Approaches to aetiology in psychiatry

Approaches to aetiology in psychiatry

Dr. Safeya Alchalabi

The complexity of causes in psychiatry

Lack of temporal association
Cause and effect
Indirect mechanisms

The classification of causes

Predisposing factors
Precipitating factors
Maintaining factors (perpetuating factors)

Aetiological models

Reductionist and non-reductionist models
The neuroscience approach
Medical models
The behavioural model
Developmental models
Political models (‘antipsychiatry’, ‘critical psychiatry’)


The neuroscience approach
● All mental processes derive from operations of the brain. Thus all behavioural disorders are ultimately disturbances of brain function, even where the original ‘cause’ is clearly environmental.

The neuroscience approach

● Genes have important effects on brain function and therefore exert significant control over behaviour.

The neuroscience approach

● Social and behavioural factors exert their effects on the brain in part through changes in gene expression. Changes in gene expression leading to altered patterns of synaptic connectivity underlie the ability of experiences to produce learning and psychotherapy to change behaviour.

Genetics

Most psychiatric disorders have a genetic contribution

The genetic contribution to psychiatric disorders

Family studies
Adoption studies
Twin studies

Heritability

Heritability is a measure of the extent to which a phenotype is ‘genetic’.

Epigenetics

Epigenetics describes chemical modifications of DNA and of its binding proteins (called histones), which regulate gene activity without changing the DNA sequence.


Biochemical studies
Biochemical studies can be directed either to the causes of diseases or to the
mechanisms by which disease produces its effects.

Biochemical studies

Post-mortem studies
Brain biochemistry and brain imaging
Peripheral measures (CSF, blood, serum, urine, skin)

Pharmacology

The study of effective treatment of disease can often throw light on
aetiology.

Endocrinology

Changes in circulating concentrations of hormones can have profound effects on mood and behaviour,
abnormalities in endocrine function are responsible for a number of well-defined clinical syndromes, some of which have characteristic neuropsychiatric presentations (e.g. depression in Cushing’s disease).
The onset of puberty is associated with a sharp increase in rates of anxiety and depression.

Physiology

● Psychophysiological methods, including measurements of pulse rate, blood pressure, blood flow, skin conductance, and muscle activity.
● Measurement of cerebral blood flow, metabolism, and neuronalfunction
● Electroencephalographic (EEG) studies.

Thank you