psychopathology: biological approach to explaining OCD

Question 1

What is the biological approach?

Answer 1

A perspective that emphasises the importance of physical processes in the body such as genetic inheritance and neural function

Question 2

What are the two biological explanations?

Answer 2

Genetic and neural explanations

Question 3

What is the genetic explanation?

Answer 3

• Genes consist of DNA which encodes physical features and psychological features
• Genes are transmitted from parent to child

Question 4

What is the genetic explanation in relation to OCD?

Answer 4

Genes are involved in the individual vulnerability or predisposition to OCD, inherited from parents

Question 5

Where is OCD more likely to occur in?

Answer 5

OCD is more likely to occur in someone who has a parent or sibling with OCD but it may not be clear if genes or the environment are the cause

Question 6

Who conducted research on twin studies?

Answer 6

Nestadt (2010)

Question 7

What did Nestadt find out about twin studies?

Answer 7

• 68% of monozygotic twins had OCD compared to 31% of dizygotic twins
• The higher concordance rate, the more a trait is genetically influenced

Question 8

What other genetics studies are there about OCD?

Answer 8

• Lewis (1936) noticed that of his patients with OCD, 37% had a parent with OCD and 21% had siblings with OCD
• Bellodi et. al (2001) showed that close relatives are more likely to have OCD than distant relatives

Question 9

What have genetic explanations focused on identifying?

Answer 9

Particular genes which are implicated in OCD - referred to as ‘candidate genes’ which influence the functioning of neural systems

Question 10

What are two examples of candidate genes?

Answer 10

The SERT gene and the COMT gene

Question 11

What is the SERT gene?

Answer 11

Also known as the 5-HTT gene and is linked to the neurotransmitter serotonin, affecting reuptake in the serotonin system

Question 12

What is the COMT gene?

Answer 12

Associated with the production and regulation of the neurotransmitter dopamine

Question 13

How can candidate genes lead to having OCD?

Answer 13

Mutations in the COMT or SERT genes may create a vulnerability to developing OCD

Question 14

What is important to consider with genetic explanations?

Answer 14

• Not everyone in a given family gets OCD so there must be additional factors
• What is passed in families is genetic vulnerability not the certainty of OCD
• The diathesis-stress model explains this

Question 15

What does the diathesis-stress model suggest?

Answer 15

That people gain a vulnerability towards OCD through genes but an environmental stressor is also required to trigger the condition. This could be a stressful event, for example bereavements

Question 16

What words describes the genetic nature of OCD?

Answer 16

Polygenic

Question 17

How is OCD polygenic?

Answer 17

A predisposition to OCD is not caused by one single gene but several (may be as many as 230 genes - Tayler (2013))

Question 18

How can there be different types of OCD?

Answer 18

One group of genes may cause OCD in one person but different group of genes may cause the disorder in another person
- described as aetiologically heterogenous -> the origin of OCD has different causes

Question 19

Evaluating genetic explanations: Evidence to support OCD is genetic

Answer 19

• There is clear evidence to suggest a genetic component of OCD e.g. twin studies/ family studies
• With OCD, the more closely genetically related two people are, the higher the cooncordance
• first degree relatives have 10% concordance rates, and dizygotic twins have 31% concordance
• Identical twins share 100% concordance of their genes and have a 68% concordance rate
• This suggests a predisposition to OCD is inherited

Question 20

Evaluating genetic explanations: Environmental risk factors -> limitation

Answer 20

• It is difficult to untangle the effects of environment on genetic factors
• While there is strong evidence that genetic variation can make a person more or less vulnerable to OCD, it does not have an entirely genetic origin
• correlation in family and twin studies does not equal causation
• As the concordance rate for identical twins is 68% and not 100%, the level we would expect for an entirely genetically determined psychological feature, so there must be some role for the environment
• genetic vulnerability only provides a partial explanation for OCD

Question 21

What is the neural explanation?

Answer 21

The view that psychological characteristics are determined by the behaviour of the nervous system, in particular the brain and influence of neurotransmitters and hormones

Question 22

What does the neural explanation focus on the role of?

Answer 22

The role of the neurotransmitter serotonin which regulates mood

Question 23

What are the two main neural explanations?

Answer 23

1) Abnormal/low levels of certain neurotransmitters - specifically low levels of serotonin
2) Certain brain structures and neural circuits may be dysfunctional/abnormal

Question 24

What has neuroimaging techniques enabled researchers to do?

Answer 24

To study the brain in detail and to identify normal brain patterns - this therefore allows comparison with abnormal brain patterns

Question 25

What role does serotonin play in OCD?

Answer 25

Low levels of serotonin are thought to cause obsessive thoughts, and the low level of serotonin is likely due to it being removed from the synapse before it has been able to influence the postsynaptic cell

Question 26

Which regions of the brain do neural explanations focus on?

Answer 26

Basal ganglia and orbito frontal cortex, are said to be implicated in OCD - the thalamus is also involved in OCD

Question 27

What is the basal ganglia?

Answer 27

Includes the stratium and coordinates psychomotor function

Question 28

Who did research into the basal ganglia?

Answer 28

Rapport and Wise (1990) proposed the hypersensitivity of the basal ganglia gives a rise to the repetitive motor behaviours seen in OCD, for example, repetitive washing/cleaning/ checking etc

Question 29

What is the orbito-frontal cortex?

Answer 29

Its functions include decision making - converts sensory information into thoughts and actions

Question 30

What are the functions of the thalamus?

Answer 30

Relaying information to appropriate areas of the brain

Question 31

What do these three regions of the brain together form?

Answer 31

The cortico-stratial-thalamic circuit (the "worry" circuit)

Question 32

What differs in the functioning of these regions for a person with OCD?

Answer 32

In normal functioning, the basal ganglia filters out minor worries coming from the OFC, but if this area is hyperactive, even small worries get to the thalamus

Question 33

What does PET scans suggest about compulsions?

Answer 33

The heightened activity in the orbitofrontal cortex increases the conversion of sensory information to actions (behaviours) which results in compulsions.

Question 34

Evaluating neural explanations: research support -> strength

Answer 34

- Efficacy of drug treatments suggest neural causes of OCD i.e. if increasing levels of serotonin reduces OCD symptoms, low levels of serotonin may have been the cause - Antidepressants that work purely on serotonin are effective in reducing OCD symptoms - Several neuroimagin studies using PET scanners have allowed researchers to investigate specific areas of the brain more accuratey - evidence of dysfunction/abnormality of basal ganglia/OFC in OCD sufferers

Question 35

Evaluation: Correlation and causality -> limitation

Answer 35

- Just because administering SSRIs decreases OCD symptoms, does not mean that this was the cause in the first place - paracetamol paradox - Much of neural evidence is correlational when describing the relationship between neural abnormality and OCD - such correlations do not necessarily indicate a causal relationship - It is possible that OCD that the OCD causes the abnormal brain function or both are influenced by a third factor