Biological Explanation OF Depression PDF

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BIOLOGICAL EXPLANATIONS OF MOOD DISORDERS 1. BIOCHEMISTRY KEY INFO

STUDY

EVALUATION

Caused by the IMBALANCE in the level of neurotransmitters NORADRENALINE & SEROTONIN in the brain. - LOW levels > depression - HIGH levels > mania Both neurotransmitters affect energy levels, sleep patterns, & hunger and are found in the LIMBIC SYSTEM which controls sleep, appetite &emotions. TRICYCLIC ANTIDEPRESSANTS- block the synaptic reuptake of these neurotransmitters into the presynaptic neuron, increasing their availability. TEUTING -investigated the role of noradrenaline & serotonin in depression. -a compound produced when noradrenaline & serotonin are broken down by enzymes is present in urine. -Teuting analysed & compared urine samples from depressed & non depressed adults RESULTS- Depressed patient’s urine had lower levels of the compound CONC- suggests that depressed people (unipolar) have lower than normal levels of the neurotransmitters in the brain which caused the depression. + Drugs which lower serotonin & noradrenaline bring on depressive states: RESERPINE- lowers the levels of serotonin & noradrenalin in the brain & is known to cause depression  suggests that low levels of serotonin is the cause of depression. + DELEGADO 1990 gave depressed patients, who were receiving antidepressants, a special diet that lowered levels of serotonin. The majority of patients experienced a return to their depressive symptoms, which disappeared again when their diet was normal.  because the special diet lowered levels of serotonin & resulted in depressive symptoms it suggests that low levels of serotonin are the cause of depression. DOES NOT PROVIDE A COMLETE EXPLANATION: - antidepressants immediately raise levels of neurotransmitters but it can take SEVERAL WEEKS for the depressive symptoms to ease. This suggests OTHER FACTORS may be involved in the development of depression e.g. social factors & suggests a MORE COMPLEX INTERACTION between neurotransmitters

2. GENETICS Suggests that we can INHERIT a gene that gives us a GENETIC PREDISPOSITION to developing depression Family and twin studies suggest a genetic basis for depression, with a family history increasing the r of developing the disorder.

FAMILY STUDIES GERSHON reviewed 10 studies of adult unipolar depressed probands & found the rates of depression in 1st degree relatives was between 7-30%- much higher than general pop. TWIN STUDIES MCGUFFIN – UNIPOLAR STUDY Looked at 177 same sex twin pairs, 1 of which had suffered from unipolar depression Concordance rate for MZ twins= 46, Concordance rate DZ twins = 20%. Suggests a genetic predisposition for unipolar depression as c rate for MZ was a lot higher PRICE – BIPOLAR STUDY R- found conc rate of 68% for MZ twins raised together & 67% raised apart & 23% for DZs. CONC- significantly high concordance rate for bipolar depression in MZs suggest a strong genetic predisposition for bipolar depression. As concordance rate is a lot higher for bipolar than unipolar in MZ twins this suggests a stronger role for genetics for depression. PRICEFound significantly high concordance rates for MZs raised together & apart so this rules out the role of the environment- provides strong evidence for a predisposition. + Evidence for a DEPRESSION GENE- WILHELM suggests that an abnormal serotonin transporter gene could play a key role In depression. - Based on INDIRECT EVIDENCE- much evidence requires inference from indirect evidence - Concordance rates NEVER SHOW 100% for MZ twins – cannot say it is a purely genetic disorder or it would be 100 as MZs share 100% of their genetic info. DOES NOT PROVIDE A COMPLETE EXPLANATION - Unipolar depression may not be the result of genetics There is CONTRADICTORY EVIDENCE for the role of genetics in UNIPOLAR depression. BROWN & HARRIS found that other SOCIAL FACTORS such as unemployment, divorce or caring for small children in difficult circumstances may be more important in determining depression.

OVERALL EVALUATION OF THE BIOLOGICAL EXPLANATIONS - NEGLECTS the role of SOCIAL FACTORS e.g. unemployment, divorce, stress, social isolation, family - Biological explanations are REDUCTIONIST – reducing such a complex disorder down to levels of genes or chemicals may be an oversimplification. - they say that biology is only cause of the disorder, it ignores other influences e.g. cognitive, social & environmental factors. HAVE THEY PROVIDED A VIABLE TREATMENT METHOD? + DRUG TREATMENT is the primary course of treatment for both unipolar & bipolar - HOWEVER successful treatment of depression often involves a COMBINATION OF THERAPIES including cognitive as well as drugs. this suggests that there is NOT ONE cause for depression, it may be a result of an INTERATION OF FACTORS e.g. biology, social, cultural....