Biological Approach: Explaining OCD Flashcards
What are genetic explanations of OCD?
-Genes are involved in individual vulnerability to OCD
-In a study 37% OCD patients had parents with OCD and 21% had siblings with OCD
-Another study found first degree relatives of a patient had an 11.7% chance of developing condition compared to 2.7% chance in those with first degree relatives without OCD
What have twin studies shown?
-Twins have been used to investigate role of genes in OCD
-MZ twins are genetically identical and share similar environments - if one twin develops OCD so should the other
-Miguel found if on MZ twin has OCD, there is a 53-87% chance of the other developing it.
-DZ twins share half genes - 22-47% chance of both suffering from OCD
What candidate genes have been implicated in OCD?
5HT1-D Beta
-Implicated in the efficiency of transport of serotonin across synapses
COMT
-Regulates production of dopamine
-More common in OCD
-Produces lower activity of COMT gene and higher levels of dopamine
SERT
-Affects transport of serotonin
-Creates lower levels of serotonin
How is OCD polygenic?
-Means OCD is not caused by a single gene, several involved
-Taylor 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 and serotonin
What is a strength of genetic explanations of OCD?
Support from family and twin studies:
-Nestadt identified 80 patients with OCD and 343 of their first degree relatives and compared them with 73 control patients without mental illness and 300 of their relatives
-Found people with first degree relative with OCD were x5 more likely to suffer
This suggests OCD must have a genetic basis, thus supporting the biological approach to explaining OCD
What is a limitation of genetic explanations of OCD?
Environmental factors can’t be ignored:
-Research indicates a genetic component = flawed
-If OCD was a genetic condition then we would expect a 100% concordance rate for MZ twins as they share 100% genes
However the actual rate is approx 50-60% suggesting there must be an environmental contribution
What are neural explanations?
-Idea that genes associated with OCD will affect levels of neurotransmitters as well as structures of the brain
What are neurotransmitters?
Responsible for relaying info from one neuron to the other
What is the role of serotonin?
-Believed to regulate mood and implicated in sleep, memory, emotions, appetite and social and sexual behaviour
-It is thought that it has a role in preventing repetition of tasks
-A lack of serotonin results in loss of a mechanism that inhibits task repetition
-Suggested that if someone has low levels, the normal transmission of mood-relevant info does not take place and mood is affected
What is the role of dopamine?
-Dopamine are believed to be abnormally high in OCD people
-Based on animal studies
-High levels of dopamine in the animals resembled the behaviours of compulsive behaviour found in OCD people
What brain structures are associated with OCD?
Orbitofrontal cortex
-Helps us make intelligent choices and associated with high-level thinking and conversion of sensory info into thoughts and actions
-Helps us emotionally estimate outcomes of a future behaviour
-Safety checks (in response to sensory inputs) (eg. greasy countertop = clean it)
-OD have difficulty turning off or ignoring impulses so they will wash the countertop 50x
-FMRI’s show hyperactivity in this part of the brain
-Hence why they focus on compulsive behaviour and estimate what might happen because they did or didn’t do something (often irrational)
EG. didn’t lock the door so someone will break in and kill family
What is 1 strength to neural explanations?
Based on objective techniques
-Saxena and Rauch reviewed studies of OCD that used PET, fMRI and neuro imaging techniques
-Found consistent association between orbital frontal cortex and OCD symptoms
-Suggests neural mechanisms are involved with disorder
Brain scanning techniques provide objective scientific and valid findings increasing our confidence in the link between neural mechanisms and OCD
What is 1 weakness to neural explanations?
Problems with cause and effect
-Clear evidence that various neurotransmitters and structures of the brain do not function adequately or as they should in OCD patients
However, this does not mean that these abnormalities cause OCD, OCD could cause the abnormalities
