Biological explanations for OCD Flashcards
What is the role of genes?
Specific candidate genes involved in OCD
Polygenic condition
Predisposed
Variation of genes = different types of OCD
What does the term ‘aetiologically heterogeneous’ mean?
Origins of OCD vary from one person to another.
What research suggests that OCD is polygenic condition?
Something swift 🎤
Taylor et al (2003)
230 genes involved in OCD
Describe the COMT gene:
Variation in COMT gene = higher levels of dopamine
Describe the SERT gene:
Affects transport of serotonin
Transportation issues = lower levels of serotonin in the brain
What research supports SERT gene?
Sounds like the fragments of DNA?
Ozaki et al (2003)
Mutation of gene in 2 families –> 6/7 members had OCD.
What does the diathesis stress model conclude to?
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.
Strength of genetic explanation:
Guy sounds like the hot chocolate brand and a martini drink + Nicki Minaj
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
Limitation of genetic explanation for OCD:
risky risky wisky wisky this is an emergency help me Cromer
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
Limitation of genetic explanation:
Alshamiri and hand washing mice
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
What is the role of neurotransmitters on affecting OCD?
Both neurotransmitters seen to have an affect on OCD
Serotonin –>regulates mood
lower levels = mood disorders
Possibly caused by SERT gene
What research supports reduced symptoms when serotonin levels brought backup to optimum?
OINK OINK
Piggott et al (1990)
Antidepressants that reduce serotonin —> reduction in symptoms
Those who do not have it = no effect
(Jenicke, 1992)
What is the issue with low serotonin?
Cause obsessive thoughts
Process of reuptake occuring too quickly
Serotonin doesn’t stay in synapse for long enough to affect mood
Limitation of neuronal explanation:
Two birds with one stone, except one bird is depressed
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.
How does structures of the brain link to OCD?
OCD = abnormal brain circuits in various regions of frontal lobe
Healthy brain structure?
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
How does the worry circuit function in person who has OCD?
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
What is the role of parahippocampal gyrus?
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
Supporting research of abnormal brain structures!
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
Research support
Serotonin with ,
Dopamine with fast n furious
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
