chapter 11 aetiology of psychiatry

8/14/2019 Chapter 11 Aetiology of Psychiatry

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Aetiology of Abnormal Psychology


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Overview

Objective

First :clinical work, try to discover the cause of themental disorders

Second: in seeking a wide understanding ofpsychiatry, from clinical studies, community

surveys, or laboratory investigationsThe complexity of causes in psychiatryby two problems

The first problem is that causes are often remote in

time from the effectsThe second problem is that a single cause may

lead to several effects. Conversely, a single effectmay arise from several different individuals, or bymultiple causes


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Overview

An approach to etiology

Biological factors, psychological

factors and social factors Biopsychosocial perspective


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The classification of causes in

temporal dimension

To divide causes chronologically intopredisposing, precipitating, and perpetuating(maintaining)

Predisposing factors

from early life; in infancy and childhoodThese are factors, many of them operating from

early life, that determine a persons vulnerabilityto causes acting close to the time of the illness.

They include genetic endowment and theenvironment in utero, as well as physical,psychological, and social factors in infancy andchildhood.


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The classification of causes in temporal

dimension

Precipitating factors

Events that occur shortly before the onset of adisorder and appear to have induced it .

They may be physical, psychological, or social. Physicalprecipitating factors include, for example, cerebraltumours or drugs. Psychological and socialprecipitants include personal misfortunes such as the

loss of a job, and changes in the routine of life such asmoving home. Sometimes the same factor can act inmore than one way; for example a head injury caninduce psychological disorder either through physicalchanges in the brain or through its stressfulimplications to the patient.


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The classification of causes in

temporal dimension

Perpetuating factors

Prolong the course of a disorder after it

has been provoked


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The interweaving of temporal and

biopsychosocial factors


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Refugee statusConflict withothers

Poor sanitation

Demands at

work

Bad marriageMalnutritionPerpetuating

Stock-marketloss

Being jiltedIllicit drugs

Being robbedExam failureInfections

RetirementBereavementTraumaPrecipitating

MigrationPersonality

traits

Maternal health

in pregnancy

PovertyParental strifeMothers

alcoholism

Cultural

demands

UpbringingGenesPredisposing

SocialPsychologicalBiological


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Methodological approaches

GeneticsBiochemical studies

Brain-imaging methods

PsychopharmacologyEndocrinology

Neuropathology

ElectrophysiologyPsychology

Sociology


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Genetics

Population genetics (epidemiologicalstudy)

Cytogenetics and molecular genetic

Population genetics

Family risk studies

Twin studies

Adoption studies

Mode of inheritance


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Genetics

Family risk studies:

The results of family studies

The risk of Schizophrenia.

Schizoaffective disorder, andschizotypal personality is increased infirst-degree relatives of patients withSchizophrenia.

The risk of both Schizophrenia andmood disorder is increased in first-degree relatives of patients withschizoaffective disorder.

The risk of bipolar illness is not


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Genetics

Twin studies

The results of twin studies

concordance rates among MZ pairsis higher than that amongcontrol(35-60 times)

concordance rates are about 50%

for MZ and about 10% for DZ. Itmight be expected that someenvironmental factors relevant toetiology.


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14.039/27865.095/146

17.30/5258.332/55Bertelsen(1979)

0.00/3433.35/15Allen et al (1974)

5.02/4066.710/15Harvald and

Hauge(1965)

23.615/5592.625/27Kallman(1954)

23.54/1757.14/7Slater(1953)

16.411/6769.616/23Rosanoff et

al(1935)

0.00/1375.03/4Luxenberger(193

0)

(%) /(%)

/


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Genetics

Adoption studies

The results of adoption studies

The rate for Schizophrenia is greateramong the biological relatives of the

Schizophrenia Adoptees than amongthe relatives of control.

The finding supports the genetichypothesis.

31% 2%


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Genetics

Mode of inheritance

The mode of inheritance is not simple :

dominant, recessive, sex-linked

polygenic inheritance


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Biochemical studies Biochemical studies in psychiatry are difficult to

carry out for three main reasons

1. The living brain is inaccessible to direct study andpost-mortem tissue is not often available

2. Animal studies are of limited use because thereare no obvious parallels in animals to the mental

disorders found in man. 3. It is difficult to prove that any biochemical

abnormalities detected are causal and not secondaryeither to changes in diet or in activity induced by themental disorder, or to the effects of drugs used in

treatment. In schizophrenia, the density of dopamine receptors

is increased

In severe affective disorder, some studies have

found reduced 5-HT (serotonin) function


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Brain-imaging methods

More recently, brain-imaging methods

have been used to study biochemical

function in living brain tissue

Structural imaging techniques

Functional imaging techniques


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PTSD=15. Victims without PTSD=12) 1.

1= (B),2= (C).3= (D),


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fMR I

PTSD


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PTSD

Non-PTSD PTSD

str oo p


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Psychopharmacology

If a drug alleviates a disorder, and if the

mode of action of the drug is known,

then it might be possible to infer the

biochemical abnormality underlying thedisorder


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DST


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Neuropathology

Post-mortem brain studies have been

carried out for over a century, yielding

useful information about dementias

and other organic disorders

organic disorders Vs functional

psychoses


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Electrophysiology

Electrophysiological recordings made

with electrodes on the skull surface (as

in electroencephalography) do not give

precise information about the nature andsite of abnormal brain activity and have

contributed little to the understanding of

psychiatric disorders, except for thoserelated to epilepsy

P h l


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Psychology

Learning theory

Classic conditioning :Learning throughassociation explains, for example, thedevelopment of situational anxiety in phobicpatients following an initial attack of anxietyin the situation. Swallow; saliva

Operant conditioning: The reinforcement of

behaviour by its consequences explains, forexample, the maintenance of disruptivebehaviour in some patients by the extraattention that is provided by staff or

relatives when this behaviour occurs.


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Psychology

Coping mechanisms

Personality factorsBleuler(1911) commented on the

frequency of abnormalities ofpersonality preceding the onset of

schizophrenia.Kretschmer(1936) suggested a

continuous variation between normalpersonality ,schizoid personality, andschizophrenia.

Current finding suggest that theschizophrenia illness may share acommon diathesis with schizotypalpersonality and some related

personality disorder.


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Psycho-social factors

Stress-diathesis mode

Stress

Life events


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Peaceful

time


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Whats stress:

Hostage event of Moscow

more than 200 hostages


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Whats stress:

Airplane accident

ar qua e o


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ar qua e o

Tangshan

160,000 death 240,000

invalid


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. 11


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War


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SARS


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Sociology

Sick role

Social class

Life events

Culture

Migration


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Sociology

Social class :Status within society, determined

usually on the basis of job or income. There is anassociation between schizophrenia and low social

class . Life event A stressful aspect of living that may

be associated with changes in health status.

Life events:have been shown to contribute to the

onset and maintenance of schizophrenia, affective

disorder, and some other psychiatric disorders.

Migration :Movement between societies. Migrationcan be a stressful experience and it has been

suggested as a cause of mental disorder.


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(Koro)


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chapter 11 aetiology of psychiatry

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