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Chapter 2

PSYB32H3 Chapter Notes - Chapter 2: Panic Disorder, Twin Study, Genetic Marker

Course Code
Mark Schmuckler

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B32: Abnormal Psychology
Chapter 2: Current Paradigms & the Role of Cultural Factors
Paradigm- set of basic assumptions, a general perspective, that defines how to conceptualize and study a
subject, how to gather and interpret relevant data, even how to think about a particular subject; the conceptual
framework or approach within which the scientist works.
Paradigms are a set of basic assumptions that outline the particular universe of scientific inquiry.
Paradigms specify what problems scientists will investigate and how they will go about the investigation.
oIt injects inevitable biases into the definition and collection of data and may also affect the
interpretation of facts.
oThere are five paradigms:
Humanistic and existential
Biological paradigm- a broad theoretical view that holds that mental disorders are caused by some abberant
somatic process or defect. Aka ‘medical model or ‘disease model
For a time, the germ theory was the paradigm of medicine, but it soon became apparent that this theory could
not account for all diseases.
Contemporary Approaches to the Biological Paradigm
More sophisticated approaches are used today, and there is now an extensive literature on biological factors
relevant to psychopathology.
Heredity probably predisposes a person to have an increased risk of developing schizo, depression may result
from chemical imbalances within the brain, anxiety disorders may stem from a defect within the autonomic
nervous system that causes a person to be too easily aroused.
There are 3 areas of research within this paradigm, in which the data are particularly interested:
1- behavior genetics
2- molecular genetics
3- biochemistry

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Behaviour Genetics
Chromosomes are made up of thousands of genes, the carriers of the genetic information (DNA) passed from
parents to child.
Beheaviour genetics- the study of individual differences in behaviour that are attributable in part to
differences in genetic makeup.
Genotype- an individuals unobservable, genetic constitution; the totality of genes possessed by an individual.
Phenotype- the totality of observable characteristics of a person.
The phenotype changes over time and is viewed as the product of an interaction between the genotype and the
Any measure of intelligence is best viewed as an index of the phenotype.
It is critical to recognize that various clinical syndromes are disorders of the phenotype, not of the genotype.
oThus it is not correct to speak of the direct inheritance of schizo or anxiety disorders; at most
only the genotypes for these disorders can be inherited
oWhether these genotypes will eventually engender the phenotypic behaviour disorder will
depend on environment and experience.
oA predisposition, also known as a diathesis, may be inherited, but not the disorder itself.
Four basic methods to uncover whether a predisposition for psychopathology is inherited:
1. family method
2. twin method
3. adoptees method
4. linkage analysis
1. – Family Method
family method- a research strategy in behaviour genetics in which the frequency of a trait or of abnormal
behaviour is determined in relatives who have varying percentages of shared genetic background.
On average, siblings as well as parents and their children are identical in 50% of their genetic background.
oPeople who share 50% of their genes with a given individual are called first-degree relatives of
that person.
oNewphews and nieces share 25% of their genetic makeup of an uncle and are called second
degree relatives
The starting point in such investigations is the collection of a sample of individuals who bear the diagnosis in
oThese people are referred to as index cases, or probands.
index cases (probands)- the person who in a genetic investigation bears the diagnosis or trait in which the
investigators are interested.

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2. – Twin Method
twin method- research strategy in behaviour genetics in which concordance rates of monozygotic and
dizygotic twins are compared
monozygotic twins- genetically identical siblings who have developed from a single fertilized egg; always
the same sex; sometimes called ‘identical twins’.
dizygotic twins- birth partners who have developed from separate fertilized eggs and who are only 50% alike
genetically, no more so than siblings born from different pregnancies; sometimes called ‘fraternal twins’.
When the twins are similar diagnostically, they are said to be concordant, to the extent that a predisposition
for a mental disorder can be inherited, concordance for the disorder should be greater in genetically identical
MZ pairs than in DZ pairs.
The ability to offer a genetic interpretation of data from twin studies hinges on what is called the equal
environment assumption.
oThe equal environment assumption is that the environmental factors that are partial causes of
concordance are equally influential for MZ pairs and DZ pairs.
oThe equal environment assumption would assert that MZ pairs and DZ pairs have equivalent
numbers of stressful life experiences.
3. – Adoptee Method
adoptee method- research method that studies children who were adopted and reared completely apart from
their abnormal parents, thereby eliminating the influence of being raised by disordered parents.
If a high frequency of panic disorder were found in children reared apart from parents who also had panic
disorder, we would have support for the theory that a genetic predisposition figures in the disorder.
* this situation occurs so rarely that there is virtually no research using this method to study psychopathology;
used to study personality traits.
Molecular Genetics
molecular genetics tries to specify the particular gene or genes involved and the precise functions of these
Allele- refers to any one of several DNA codings that occupy the same position or location on a chromosome.
oA person’s genotype is his/her set of alleles.
The term “genetic polymorphism refers to the variability among members of the species.
oIt entails mutations in a chromosome that can be induced or naturally occurring.
4. – Linkage Analysis
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