Biological Explanations for Major Depressive Disorder

Define aetiology.

The study of the causes or origins of a disease or condition.

What are two main biological explanations for depression?

Genetic factors and neurochemistry.

Define reductionist approach.

Explaining complex behaviour by reducing it to a single factor or cause.

Define holistic approach.

Explaining complex behaviour by considering multiple interacting factors.

What do genetic arguments propose about depression?

That genetic predisposition partly explains vulnerability to depression.

State one strength of genetic research on depression.

Twin studies have shown highly reliable results.

State another strength of modern genetic research.

Large sample sizes now allow identification of specific genetic variations.

How has modern research moved beyond reductionism in genetics?

It recognises the interaction between biological and environmental factors.

State one limitation of genetic research on depression regarding causation.

Studies are correlational and cannot establish cause and effect.

State one limitation of genetic research on depression regarding generalisation.

Twin samples may lack population validity for the general population.

Why is isolating variables difficult in twin studies?

Social and environmental factors are often shared between twins.

Why may genetic arguments be culturally limited?

They do not account for variations in symptoms across cultures.

What is unclear about genetic markers in depression?

How they interact with one another to influence symptoms.

What is the Serotonin Hypothesis?

It proposes that a reduction in serotonin levels increases vulnerability to depression.

What behaviours are linked to low serotonin levels?

OCD-like symptoms, mood swings, worrying, insomnia, and sadness.

What weakens support for the Serotonin Hypothesis?

Many depressed patients do not respond to antidepressants or develop depression without serotonin reduction.

Why does serotonin research suggest bidirectional ambiguity?

Serotonin levels rise quickly with treatment, but improvement takes longer.

What actions do SSRIs have beyond serotonin release?

They increase communication involving serotonin, dopamine, and norepinephrine, promoting neurogenesis and gene expression.

(+) What supports these theories?

Several longitudinal case studies and animal research.

(+) Give another strength of biological explanations for depression.

They have led to effective drug treatments for many patients.

(+) Why can biological studies not confirm causation?

Correlation does not establish direction of effect (bidirectional ambiguity).

(+) Define the Treatment Aetiology Fallacy.

Assuming that if a treatment works, it reveals the disorder’s true cause.

(+) What do biological explanations fail to account for in depression?

Cultural and cognitive variations in symptoms and experiences.