biological approach to explaining OCD Flashcards
what are the 2 explanations?
- genetic explanation
- neural explanation
what are the key details of the genetic explanation?
- inherit genetic vunerability
- candidate genes
- ocd is polygenic
- aetiologically heterogenous
explain genetic vulernability in relation to OCD
individuals have greater vunerability to first degree relatives who have OCD
what is Lewis’ research?
37% OCD patients had parents with OCD. 21% had siblings with OCD
explain candidate genes in relation to OCD
specific genes that could be responsible for OCD. genes are involved with regulating development of serotonin system
how is OCD polygenic ?
its caused by combination of genetic variations to increase vunerability
what is Taylor’s research?
found theres upto 230 different genes that may be involved with OCD
what does the stress- diathesis model suggest?
certain genes leave people more LIKELY to develop mental disorder but not certain. environmental stress triggers condition
explain aetiologically heterogenous in relation to OCD
there are different complex forms of OCD so different genes involved in cause of each type. the origins of OCD vary from one person to another
evaluation points for genetic explainations
S: good supporting evidence
S: evidence from animal studies-
L: could be environmental risk factors
what supporting evidence is there for genetic explanation?
- Nestadt et al from twin studies
- 68% identical twins shared OCD as opposed to 31% non-identical
- must be some genetic influence on development of OCD
- counter- twin studies ungen, twins have same env so reduces value of twin studies
what evidence is there from animal studies to support the genetic explanation?
- particular genes are associated with repetitive behaviour on other species (mice)
- provides evidence to support expl
- however- minds/brains of humans more complex and may not gen to human OCD
- not tell much about human OCD
what environmental risk factors could there be to weaken the genetic explanation?
- OCD not entirely genetic in orgin and env risk factors can trigger/increase risk of developing OCD
- Cromer- over half OCD patients experienced traumatic event in past
- genetic vunernability only provides partial exp
what are the key details of the neural explanation?
- role of neurotransmitters: serotonin
- brain structures
- the worry circuit
explain the role of neurotransmitters
- low levels of serotonin = normal transmission of mood relevant info doesnt take-> mental processes affected.
- some OCD assicoated with reduced levels of serotonin caused by SERT gene
- some OCD explained by reduction in functioning of serotonin system in brain
SERT gene
gene that causes low level of serotonin
explain brain structures
some OCD associated with impaired decision making bc of brain structures:
- lateral frontal lobe
- left parahippocampal gyrus
area responsible for logical thinking + decision making?
Lateral Frontal Lobe
explains obsessive thoughts + compulsions
area responsible for processing unpleasant emotions?
Left Parahippocampal Gyrus
explains disgust, anxiety, guilt
explain the worry circuit
two brain areas associated with OCD:
1- orbit frontal cortex
2- caudate nucleus
orbit frontal cortex
sends worry signals that are picked up by thalamus and directed around body
caudate nucleus
suppresses some of the worry signals
what happens if the caudate nucleus is not working properly?
the worry signals do not get suppressed and a person worries too much which can cause OCD
what is the worry circuit supported by?
PET scans- shows heightened activity in OFC when holding a dirty cloth. PET scans= objective and scientific
evaluation points of neural explanations
S: some supporting evidence- antidepressants + parkinsons disease
L: cause and effect- result of OCD rather than cause- correlation
L: OCD link may be co-morbidity with depression
what supporting evidence is there for neural explanation?
- antidepressants working on serotonin effective to reduce symptoms
- suggests serotonin involved
- OCD symptoms present in other disorders we know have biological basis - Parkinsons
- biological processes underlie OCD + bio factors responsible for OCD
what is the issue with cause and effect for neural explanation?
- evidence to suggest neurotransmitters and structures of brain dont function normally in patients with OCD
- could be a result of OCD rather than cause
- correlational link= no causal relationship
- OCD could cause abnormal brain functions
how is OCD co-morbid with depression?
- many who suffer from OCD become depressed
- depression involved disruption to serotonin
- serotonin activity is disrupted in many with OCD bc they are depressed
- serotonin may not be relevant to OCD symptoms
