signal
27
Brain areas with significantly changed cerebral
blood flow (CBF) after methylphenidate treatment
(assessed by paired t-test between baseline and
posttreatment conditions) in ADHD patients.
Red-yellow, increased CBF after treatment
blue-cyan, decreased CBF after treatment. Lee JS
et al. Hum Brain Mapp. 200524157-164.
28
DA Deficit Hypothesis of ADHD
Wender, (1971) Levy (1990)
29
Biological Bases of ADHD
The Dopamine Hypothesis
RECEPTOR
TRANSPORTER
30
D4 RECEPTOR and the 48 bp Variable Number of
Tandem Repeats (VNTR)
2 Repeat
4 Repeat
7 Repeat
CCC-GCG-CCC-CGC-CTC-CCC-CAG-GAC-CCC-TGC-GGC-CCC-GA
C-TGT-GCG-CCC 1 2 3 4
5 6 7 8 9 10 11
12 13 14 15 16
31
Alleles of the DRD4 Gene for Possible Offspring
32
Molecular Genetic Approaches
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34
UCI-CDC Studies of DRD4 Molecular Genetics of
ADHD

• LaHoste, Swanson, Wigal et al, 1996
• Swanson, Sunohara, Kennedy et al, 1998
• Swanson, Castellanos, Murias, Kennedy, 1998
• Swanson, Sergeant, Taylor et al, 1998
• Swanson, Flodman, Kennedy et al, 2000
• Swanson, Oosterlaan, Murias et al, 2000
• Sunohara, Roberts, Malone et al, 2000
• Swanson, Posner, Fusella at al, 2001
• Swanson, Deutsch, Cantwell et al, 2001
• Barr, Swanson, Kennedy, 2001

35
LaHoste, SwansonKennedy, 1996, Molecular
Psychiatry, 1121-124 Swanson, Sunohara,
Kennedy, 1998, Molecular Psychiatry, 3 38-41
36
DAT
DRD4
gt 1.0 Risk
Genome Scans Followed the Candidate Gene Studies
of ADHD Recent study identified 18 risk genes
for ADHD DRD4 and DAT genes confirmed and 16
other risk genes suggested
37
UCI-CDC Studies of DRD4 Molecular Genetics of
ADHD

• LaHoste, Swanson, Wigal et al, 1996
• Swanson, Sunohara, Kennedy et al, 1998
• Swanson, Castellanos, Murias, Kennedy, 1998
• Swanson, Sergeant, Taylor et al, 1998
• Swanson, Flodman, Kennedy et al, 2000
• Swanson, Oosterlaan, Murias et al, 2000
• Sunohara, Roberts, Malone et al, 2000
• Swanson, Posner, Fusella at al, 2001
• Swanson, Deutsch, Cantwell et al, 2001
• Barr, Swanson, Kennedy, 2001

38
Components of Tasks Designed to Measure Executive
Control

• Executive control deficits would produce
• In the Stroop Color-Conflict Task, an increased
  cost of incongruent and reduced benefits of
  congruent
• In the Posner Cued-Detection Task, increased
  costs of Invalid or No cues
• In Logan Go-Change Task, slow responding in the
  change condition

39
Swanson et al. (2000) PNAS, 974754-4759ADHD
children with a 7-repeat allele of the dopamine
receptor D4 gene have extreme behavior but normal
performance on critical tests
Average RT
Normal performance on critical neuropsychological
tests
40
Langley et al, American Journal Psychiatry, 2003
ADHD children with and without the dopamine D4
receptor 7-repeat allele Performance on
neuropsychological tests 
41
Next Questions

• Why does one allele (7R) of the DRD4 gene protect
  children with ADHD from cognitive deficits?
• Does the 7 genotype confer some unusual
  advantage?
• Does the 7- genotype confer some disadvantage?

