Genetic Explanations Of OCD

Question 1

Genetic explanation

Answer 1

• Predisposition may be inherited
• Information comes from 3 main sources- family studies, twin studies and research methods
• OCD seems to be a polygenic condition

Question 2

COMT Gene

Answer 2

• This gene is associated with the production of an enzyme that regulates the function of dopamine and helps to reduce it’s action
• The variation in the COMT gene decreases the amount of COMT available and therefore dopamine is not controlled, and there is probably too much dopamine (associated with OCD)
• The gene variation is more common in patients with OCD than people without OCD

Question 3

SERT Gene

Answer 3

• The SERT gene affects transport of serotonin, creating lower levels of it. Low levels of serotonin have been implicated with OCD
• The SERT gene appears to be mutated in individuals with OCD
• The mutation causes an increase in transporter proteins at a neuron’s membrane

Question 4

Diathesis-stress model

Answer 4

• This proposes that certain genes leave some people more likely to suffer a mental disorder but it is not certain
• Some environmental stress is necessary to trigger the condition

Question 5

Research to support genes playing a role in OCD (Lewis 1936)

Answer 5

• He observed that of his OCD patients, 37% had parents with OCD and 21% had siblings with OCD
• This suggests that OCD runs in families, however it is probably the vulnerability to the illness that is passed on, not the certainty of OCD

Question 6

Research to support genes playing a role in OCD
(Billett et all 1998)

Answer 6

• This was a meta analysis of 14 twin studies
• On average, MZ twins (identical) were 2 times more likely to develop the disorder than DZ twins (non-identical)

Question 7

Evaluation of genetic explanation for OCD

Answer 7

Caused by genes:
- OCD is polygenic, so no single gene but up to 230 may be responsible
- Drugs that increase serotonin have been shown to reduce OCD symptoms
- Experiments which inject animals with drugs that increase pd levels of dopamine have caused OCD behaviours

Caused by something else:
- Genes do not determine OCD, they only create vulnerabilities. Therefore they are not a direct cause as other factors just trigger the disorder. Support for this comes from twin studies, whereby the concordance rates are not 100%, showing OCD is caused by an interaction with genes and environment
- OCD may be culturally instead of genetically transmitted (e.g based on SLT)
- Family members may be more vulnerable to OCD due to stressful environments rather than because of genetic factors

Question 8

Neural explanations of OCD

Answer 8

• Neural mechanisms refer to regions of the brain, structure and neurotransmitters involved in sending messages through nervous system

Question 9

Decision making systems: Frontal lobes (neural exaltation for OCD)

Answer 9

• The lateral bits of frontal lobe are responsible for decision making and logical reasoning
• Abnormal functioning or damage to this region is linked to OCD, especially conditions like hoarding disorder
• Some cases of OCD, in particular hoarding disorder, are associated with impaired decision making

Question 10

Abnormal brain circuits (neural explanation for OCD)

Answer 10

• The Orbitofrontal cortex (OFC) sends ‘worry signals). These are usually suppressed by the caudate nucleus.
• However, in OCD, the nucleus appear to be damaged, so cannot suppress signals. The caudate nucleus usually filters irrelevant impulses, and only send more powerful ones to the thalamus to take action, however when there is a lack of filtering, the insignificant signals are also acted on (in the form of compulsions)
• Surgery that disconnects basal ganglia from frontal cortex can reduce severe symptoms of OCD

Question 11

Evaluation of neural explanation for OCD

Answer 11

Neural cause:
- The brain of OCD patients are structured and function differently from those of other people. Brain scans of OCD patients reliably show increased activity in the OFC

Not a neural cause:
- Neural hypothesis does not account for Individual differences because the research does not explain why one individual develops OCD while the other develops and different mental disorder, because low serotonin levels are found in other disorders
- CBT (cognitive behavioural therapy) can be very successful treatment and this is difficult to account for in the serotonin hypothesis

Question 12

Evaluation of biological explanation for OCD

Answer 12

Strengths:
- Very scientific method, therefore has high reliability and validity
- Anti-depressants typically work by increasing levels of neurotransmitter serotonin. These drugs are effective in reducing symptoms of OCD and provide support for a neural explanation of OCD

Weaknesses:
- Biological explanations are reductionist as they focus on only one factor and at present our understanding of biochemistry is oversimplified
- Biological explanations are also deterministic because they ignore the individual’s ability to control their own behaviour, which in turn may affect biochemistry levels
- The approach can be criticised for ignoring environmental influences e.g people are not born with OCD, they might learn it from their environment through conditioning