Biological Explanations Flashcards
Gershon
Incidence of depression 3x higher in families with a history of the disorder than general population
Twin studies
Allen - mean concordance of 40% monozygotic (identical) and 11% with dizygotic suggesting unipolar depression is caused by genes
HOWEVER only partial explanation as concordance is never 100%
Adoption studies
Wender et al studied biological relatives of adopted people who had been hospitalised for severe depression. Much higher incidence of severe depression in relatives suggesting genetic makeup is the cause and not environment
Cortisol hypersecretion
Unipolar depressed people have high levels of cortisol which can lead to depressive symptoms. If levels are lowered by means of drugs depression lifts
Strength of cortisol hypersecretion
Memeroff showed there is an increase in adrenal gland (which releases cortisol) in depressed people compared with control group
Weakness of cortisol hypersecretion
Strickland found no evidence of increased levels of cortisol in a large group of women (GENDER BIAS) but did find high levels in non depressed stressed people suggesting that high cortisol levels doesn’t mean you are depressed
Serotonin + study
Low levels can lead to depression. Kety believed fluctuations in noradrenalin levels affects our mood. High levels - mania, low - depression
Supporting studies of serotonin
Rosen - serotonin levels present in large amounts in depressed patients urine
Delgado - placed patients on diet that lowered levels of trytophan (a precursor of serotonin) and found that depressive symptoms returned. However non depressed people experienced no symptoms
Noradrenaline
Low levels of noradrenaline found in depressed patients urine
Correlation
Weaknesses of biological explanations
Individual differences - not everyone benefits from serotonin based
Is low serotonin a result or cause?
Small sample sizes low external validity
Deterministic - biological make up
Reductionist - ignores psychological factors