42
UCI-CDC Studies of DRD4 Molecular Genetics of
ADHD

• Ding, Chi, Grady et al, 2002
• Swanson, Moyzis et al, 2002
• Fosella, Sommer, Fan et al, 2002
• Goldsmith, Crabbe, Dawson et al, 2003
• Grady, Chi, Ding et al, 2003
• Wang, Ding et al, 2004
• Cornish, Manly, Savage et al, 2005
• Leung, Lee et al, 2005
• Stevenson, Asherson et al, 2005
• Feng, Crosbie et al, 2005
• Grady, Hakxhi et al, 2005
• Preston, Kollins, Swanson et al, 2005

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D4 RECEPTOR and the 48 bp Variable Number of
Tandem Repeats (VNTR)
2 Repeat
4 Repeat
7 Repeat
CCC-GCG-CCC-CGC-CTC-CCC-CAG-GAC-CCC-TGC-GGC-CCC-GA
C-TGT-GCG-CCC 1 2 3 4
5 6 7 8 9 10 11
12 13 14 15 16
45
Gel-based allele length
Nucleotide sequence
46
48 bp VNTR (imperfect repeat)
CCC-GCG-CCC-CGC-CTC-CCC-CAG-GAC-CCC-TGC-GGC-CCC-GA
C-TGT-GCG-CCC 1 2 3 4
5 6 7 8 9 10 11
12 13 14 15 16
2
3
4
1
CCC GCG CCC GGC CTT CCC CGG GGT CCC TGC GGC CCC GA
C TGT GCG CCC
CCC GCG CCC GGC CTC CCC CCG GAC CCC TGC GGC TCC AA
C TGT GCT CCC
GCC GCG CCC AGC CTC CCC CAG GAC CCC TGT GGC CCC GA
C TGT GCG CCC
CCC GCG CCC CGC CTC CCC CAG GAC CCC TGC GGC CCC GA
C TGT GCG CCC
47
Nucleotide Variation Across Repeats(Lichter,
Barr, Kennedy et al, 1993)
10 20 30
40 48 (a) 1 A CCC GCG CCC CGC
CTC CCC CAG GAC CCC TGC GGC CCC GAC TGT GCG CC
Pro Ala Pro Arg Leu Pro Gln Asp Pro Cys Gly Pro
Asp Cys Ala Pro   (b) 2 C ... ... ... G.. ..T
... .G. .GT ... ... ... ... ... ... ... ..
Gly Arg Gly   (q) 3 C G.. ...
... A.. ... ... ... ... ... ..T ... ... ... ...
... .. Ala Ser   (h) 4 C ... ... ...
G.. ... ... .C. ... ... ... ... T.. A.. ... ..T
.. Gly Pro Ser
Asn   (e) 5 C ... ... ... G.. ... ... ... ...
... ... ... ... ... ... ... ..
Gly   (z) 6 C G.. ... ... G.. ... ... .C. ...
... ... ... ... ... ... ... .. Ala
Gly Pro   (g) 7 C ... ... ... G.. ..T
... ... ... ... ..T ... ... ... ... ... ..
Gly  
48
New Sequence Variants (1)
20 C G.. ... ... G.. ... ... .C. ... ... ... ...
T.. A.. ... ..T .. Ala Gly
Pro Ser Asn   21 C G.. ... ...
A.. ... ... ... ... ... ... ... T.. A.. ... ..T
.. Ala Ser
Ser Asn   22 C G.. ... ... G.. ... ... ...
... ... ... ... T.. A.. ... ..T .. Ala
Gly Ser
Asn   23 C ... ... ... G.. ... ... ... ... ...
..T ... ... ... ... ... ..
Gly   24 . ... ... ... G.. ..T ... .G. .GT ...
... ... ... ... ... ... ..
Gly Arg Gly   25 C G.. ... ... A.. ...
... .C. ... ... ... ... ... ... ... ... ..
Ala Ser Pro   26 C ... ... ...
G.. ..T ... .G. .TT ... ... ... ... ... ... ...
.. Gly Arg
Val   27 C ... ... ... G.. ... ... .C. ... ...
... ... ... ... ... ... ..
Gly Pro  
49
Asymmetric Crossover of Two 4R ALLELES
1-2-3-4
1-2-3-4
1-2-3-4

