Nature and Nurture:

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Nature and Nurture Mental Health and Illness
Robert Plomin Institute of Psychiatry London
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Nature? (genetics)
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Nurture? (environment)
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Nature Nurture Controversy

• Nature? Nurture? What do you think?
• Height?
• Weight?
• Mental illness?

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From William Hogarth The Rakes Progress (1735)
1247 Bethlem Hospital (bedlam) 1948 Bethlem
Maudsley IoP
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Institute of Psychiatry Kings College
London Denmark Hill
Regents Park
Thames
Hyde Park
Buckingham Palace
Parliament
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Institute of Psychiatry
Maudsley Hospital

• 300 PhD students, 50 postdocs
• 10 departments including
• Social, Genetic and Developmental Psychiatry
  Centre

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Social, Genetic and Developmental Psychiatry
Centre
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1959 MRC unit in psychiatric genetics
Eliot Slater
1971 first psychiatric genetics text
1953 first twin research
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Social, Genetic and Developmental Psychiatry
(SGDP) Centre
Developmental
Genetic
Social
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Nature and nurture How do we know?

• Does it run in families?
• Does not prove nature could be nurture.

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Nature and nurture How do we know?

• Twin studies
• Identical twins versus non-identical twins
• Adoption studies
• Nonadoptive versus adoptive relatives

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Identical twins (monozygotic, MZ)
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Non-identical, fraternal twins (dizygotic, DZ)
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Psychoses

• Schizophrenia
• Mood disorders
• Unipolar depression
• Bipolar (manic-depression)

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Genetics and schizophrenia
48
Schizophrenia Risk
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9
4
1
Unrelated (population risk) (0)
Second- degree (25)
First- degree (50)
Fraternal twins (50)
Identical twins (100)
Genetic relatedness
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Genain quadruplets
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Nature and nurture How do we know?

• Twin studies
• Identical twins versus non-identical twins
• Adoption studies
• Nonadoptive versus adoptive relatives

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Adoption studies
Genetic relatives
Genetic-plus-environmental relatives
Adoption
Environmental relatives
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Leonard Heston
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Hestons (1966) adoption study
Schizophrenic parents
Nonschizophrenic parents
7
0
Schizophrenic adoptees
Schizophrenic adoptees
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Psychoses

• Schizophrenia
• Mood disorders
• Unipolar depression (major depression)
• Bipolar (manic-depression)

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Family studies of mood disorders
10
8
8
6
4
2
1
0
Population
First-degree relatives
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Twin studies of mood disorders
Twin Concordance ()
Major depression
Bipolar depression
25
Twin studies of other mental illnesses
1.0
DZ
MZ
0.8
0.6
Twin Probandwise concordance
0.4
0.2
0.0
Alcoholism (females)
Alcoholism (males)
Alzheimers disease
Reading disability
Hyperactivity
Autism
Plomin et al. (1994) Science
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Twin studies of common medical disorders
1.0
MZ
DZ
0.8
0.6
Twin Probandwise concordance
0.4
0.2
0.0
Parkinsons disease
Ischemic heart disease
Idiopathic epilepsy
Breast cancer
Hypertension
Peptic ulcer
Chronic obstructive Pulmonary disorder
Rheumatoid arthritis
Plomin et al. (1994) Science
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Perceptions of nature/nurture
indicating that genes are at least as important
as environment (Walker Plomin, 2005)
Percentage with 1-3 responses
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Mental illness nature and nurture

• Importance of nature as well as nurture
• Going beyond nature versus nurture
• Development
• Multivariate
• Nature-nurture interface

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Twins Early Development Study (TEDS)
cognitive
behaviour problems
language
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TEDS twins (7500 pairs)
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TEDS twins assessed at 2, 3, 4, and 7 years
3 years
4 years
7 years
2 years
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Mental illness nature and nurture

• Importance of nature as well as nurture
• Going beyond nature versus nurture
• Development
• Multivariate
• Nature-nurture interface

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Autism spectrum disorders (ASD)
Social

• Has unusual eye gaze, facial expression or
  gestures
• Has at least one good friend (reversed item)
• Has odd style of communication old-fashioned,
  formal, or pedantic

Nonsocial

• Is extremely distressed by changes to routine or
  familiar arrangements
• Has a strong interest in an unusual topic
• Notices small details others might miss

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Social versus nonsocial ASD are different
genetically
Genetic correlation .21
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Implications

• Diagnosis
• Two different disorders
• Molecular genetics
• different genes for
• social and nonsocial

S
N

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Quantitative genetics

• Importance of nature as well as nurture
• Going beyond nature versus nurture
• Development
• Multivariate
• Nature-nurture interface
• Molecular genetics finding DNA

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The Century of the Gene

• 1903 the word gene
• 1953 structure of DNA

• 2003 the human DNA sequence
• 2053 ???

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• Human genome sequences
• 3 billion DNA base pairs
• 3 million DNA differences (gt1 frequency)

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Finding genes

• Some replicated linkages and associations
• Schizophrenia
• Reading disability
• Hyperactivity
• Autism
• Dementia
• Slower progress than expected

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(No Transcript)
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Finding genes What are we looking for?
Answer many QTLs of very small effect
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Rare single-gene disorders
Diagnostic threshold
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The quantitative trait locus (QTL) model for
common complex disorders
Diagnostic threshold
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Schizophrenia linkage and association Dysbindin
(DTNBP1) and neuregulin 1 (NRG1)
Owen et al. (2005) Trends in Genetics 21518-525
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Replicated linkages for reading disability
DCDC2
Fisher DeFries (2002) Nature Reviews
Neuroscience
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Microarrays (gene chips) 1 million DNA markers
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Clinical implications
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Implications for research
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(No Transcript)
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Nature Nurture Controversy

• Not nature versus nurture
• Nature and nurture

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Nature - Nurture misunderstandings

• Cannot separate the effects of nature and nurture
  because both nature and nurture are essential.

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Area of a rectangle depends on length and width
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Nature - Nurture misunderstandings

• Cannot separate the effects of nature and nurture
  because both nature and nurture are essential.
• If genetic, nothing you can do about it.

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Social concerns?

• changing attitudes of parents about childrearing

• educational and occupational discrimination

• prenatal selection designer babies (in vitro
  fertilization, normal conceptions, egg donors)