biological explanation of OCD

Question 1

Genetic explanation def

Answer 1

Genes make up chromosomes and consist of DNA which codes the physical / psychological features of an organism.

Question 2

Genetic explanation overview

Answer 2

Genes involved in individual vulnerability to OCD
Lewis observed that of his OCD patients
* 37% had parents with OCD
* 21% had siblings with OCD
Suggesting that OCD runs in the family → genetic vulnerability more likely not certainty of OCD

Question 3

Diathesis stress model

Answer 3

according to this certain genes leave people more likely to suffer a mental disorder ( not certain) → environmental stress is necessary to trigger the condition. VULNERABILITY
* The condition itself does not manifest until this vulnerability is triggered by a stressor

Question 4

What are candidate genes?

Answer 4

genes that generate vulnerability for OCD

Question 5

Cadidate genes examples (3)

Answer 5

5HT1-D beta - regulates serotonin between neurons

SERT gene - regulates serotonin / SERT mutation - low serotonin –> OCD

COMT - regulates dopamine COMT mutation - high dopamine OCD

Question 6

what does OCD being polygenic mean?

Answer 6

Not caused by one gene but serveral are involved

Question 7

How many genes are involved to be involved within OCD?

found by Taylor

Answer 7

230 genes

Question 8

Different types of OCD

What does aetiologically heterogeneous mean?

Answer 8

One group of genes may cause OCD in one person but a whole different set in another person.

(Origin ( aetiology) of OCD has different causes ( heterogeneous)

• Some evidence to support that different types of OCD may be the result of particular genetic variations e.g religious obsession

Question 9

Strengths - genetic explanation

Answer 9

Research support
Evidence that vulnerable to OCD →
Nestadt - reviewed previous twin studies and found that 68% of identical twins shared OCD as oppose to 31% non-identical
twins → ID higher than non ID
strong support for genetic influence within OCD

Utility
Knowing your at risk → allows for making of lifestyle choices

Question 10

Genetic explanation - Limitations

Answer 10

As identical twins concordance was not 100% ( though are 100% similar) → not completely biologic other factors involved / ON balance - partial explanation

Too many candidate genes involved ( 230) → therefore only increases risk of OCD by a fraction
Genetic explanations - little predictive value / genes can be linked to other conditions so not sure if OCD

Environmental risk factors
Cromer - found that over half of the patients with OCD had a traumatic past event → OCD more intense in those with more than one trauma
OCD cannot be entirely genetic in origin - may be more productive to focus on environmental

Question 11

What are neural explanations ?

Answer 11

The genes associated with OCD are likely to affect the levels of key neurotransmitters as well as structures of the brain.

Question 12

Role of serotonin in OCD

Answer 12

• Involves the role of neurotransmitters serotonin → believed to regulate mood

If a person has low serotonin - normal transmission of mood-relevant information does not take place → mood and obsessions

Some cases of OCD may be explained by a reduction in functioning of the serotonin system in the brain

Question 13

Role of dopamine

Answer 13

controls motivation

High dopamine → motivation → compulsion

Question 14

Decision making systems

Answer 14

• May be associated with abnormal functioning of the lateral of the frontal lobes in the brain
• Frontal lobes → responsible for logical thinking and decision making

Also evidence to suggest the left parahippocampal gyrus associated with processing unpleasant emotions, functions abnormally in OCD

Question 15

What is the worry circuit ?

Answer 15

OFC - orbitofrontal cortex → sends signals to the thalamus about things that are worrying or threatening ( obsessions)
Blocking not strong enough
Signals to strong

Caudate nucleus → inhibits signals from the OFC
If worry signal gets to the thalamus - is alerted which in turns sends signals back to the OFC ( reinforcing worry so acted on) COMPULSIONS

Therefore,OCD may be linked with :
CN underactivity ( fails to suppress worry signals) and / or OFC overactivity ( stronger signals)

Question 16

Strengths - neural explanation

Answer 16

Supporting evidence
Evidence for the role of some neural mechanisms in OCD
Some antidepressants work solely on the serotonin system increasing levels of this neurotransmitter
→ these drugs effective in reducing OCD symptoms
Suggesting serotonin is involved

Studies on decision making have shown that these neural systems are the same systems that function abnormally in OCD

Evidence to suggest that various neurotransmitters and structures of the brain do not function normally in patients with OCD

Question 17

Neural explanations - Limitations

Answer 17

Drugs not 100% effective so
Not just neurotransmitters - other factors play a role
although shows support → only a partial exp..

OCD forms as part of a number of other conditions bio in origin
e.g parkinson disease
Biological processes that cause the symptoms in those conditions may also be responsible for OCD

Not assume the neural mechanisms cause OCD
However, research has also identified other brain systems that may be involved sometimes but no system has been found that always plays a role in OCD
Not able to fully claim to understand neural mechanisms

Not clear what mechanisms are involved
However this is not the same as saying this abnormal functioning causes OCD → biological abnormalities could be a result of ocd

Many people who suffer with OCD become depressed - co-morbidity ( 2 disorders)
This depression involves disruption to serotonin system
Leaves us with a logical problem when comes to serotonin system as an explanation for OCD
Could simply be that the serotonin system is disrupted in many patients who have OCD because they are depressed