Biological explanations for OCD

Question 1

What is the role of genes?

Answer 1

Specific candidate genes involved in OCD

Polygenic condition

Predisposed

Variation of genes = different types of OCD

Question 2

What does the term ‘aetiologically heterogeneous’ mean?

Answer 2

Origins of OCD vary from one person to another.

Question 3

What research suggests that OCD is polygenic condition?

Something swift 🎤

Answer 3

Taylor et al (2003)

230 genes involved in OCD

Question 4

Describe the COMT gene:

Answer 4

Variation in COMT gene = higher levels of dopamine

Question 5

Describe the SERT gene:

Answer 5

Affects transport of serotonin

Transportation issues = lower levels of serotonin in the brain

Question 6

What research supports SERT gene?

Sounds like the fragments of DNA?

Answer 6

Ozaki et al (2003)

Mutation of gene in 2 families –> 6/7 members had OCD.

Question 7

What does the diathesis stress model conclude to?

Answer 7

Highly unlikely 1 gene/combination of genes solely responsible for development of OCD

–> too complex

–>SERT genes present in other disorders.

Produce genetic vulnerability

Triggered by stressor in environment.

Question 8

Strength of genetic explanation:

Guy sounds like the hot chocolate brand and a martini drink + Nicki Minaj

Answer 8

Strong evidence

–>suggests vulnerability to OCD due to genetic make up

Nestadt et al (2010) –> reviewed twin studies:

68% MZ twins = OCD

31% DZ twins = OCD

Family studies
Family member with OCD = 4x more likely compared to someone without (Martini + Stebnicki)

Genetic link

Question 9

Limitation of genetic explanation for OCD:

risky risky wisky wisky this is an emergency help me Cromer

Answer 9

Environmental risk factors

Strong evidence for idea that genetic variation = more/less vulnerable to OCD

Not the case

Cromer et al (2007). –> over half OCD clients = traumatic event in past. OCD more severe with those who have trauma

Diathesis stress model

Partial explanation

Question 10

Limitation of genetic explanation:

Alshamiri and hand washing mice

Answer 10

Hard to find candidate genes –> lots of variations

Evidence from animal studies:

Show particular gene variations are associated with repetitive behaviours (hand-washing)

Suggests genes play role in development of OCD

Human mind> mice mind
More complex so weak explanation –> results not generalisable

Question 11

What is the role of neurotransmitters on affecting OCD?

Answer 11

Both neurotransmitters seen to have an affect on OCD

Serotonin –>regulates mood

lower levels = mood disorders

Possibly caused by SERT gene

Question 12

What research supports reduced symptoms when serotonin levels brought backup to optimum?

OINK OINK

Answer 12

Piggott et al (1990)

Antidepressants that reduce serotonin —> reduction in symptoms

Those who do not have it = no effect
(Jenicke, 1992)

Question 13

What is the issue with low serotonin?

Answer 13

Cause obsessive thoughts

Process of reuptake occuring too quickly

Serotonin doesn’t stay in synapse for long enough to affect mood

Question 14

Limitation of neuronal explanation:

Two birds with one stone, except one bird is depressed

Answer 14

Serotonin- OCD link not unique as said to be

Lots with OCD = Clinical depression

Co-morbidity

Depression also via disruption of serotonin

Leaves us with logical issue

Could be that serotonin activity is disrupted in people with OCD because they are depressed as well.

Question 15

How does structures of the brain link to OCD?

Answer 15

OCD = abnormal brain circuits in various regions of frontal lobe

Question 16

Healthy brain structure?

Answer 16

OFC worries

Caudate nucleus (basal ganglia) supresses signals from OFC + sends back to OFC

OFC sends signals to thalamus about things that are actually worrying

Sends worry signals to body

Question 17

How does the worry circuit function in person who has OCD?

Answer 17

Caudate nucleus = damaged
~~> fails to suppress minor worry signals

Sends all worries to thalamus

Too many worries uwu

Thalamus sends signals back to OFC –> acts as worry circuit

Question 18

What is the role of parahippocampal gyrus?

Answer 18

Processes unpleasant emotions

Damaged = amplify emotional distress –> impairs emotional regulation

Threat perception issues

Limbic system interaction –> abnormal connection with amygdala –> intensify fears

Reinforces maladaptive behaviour cycles

Question 19

Supporting research of abnormal brain structures!

Answer 19

PET scans show heightened activity in OFC of OCD patients

PET = objective + specific data

HOWEVER

–> lack temporal precision

Expensive

Not establish causality between brain activity and ODC symptoms

Question 20

Research support
Serotonin with ,
Dopamine with fast n furious

Answer 20

Sertonin + dopamine linked to frontal lobe

Comer (1998) –> serotonin plays key part in OFC + caudate nuclei.

–> abnormal levels of serotonin cause these parts to malfunction

Sukel (2007) –> dopamine main neurotransmitter in basal ganglia

High levels of dopamine = overactivity in region of brain