Causes of Schizophrenia
嚜燕syc 311 每 Abnormal Psychology
Causes of Schizophrenia
? Actual cause is not known
? Appears to be an interaction between
vulnerabilities and environmental stress
Causes of Schizophrenia
Psychology 311
Abnormal Psychology
Listen to the audio lecture while viewing these slides
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Psyc 311 每 Abnormal Psychology
Psyc 311 每 Abnormal Psychology
Many Different Hypotheses
Genetic Contributions
?
?
?
?
?
? The closer the relative, the higher the
probability for schizophrenic
Genetics
Prenatal Factors
Dopamine Hypothesis
Schizophrenic Spectrum Hypothesis
Diathesis Stress Model
? Highly probable schizophrenia is genetic
? Is probably not caused by one gene
? Would show in all monozygotic twin
studies.
? Is probably caused by the combination of
several genes.
? Not totally sure which ones
? Has been identified with genes on
Chromosome 22 and Chromosome 6.
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Psyc 311 每 Abnormal Psychology
Psyc 311 每 Abnormal Psychology
Prenatal Factors Hypothesis
Neurodevelopmental Model
? Individuals exposed to a Flu virus in
second trimester had higher rates of
schizophrenia than a control group not
exposed.
? High stress shown in widowed Finnish
women
? Contends some abnormality may occur in
prenatal neurological development
? Example
? Second semester
? Cells migrate from original position to distant
locations where they establish connections
? Schizophrenics brains are different than
※Normals§
? When Russia invaded Finland in 1959,
women had higher schizophrenia rates
More cells were in deeper layers of the cortex than
the surface
? Indicates neurons did not migrate as far as they
should have
?
? Birth complications correlated with
schizophrenia
? Suggests brain damage
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Psyc 311 每 Abnormal Psychology
Psyc 311 每 Abnormal Psychology
Prenatal Development Abnormalities
Dopamine Hypothesis
? Reflected in
? Contends:
? Minor physical anomalies
? Positive symptoms occur due to increased
levels of Dopamine.
? Get increased stimulation of
Dopaminergic synapses
Malformed ears
? Unusual spacing of tear ducts
? Arched Palate of the mouth
?
? Excessive receptor activation is
correlated with hallucinations
? Neuromotor anomalies
Many unusual expressions
? May hold hands in unusual manner
?
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Psyc 311 每 Abnormal Psychology
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Psyc 311 每 Abnormal Psychology
Support for Hypothesis
Schizophrenic Spectrum Disorder
Hypothesis
? Drugs that increase dopamine levels
(Amphetamine, Cocaine) can produce
positive symptoms of schizophrenia
? Contends schizophrenic patients often
have relatives that are eccentric or have
bizarre behaviors
? May be a genetic inheritance
? Combination of
? Drugs that block DA receptors also
reverse schizophrenia
emotional responses
cognitive behavior
? some personality disorders
?
?
? Can reduce positive symptoms in 80% of
patients
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Psyc 311 每 Abnormal Psychology
Psyc 311 每 Abnormal Psychology
Example 每 Schizotypal Personality
Disorder
Families
?
?
?
?
?
? Seems closest genetically to
schizophrenia
? Behaviors are milder forms of
schizophrenia
?
?
?
?
?
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Odd speech patterns
Social dysfunction
Aloofness
Odd communication
Suspiciousness
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Paranoid personality disorder
Schizoid personality disorder
Others
All appear in families with schizophrenia
Gene on chromosome 8 is linked to the
spectrum of disorders and schizophrenia
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Psyc 311 每 Abnormal Psychology
Psyc 311 每 Abnormal Psychology
Family Studies are Useful
Associative Mating
? Allows you to look for schizophrenia or
other disorders
? Make a family tree of disorders
? Tendency to choose a mate that is
genetically similar than would be
expected by chance
? Result
? Can get an idea of the full spectrum of
disorders
? Children from these marriages may end
up with ※double doses§ of bad genes
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Psyc 311 每 Abnormal Psychology
Psyc 311 每 Abnormal Psychology
Gottesman (1991)
Twin Studies
? Conducted five studies of associative
mating
? Risk for children increases 46% vs. 17%
with only one parent affected
? Allow you to control for hereditary
factors
? MZ twins
? Higher concordance rates for
schizophrenia
? Problem only 50% have it
?
Conclusion 每 Heredity is not enough alone
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Psyc 311 每 Abnormal Psychology
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Psyc 311 每 Abnormal Psychology
Examine When Twin Becomes
Schizophrenic
Adoption Studies
? Is another way to study hereditary
factors
? Child is not raised by biological parents
? Some studies - 5 years old
? More studies 每 13 years old
? Most common age 14 - 16
? Show more schizophrenia
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Psyc 311 每 Abnormal Psychology
Psyc 311 每 Abnormal Psychology
Environmental Factors
Diathesis Stress Model
? Contends
? Contends the disorder is an interaction
of genetic and environmental factors
? You can have a genetic or biological
predisposition
? Problem, what causes the disorder to
express itself
(Zurbin, 1983)
? Is not a permanent disorder but a
permanent vulnerability
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Psyc 311 每 Abnormal Psychology
Psyc 311 每 Abnormal Psychology
Community Factors
Social Selection
? More than 50 studies in US and Europe
? Contends people who cannot make it in
※normal§ society gradually become lower
in SES due to poor coping skills
? May occur across generations
? People with lower SES are diagnosed
more frequently with schizophrenia than
people in middle or upper SES
? Why?
Two theories
? Social Selection Theory
? Increased Stress Theory
?
? Result 每 A whole class of people become
lower SES
? Model points to flaws in the individual
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Psyc 311 每 Abnormal Psychology
Psyc 311 每 Abnormal Psychology
Increased Stress
Conclusions
? Contends there are flaws in society itself
? Focuses on the amount of stress
experienced in different environments
? Many models
? Lots of different ideas
? Some evidence form each
? Not solid for an particular model
? Each have problems.
? Conflicting sides
? Maybe the environment drew in lower
functioning individuals than producing
lower functioning individuals
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