BIOLOGICAL EXPLANATIONS

Bio chemical changes Genetic inheritance Metabolic & hormonal changes

MAOI’S MAOI’S In the 1950’s, using Monoamine oxidising inhibitors for TB, they discovered that patients were remarkably euphoric Yippee, I’m ill!

Qu. Therefore, what neurotransmitters are likely 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 change the level of one 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, 1975 – Permissive Amine 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, 1975 – Permissive Amine Theory Serotonin Mania Depression Noradrenaline Qu. What if Serotonin levels drop to a very low level?

Supporting evidence for the permissive amine 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 the permissive amine 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 happen if you take drugs to increase serotonin 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 gender differences in 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 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 theory?

Conclusion: Depression is a complex issue We don’t really understand the full interaction between neurotransmitters. Other biological factors are clearly involved.

Genetics & Depression Qu. How do you ‘prove’ a genetic argument for any behaviour? Twin studies: MZ DZ McGuffin et al, % 20% Bertelsen % 30% Qu. Problems?

Genetics & Depression Family concordance rates Gen Pop Gershon % 40-50% Wender % 70% if adopted Qu. Problems? Family

Essay Preparation Biological Aetiologies Using PPt and handout group A01 and AO2 material for Neurotransmitter Explanations Do the same for genetic explanations