• Combinations of motifs define nucleotides in
  the sequence of an allele
• Most nucleotide sequences are based on the 4R
  allele (motifs 1-2-3-4)
• Recombination of two 4R alleles can produce a 2R
  allele

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Variation in the 48 base-pair repeat motif
MOTIF SEQUENCE 1 3
A CCC GCG CCC CGC CTC CCC CAG GAC CCC TGC GGC CCC
GAC TGT GCG CC Pro Ala Pro Arg Leu Pro Gln Asp
Pro Cys Gly Pro Asp Cys Ala Pro
C G.. ... ... A.. ... ... ... ... ... ..T ... ...
... ... ... .. Ala Ser

C ... ... ... G.. ... ... .C. ... ... ... ... T..
A.. ... ..T .. Gly Pro
Ser Asn
4
C G.. ... ... A.. ... ... ... Ala Ser
... ... ... ... T.. A.. ... ..T ..
Ser Asn
21
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UCI-CDC Studies of DRD4 Molecular Genetics of
ADHD

• Ding, Chi, Grady et al, 2002
• Swanson, Moyzis et al, 2002
• Fosella, Sommer, Fan et al, 2002
• Goldsmith, Crabbe, Dawson et al, 2003
• Grady, Chi, Ding et al, 2003
• Wang, Ding et al, 2004
• Cornish, Manly, Savage et al, 2005
• Leung, Lee et al, 2005
• Stevenson, Asherson et al, 2005
• Feng, Crosbie et al, 2005
• Grady, Hakxhi et al, 2005
• Preston, Kollins, Swanson et al, 2005

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Ding et al., PNAS, 2002, 99, 309-314Evidence of
Positive Selection Acting at the Humand Dopamine
Receptor D4 Gene Locus
Exon 3 Sequences for 36 DRD4 Alleles
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Haplotypes of 600 DRD4 Exon 3 Alleles  Allele F N
Haplotype Allele F N Haplotype 2R .088 55
6R .022 24 43 1-4 16 1-2-3-2-3-4
12 30-4 2 1-2-6-5-2-20 3R .024 36 2
1-2-6-5-2-4 16 1-7-4 1 1-2-14-17-2-4 9 1
-2-4 1 1-6-5-2-5-4 4 1-11-33
1 1-2-13-2-5-19 3 1-9-4 1 24-6-5-2-5-4
1 1-2-22 7R .192 199 1 1-2-21 177 1-2-6
-5-2-5-4 1 1-2-31 5 1-2-6-5-2-5-19
1 1-2-32 3 1-2-6-5-2-3-4 4R .651 250 3
1-2-6-5-13-5-4 238 1-2-3-4 2 1-8-25-5-2-5
-4 3 1-2-14-4 2 1-2-3-5-2-5-4 2 1-2-13-4
1 1-2-6-5-2-13-4 2 1-2-12-4 1 1-2-29-17-2
-5-4 1 1-17-3-4 1 1-2-6-2-2-5-4 1 1-9-12-
4 1 1-8-25-5-2-3-4 1 1-8-3-4 1 1-2-6-16-2
-3-4 1 1-10-3-4 1 1-2-6-5-2-14-4 1 1-9-3-
4 1 1-2-3-17-2-5-4 5R .016 27 8R .006
6 12 1-3-2-3-4 2 1-2-6-5-17-2-13-35
4 1-2-13-34-4 1 1-2-6-5-2-2-5-4 3 1-2-
2-3-4 1 1-2-6-26-5-26-3-35 2 1-2-6-5-4 1
1-2-6-26-5-26-3-4 2 1-11-2-3-4 1 1-2-6-18-5-
18-3-4 1 1-3-2-14-4 1 1-2-6-23-4 9R lt.
001 1 1-8-25-5-2-5-2-23-4 1 1-2-3-9-4 10R lt.00
1 1 1-2-15-6-2-6-5-2-5-4 1 1-2-3-27-4 11R lt.00
1 1 1-2-3-27-5-23-25-5-2-5-28   F observed
allele frequency in 2836 chromosomes from 37
worldwide human populations. (Chang et al,
1996) N allele number identified by sequence
analysis in this study non-4R alleles were
oversampled by 2-3 fold. Alleles with adjacent
asterisks indicate common variants found only in
a single population sample (2R 30-4, surui 3R
1-11-33, nasioi 5R 1-3-2-3-4, chinese 5R
1-2-13-34-4, biaka 7R 1-2-6-5-2-5-19, surui 7R
1-2-6-5-13-5-4, nasioi 8R 1-2-6-5-17-2-13-35,
biaka). Alleles with a single representation
were, by definition, found in only one
population.  
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1-2-3-4
L L S S
G - G
A - C
4R-ALLELE
Multiple Mutations/ Gene Conversions
1-2-3-4
55
DRD4 Gene with 70 SNPs for 103 Individuals
1
70
1
(51)
(43)
(9)
103
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Ding et al., 2002, PNAS, 99309-314

