Biological Explanations of depression

Learning objectives:

To outline one Biological explanations of depression

To evaluate one Biological explanations of depression

Biological explanations

of Depression

1.Genetic explanation

2.Neurochemical explanationThe monoamine Hypothesis

family, twin and adoption studies

“carried out an important FAMILY

STUDY into the inheritance of

depression

Genetic explanationThree types of study

conducted TWIN STUDIES which

looked for evidence that depression is

inherited

Elliot S GershonUniversity of Chicago

Peter McGuffinKings College London Paul H Wender

Harvard Medical School

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 …

method of researching the inheritance of

depression is to carry out

ADOPTION STUDIES

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

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 relativesMendlewicz et al (1977)- bi polar- 7% in biological- 0% in adoptive= stronger genetic influence!!

How can you evaluate the research that you have found?

A02

Twins studies

Adoption studies

Family studies

What is the problem of relying on family and twin studies as

support for a genetic explanation of

depression?

Genetic explanationAdoption 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 …

“Adoption studies are an improvement,

because they eliminate the

influence of the family environment

…

What causes depression

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?

Make sure you elaborate your A02……..

Develop your A02 skills……

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.

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

Biological Explanations of depression

Learning objectives:

To outline one Biological explanations of depression

To evaluate one Biological explanations of depression

Biological explanations

of Depression

1.Genetic explanation

2.Neurochemical explanationThe monoamine Hypothesis

family, twin and adoption studies

Recap quiz on genetic explanations of depression

1.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)

2.What did Mcguffin find?(2)3. Identify one problem with Mcguffin’s study(2)4.Which studies (twin, family or adoption) provides

the strongest support for the genetic explanation, explain your reason?(2)

5. Identify one problem with family or adoption studies.(2)

The neurochemical explanation

• Depression is a result of reduced levels of certain neurotransmitters (neuro chemicals), e.g:

• Serotonin

• Noradrenaline

• Dopamine (Monoamines)

Hence, Monoamine hypothesis

Neurotransmitters

monoamines

serotonin

noradrenaline

Dopamine

Who can explain this diagram???

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

Generic essay structure for explanations

Important to Conclude!!

Is the biological explanation a full or complete explanation of depression?

It may be we inherit a genetic predisposition?

Homework • Discuss two or more biological explanations for

depression. In your evaluation you should refer to research evidence (24 marks)