BIOLOGICAL BIOLOGICAL EXPLANATIONSEXPLANATIONS

Bio chemical Bio chemical changeschanges

Genetic inheritance

Metabolic & hormonal changes

MAOI’SMAOI’S• In the 1950’s, using

Monoamine oxidising inhibitors for TB, they discovered that patients were remarkably euphoric

Yippee, I’m ill!

Qu. Qu. Therefore, what Therefore, what neurotransmittersneurotransmitters are likely are likely to be involved with mood?to be involved with mood?

• Monoamines are = ?•Serotonin – Noradrenaline –

Dopamine•

• catecholamine" hypothesis• Schildkraut (1965) believed that too

high a level of noradrenaline led to mania and too little to depression. 

Qu. What happens if you Qu. What happens if you change the level of one change the level of one

monoamine?monoamine?

• Prange, 1974• A deficit in serotonin ‘permits’ (not

causes) the symptoms of depression.• Changes in serotonin levels affect the

nature and intensity of the symptoms.• If monoamine activity is increased =

mania• If monoamine activity is decreased =

depression

Kety, 1975Kety, 1975 – – Permissive Permissive Amine TheoryAmine Theory

• Both Serotonin and noradrenaline levels change in mood disorders.

• It is serotonin that controls the levels of noradrenaline.

• High levels of serotonin keep levels of noradrenaline constant which prevents mood swings.

• There is a serotonin deficit in depressives = is genetic.

• Qu. Therefore, according to this theory, what happens if there are low serotonin levels?

Kety, 1975Kety, 1975 – – Permissive Amine Permissive Amine TheoryTheory

Serotonin

Mania 

Depression

Noradrenaline

Qu. What if Serotonin levels drop to a very low level?

Supporting evidence for Supporting evidence for the permissive amine the permissive amine

theory?theory?

• Teuting et al (1981)

• Examined the urine of depressed patients

• Found by-products that suggest lowered levels of both serotonin and noradrenalin.

Supporting evidence for Supporting evidence for the permissive amine the permissive amine

theory?theory?

• McNeal & Cimbolic (1986)

• Examined the cerebo -spinal fluid of depressed suicidal patients

• Found reduced amount of by-product.

• Suggests low level of serotonin in the brain

Qu. If this theory is true, what would Qu. If this theory is true, what would happen if you take drugs to increase happen if you take drugs to increase

serotoninserotonin levels? levels?

• Drugs treatments that concentrate on raising serotonin levels (SSRI’s) do improve the depressed mood in the majority of patients

• Newer anti-depressants (like Effexor) are actually targeted at both serotonin and noradrenaline, and are even more effective in treating depression.

Qu. Can this theory explain Qu. Can this theory explain gender differences in gender differences in

prevalence rates?prevalence rates?• Diksic et al (1997)

• Found that men make 52% more serotonin than women.

• Qu. Conclusion?• This could make men

far less prone to depression than women.

• 1. Not all depressives show reduced levels of these neurochemicals.

• Qu. Would these benefit from drug treatments?

• No, not all patients benefit from drugs treatments.

• Qu. What does this imply about the causes?

• Are other biological factors involved?• Cortisol, oestrogen, diet?

Qu. Any criticisms of Qu. Any criticisms of theory?theory?

Qu. Any criticisms of Qu. Any criticisms of theory?theory?

• Deakin & Graeff (1991) • 2. Even following recovery from

depression the deficits in serotonin and noradrenalin levels still remain.

• Qu. What does this imply?• Another neurochemical involved

perhaps?

• 3. Anti-depressives such as MAOIs (monoamine oxidase inhibitors) increase the levels of noradrenalin and serotonin within minutes. 

• However, they have no effect on mood for many weeks (normally two weeks).

• This suggests that they are not working simply by increasing the levels of chemical in the brain.

• Qu. What does this imply about the cause?

Qu. Any criticisms of Qu. Any criticisms of theory?theory?

Conclusion:Conclusion:Depressio

n is a complex

issueWe don’t really understand the full interaction

between neurotransmitt

ers. Other biological

factors are clearly

involved.

Genetics & DepressionGenetics & DepressionQu. How do you ‘prove’ a

genetic argument for any behaviour?

Twin studies:

MZ

DZ

McGuffin et al, 1996

46%

20%

Bertelsen 1977

59%

30%

Qu. Problems?

Genetics & DepressionGenetics & DepressionFamily concordance rates

Gen Pop

Gershon 1990

15%

40-50%

Wender 1986

15%

70% if adopted

Qu. Problems?

Family

Essay PreparationEssay Preparation

•Biological Aetiologies• Using PPt and handout group A01

and AO2 material for Neurotransmitter Explanations

• Do the same for genetic explanations