Models of Abnormal behavior
Naomi Wagner, PhD
Categories of Explanations of Abnormal
Behavior
• Biological: genetics, brain anatomy,
biochemical imbalance, central nervous
system, etc
• Psychological: Emotions, thoughts.
Personality, learning
• Social: issues with relationships
• Sociocultural: norms for behavior,
expectations, cultural climate
What is a Model?
• Etiology:
– Cause or origin of a disorder
• Model:
– An analogy used by scientists, usually to
describe or explain a phenomenon or process
they cannot directly observe
– Model, viewpoint, and perspective are often
used interchangeably
Models (cont-d)
• These one-dimensional views are overly
simplistic:
– Set up a false “either-or” dichotomy between
nature and nurture
– Fail to recognize the reciprocal influences of
one on the other
– Mask the importance of acknowledging the
contributions of all four dimensions in the
origin of mental disorders
The Biopsychosocial Model
• Interaction between the possible causes
• Multiple pathways to any disorder
• Not all causes contribute equally to a
disorder
• People exposed to the same factors may
not develop the same disorder
• People exposed to different factors may
develop similar disorders
The Structure of the nervous System
The Structure of the Nervous system
• The Central Nervous System: The brain
and spinal cord
• The Peripheral Nervous System:
• A. The Somatic NS
• B. The Autonomic NS (sympathetic and
para-sympathetic.)
Neural Transmission
How is information transmitted in the brain
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Neurons are separated by a gap (synapse)
The neurons “communicate” at the synapse
Neuron structure: dendrite, cell-body, axon
Electrical signals are transmitted chemically
across the synapse
The signals stimulate the “pockets” at the tip of
the axon to release neurotransmitter
Cont-d
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Electro- chemical transmission
The signal stimulates the vesicles
Vesicles release the neurotransmitter into the synapse
Neurotransmitter: Chemical substance released from
a neuron into the synaptic cleft it drifts across the
synapse and is absorbed by the receiving neuron
• The signal “floats” on the neurotransmitter to the next
neuron
• Neurons form inter-connected pathways
Cont-d
• The neurotransmitters can either excite or inhibit
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the neuron receiving the signal
The activity of the neuron depends on the
balance between “on” and “off” signals
Serotonin is implicated in depression and the
OCD.
Dopamine is implicated in schizophrenia (too
much) and Parkinson (too little)
GABA (an inhibitory) is implicated in anxiety
Biochemical Theories
• Basic premise:
– Chemical imbalances underlie mental
disorders
• Dendrites:
– Receive signals from other neurons
• Axons:
– Send signals to other neurons
Neural Transmission
Selected Neurotransmitters Involved in
Some Mental Disorders
Abnormalities in Brain Structure
• It is not always possible to connect brain
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structures to psychological symptoms
researchers believe that abnormally developed
brain structures
In 1848 an explosion during the paving of a rail
road caused a metal rod to pierce Phineas Gage
eye socket and to enter his brain
As a result he showed significant changes in
personality
The Human Brain
Functions of the brain
• The forebrain:
– Controls all the higher mental functions, such
as learning, speech, thought, and memory
– Thalamus:
• “Relay station;” transmits nerve impulses
throughout brain
– Hypothalamus:
• Regulates bodily drives and body conditions
– Limbic system:
• Involves experiencing and expressing emotions
and motivation
Cont-d
• The midbrain:
– Involved in vision and hearing, and along with
the hindbrain, controls sleep, alertness, and
pain
– Manufactures serotonin, norepinephrine, and
dopamine
• The hindbrain:
– Controls heart rate, sleep, and respiration
– Manufactures serotonin
Genetic Influences
• Each cell of our body contains 46 chromosomes
• They are made of DNA our genetic material
• A gene is a segment of DNA along the length of
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the chromosome that contain the instructions for
forming proteins which in turn determine how
the cell works
Proteins are the building blocks of our body
Human Chromosomes
Genetics (cont-d)
– Genetic abnormalities can come about through:
• Inheritance of particular combinations of genes
• Faulty copying when cells reproduce
• Mutations that a person acquires over the course
of life
• Cells possess the ability to repair many of the
mutations
• The 46 chromosomes are arranged in 23 pairs
• One chromosome from mother and one from
father
Genetics (cont-d)
• Genetic makeup plays an important role in
developing abnormal conditions
• Autonomic nervous system reactivity may
be inherited
• Hereditary factors are implicated in
alcoholism, schizophrenia, and depression
What do genes do?
• Genes control the manufacturing of
neurotransmitters as well as the way the
neurotransmitters behave at the synapse
• Genes also determine how the brain
structures develop throughout life
• Any factor that can alter the genetic code
can alter how those structures perform
Genotype and Phenotype
• The 46 chromosomes are arranged in 23 pairs
• Twenty-two of the pairs are identical (the 23rd
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pair is the sex chromosomes XX and XY )
It means that the same gene is located in the
same place on each of the chromosomes
Two forms of the same gene are called alleles
The Genotype is the overall genetic makeup
The Phenotype is the expression in your
physique and psychological attributes
Dominant Recessive Relationship
• The Alleles are related to each other in
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Dominant- Recessive relationship
a dominant allele prevails over a recessive allele
However, human characteristic and
psychological disorders are polygenic- more than
one gene participates in determining a given
characteristic
Epigenetics is the attempt to understand how
the environment affects genes to produce
genotypes
PATTERN OF DOMINANT-RECESSIVE TRAIT
INHERITANCE
Genes-environment Interactions
– Interactions between genes and the
environment
– Passive exposure: Children are exposed to
environments that their parents create based
on the parents’ genetic predisposition
– The child’s genetically- based traits elicits
responses from the environment
– Niche-Picking: the child seeks out an
environment that gratifies his/her geneticallybased inclinations
Diathesis-Stress Model
• Proposal that people are born with a
predisposition that places them at risk for
developing a psychological disorder if
exposed to certain extremely stressful life
experiences.
Assessment of Genetic Factors
– Family inheritance studies: Researchers
compare the disorder rates across relatives
who have varying degrees of genetic
relatedness
– Usually comparing Identical twins who share
100% of their genes to Fraternal twins who
share 50% of their genes
– Studies comparing parents and children are
confounded because of possible
environmental effect
Biologically- Based Therapies
• Psychopharmacology:
– Study of effect of drugs on mind and behavior
• Electroconvulsive therapy:
– Application of electric voltage to the brain to
induce convulsions
• Psychosurgery:
– Brain surgery for the purpose of correcting a
severe mental disorder