biological approach to explaining OCD Flashcards
2 types of biological explanations for OCD
- genetic explanations
- neural explanations
what are genes involved in
individual vulnerability to OCD
genetic explanation for OCD: study by lewis (1936)
- observed OCD patients
- 37% had parents with OCD
- 21% had siblings with OCD
- suggests OCD runs in families, although what’s probably passed on is genetic vulnerability to OCD not certainty of it
diathesis-stress model & OCD
- certain genes leave some people more likely to develop mental disorder but it’s not certain
- environmental stress required to trigger it
candidate genes & OCD
- include example
- identified genes which create vulnerability for OCD = candidate genes
- some are involved in regulating development of seretonin system
- eg. gene 5HT1-D beta is implicated in transport of seretonin across synapses
what does it mean if OCD is polygenic
OCD isn’t caused by 1 single gene but combination of genetic variations which together increase vulnerability
research on polygenic nature of OCD
taylor (2013)
- analysed findings from previous studies
- found evidence that up to 230 different genes may be involved in OCD
- genes studied in relation to OCD include those associated with action of dopamine & seretonin (both regulate mood)
different types of OCD
- 1 group of genes may cause OCD in 1 person but other group of gene causes disorder in another = aetiologically heterogenous
- also evidence to suggests different types of OCD may be result of certain gene variations (eg. hoarding disorder, religious obsession)
genetic explanations for OCD AO3 +) strong evidence base
E:
- evidence from many source to strongly suggest some people are vulnerable to OCD due to genetic make-up
- (twin studies) nestadt et al. (2010) reviewed twin studies & found 68% of MZ twins shared OCD versus 31% of DZ twins
- (family studies) marini & stebnicki (2012) found someone with a family member diagnosed with OCD is around 4x as likely to develop it as someone without
T: this research suggests there must be some genetic influence in development of OCD
genetic explanations for OCD AO3 -) there are also environmental risk factors
E:
- strong evidence for idea that genetic variation can make someone more/less vulnerable to OCD
- however, OCD doesnt appear to be entirely genetic & environmental risk factors can trigger/increase risk of developing it
- eg. cromer et al. (2007) found over half the OCD clients in sample had experienced traumatic event in their past & OCD was more severe in those with 1+ traumas
T: means genetic vulnerability only provides partial explanation for OCD
define neural explanations for OCD
genes associated with OCD likely to affect levels of key neurotransmitters & structures of the brain
2 neural explanations for OCD
- role of seretonin
- decision-making systems
describe the role of seretonin
- seretonin helps regulate mood
- neurotransmitters relay information from 1 neuron to the next
- if someone has low seretonin levels, normal transmission of mood-relevant information cannot happen & they may experience low moods (other mental processes may be affected)
- some cases of OCD explained by reduction in functioning of seretonin system
describe decision-making systems
- some cases of OCD (eg. hoarding disorder) seem to be associated with impaired decision-making
- may be associated with abnormal functioning in lateral parts of frontal lobe
- frontal lobes are responsible for logical thinking & making decisions
- evidence to suggest the left parahippocampal gyrus (processes unpleasant emotions) functions abnormally in OCD
neural explanations for OCD AO3 +) existence of research to support
E:
- antidepressants which work purely on serotonin are effective in reducing symptoms of OCD, suggesting seretonin is involved in OCD
- nestadt et al. (2010): OCD symptoms form part of conditions known to be biological in origin, eg. parkinson’s disease, which causes muscle tremors & paralysis
- if biological disorder produces OCD symptoms, then we can assume biological processes underlie OCD
T: suggests biological factors (eg. seretonin, process underlying certain disorders) may be responsible for OCD
neural explanations for OCD AO3 -) seretonin-OCD link may not be unique to OCD
E:
- many people with OCD experience clinical depression
- having 2 disorders is called co-morbidity
- this depression likely involves disruption to action of seretonin
- could simply be that seretonin activity is disrupted in many people with OCD as they are depressed as well
T: means seretonin may not be relevant to OCD symptoms
