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Biological Explanations of depression

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1 Biological Explanations of depression
Learning objectives: To outline one Biological explanations of depression To evaluate one Biological explanations of depression

2 Biological explanations of Depression 1.Genetic explanation
family, twin and adoption studies Biological explanations of Depression 2.Neurochemical explanation The monoamine Hypothesis

3 Genetic explanation Three types of study Peter McGuffin
Aside from saying that there could be a genetic basis for MDD, there isn’t a lot you can say about the actual theory – no single gene has been identified. Therefore, AO1 marks for this explanation are earned by describing the research findings that support a genetic link … Three types of study “carried out an important FAMILY STUDY into the inheritance of depression Elliot S Gershon University of Chicago conducted TWIN STUDIES which looked for evidence that depression is inherited method of researching the inheritance of depression is to carry out ADOPTION STUDIES Peter McGuffin Kings College London Paul H Wender Harvard Medical School

4 Down to you... using Cardwell....
1.Find research evidence for a family, twin and adoption study. 2. You must summarise each piece of evidence. Focus on the results! 3. Explain how the study supports the genetic explanation of depression

5 Evidence for genetic explanations
study Evidence Family Gershon (1990)- rates of MDD in 1st degree relatives= 7-30%, higher than population Oruc (1998)- 3X more likely to be diagnosed with depression if have a first degree relative with depression. Weissmann et al (1984)- relatives of people diagnosed b4 20 had 8x greater chance of being diagnosed than relatives of non-depressed Twin Mcguffin (1996)- 46% concordance rate for MZ, 20% DZ Allen (1976)- MDD, 40% MZ, 11% DZ. Adoption Wendler (1986)- biological relatives 8x likely to have depression compared to adoptive relatives Mendlewicz et al (1977)- bi polar- 7% in biological- 0% in adoptive= stronger genetic influence!!

6 How can you evaluate the research that you have found?
Twins studies A02 Family studies Adoption studies

7 What is the problem of relying on family and twin studies as support for a genetic explanation of depression?

8 Genetic explanation Adoption studies Wender
“I looked at adoption studies, because when a child is adopted, it is taken away from its home and family environment … “Family studies like Gershon’s, and twin studies like McGuffin’s, can’t say genes are the only reason for depression, because they didn’t separate genes from environment … What causes depression “Adoption studies are an improvement, because they eliminate the influence of the family environment …

9 More Evaluation??? Twin and family studies do not consider environmental factors in depression, the higher concordance rate may be due to their shared environment not shared genetics Genetics as a risk factor but depression cant be entirely down to genetics - not 100% concordance rate. What does this suggest? In twin studies- possibility of researcher may be bias, assume that second twin has depression without thorough consideration. Why is this a problem? Sullivan (2000) Few adoption studies have been carried out and those that have such small sample sizes. Why is this a problem?

10 Make sure you elaborate your A02……..
Develop your A02 skills……

11 Possible paragraph layout: Present your evidence What does this evidence suggest Question your evidence, is it strong evidence or are there problems? This matters because Support for the Biological approach to depression comes from twin studies that have looked at the concordance rate of depression between monozygotic and diyzygotic twins. Twins studies allows us to look at how depression has developed in twins that share 100% of their genes in comparison to twins that only share 50%. McGuffin et al (1996) found a 46 % concordance rate with MZ twins in comparison to a 20% concordance rate with DZ twins. A higher concordance rate in MZ twins suggest that the similarities in genes has played a role in the development of depression. However, we should be cautious when using twin studies as evidence because most twins (especially identical) have been brought up in the same environment with the same experiences, so this could play a role in the development of depression. Therefore it may be their shared environment which explains the higher concordance rate (not their shared genes). Furthermore, if the development of depression was solely genetic then we would expect to see a concordance rate closer to 100% in identical twins as the have exactly the same genes, 46% suggests that genes may be a risk factor but that the environment also plays a role. For example, it may be that one twin experiences a trauma that the other twin does not which may lead to only 1 twin developing depression. The idea that depression has a biological basis matters because it allows us to consider the role that genes play in the development and treatment of this mood disorder. For example, the genetic explanations could have implications for further research such as gene therapy.

12 Task Using the paragraph layout, write your own ‘big mac’ paragraph on either family or adoption studies. Bring in other evaluation points, do not use the evaluation points on the example

13 Biological Explanations of depression
Learning objectives: To outline one Biological explanations of depression To evaluate one Biological explanations of depression

14 Biological explanations of Depression 1.Genetic explanation
family, twin and adoption studies Biological explanations of Depression 2.Neurochemical explanation The monoamine Hypothesis

15 Recap quiz on genetic explanations of depression
Mcguffin carried out a twin study looking at concordance rates in depression between MZ and DZ twins. What do we mean by concordance rates?(1) What did Mcguffin find?(2) Identify one problem with Mcguffin’s study(2) Which studies (twin, family or adoption) provides the strongest support for the genetic explanation, explain your reason?(2) Identify one problem with family or adoption studies.(2)

16 The neurochemical explanation
Depression is a result of reduced levels of certain neurotransmitters (neuro chemicals), e.g: Serotonin Noradrenaline Dopamine Serotonin is said to have a calming effect on the brain as it inhibits neural firings. Low levels of the neurotransmitter serotonin lead to depression as this calming effect is not present and mood becomes unstable as other neurotransmitters are not being regulated. Noradrenaline is a neurotransmitter released during in the sympathetic branch of the nervous system ( and in the body’s initial stress response). It increases heart rate and blood pressure. Low levels of this neurotransmitter cause issues such as drowsiness, lethargy and problems with concentration which are symptoms often reported by those suffering from depression. Wender & Klein administered a drug to non-human animals which reduced the levels of noradrenaline produced… The animals became sluggish and inactive, showing symptoms associated with depression. symptoms alone: not necessarily actual depression inferring how animals feel from their behaviour species specific: maybe not generalizable to the entire, human population (Monoamines) Hence, Monoamine hypothesis

17 Who can explain this diagram???
Neurotransmitters monoamines serotonin Dopamine noradrenaline Who can explain this diagram???

18 Biochemical explanations of Depression
Using your text book, answer the questions on the worksheet – all A02 Evaluation points are provided, your job is to explain and extend on them Biochemical explanations of Depression

19 Generic essay structure for explanations

20 Important to Conclude!! Is the biological explanation a full or complete explanation of depression? It may be we inherit a genetic predisposition?

21 Homework Discuss two or more biological explanations for depression. In your evaluation you should refer to research evidence (24 marks)

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