• The 2R to 6R-alleles can be explained by one-step
  unequal recombination events between 4R alleles.
• The formation of the 7R allele would require gt1
  recombination and multiple (gt6) mutations.
• Intraallelic variability est. of allele age
  indicate that the 7R-allele is 10 fold younger
  than the 4R allele.
• Allelic variability of 4R (but not 7R) alleles in
  African DNA is greater than from other sources.

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MIGRATION PATHS OUT OF AFRICA INTO NEW
WORLD (Chen et al., 1999, Evolution and Human
Behavior, 20309-324)
P(7R) .15
P(7R) .26
P(7R) .63
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CBS 60 Minutes, 12/5/04ATTENTION DEFICIT
DISORDER GROWS UP
59
David Neeleman
David Neeleman says he always knew his brain
worked a little differently from the rest. "I
scored so low on the English portion of the ACT
test that my counselor hauled me in and said,
'David, had you just answered 'C' on every
question, you would've done better. You would've
done 30 percent better than what you did,' says
Neeleman. He spent years in various jobs, in a
sort of limbo, before he realized he had a
clear-cut case of ADD. Even so, hes a huge
success. He's CEO of Jet Blue, the low-cost,
no-frills carrier that has shaken up the airline
industry.
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David Neeleman
Neeleman says many of his out-of-the-box ideas
are thanks to his ADD. "In the midst of all the
chaos in your mind, and all of the
disorganization, and all the trouble getting
started, and procrastination, your brain just
thinks a little bit differently," he says. "And
you can come up with things." Ideas like
e-tickets, or ticketless travel, which is perfect
for someone who is always losing things, and live
TV, is making a his company profit while most of
the airline industry is in trouble. But having
finally discovered he had a certifiable medical
condition, Neeleman decided to do absolutely
nothing about it.
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David Neeleman
He says that many ADD sufferers are attracted to
high-risk or entrepreneurial careers. And his
list of people he thinks may have ADD include
Bill Clinton, and Richard Branson. Theres also
speculation that some great figures in history
had ADD and led tortured but productive lives --
Leonardo Da Vinci, Pablo Picasso, Winston
Churchill. And, ADD websites claim that Thomas
Edison had ADD, which leads one to wonder if
Edison had been on medication, he might have
invented the pogo stick instead of the light
bulb. "The idea of treatment isn't to confine
people and take away their creativity," says
Adler. "It's really to try to help them be more
productive and tap into their creativity."
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Neuropsychology Review, 2007
63
Two Presumed Etiologies

• Environmental
• Preterm birth
• Smoking during pregnancy
• Genetic
• Dopamine genes (DRD4 and DAT)
• Genome scan

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National Childrens Study (NCS)

• Study of environmental influences on children's
  health
• Longitudinal cohort study birth to 21 years
• National in scope in 96 representative counties
• Enrollment during or before pregnancy
• Large sample size (100,000 live births)
• Exposure broadly defined (physical, chemical,
  biological, and psychosocial)
• Outcome broadly defined (priorities
  pregnancy-related injury asthma obesity,
  diabetes, physical development child development
  and mental health)
• Evaluation of gene-environment interactions

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