biological explanation of OCD Flashcards
biological approach definition
a perspective that emphasise the importance of physical processes in the body such as genetic inheritance and neural function
genetic explanation defintion
genes make up chromosomes an consist of DNA which codes the physical features of an organism (such as eye colour and height) and psychological features such as metal disorder and intelligence. genes are transmitted from parents to offspring
neural explanations definition
the view that physical and psychological characteristics are determines by the behaviour of the nervous system, in particular the brain as well as individual neurons
what are the 2 biological explanations of OCD
-genetic
-neural
what is the genetic explanation of OCD
some mental disorders appear to have a stronger biological component than others, and OCD may be largely understood as biological in nature. one form of biological explanation is the genetic explanation
how are genes involved in OCD
genes are involved in the individual vulnerability in OCD
Lewis 1936 study of genes in OCD
-observed that 37% of his OCD patients had parents with OCD and 21% had siblings. this suggests that OCD runs in families, although what is probably passed on is genetic vulnerability not the certainty of OCD
what does the diathesis-stress model say about OCD
certain genes leave some people more likely to develop a mental disorder but its not certain. some environmental stress (experience) is necessary to trigger the condition
what are candidate genes
researchers have identified some genes which create vulnerability for OCD.
examples of candidate genes
some of these genes are involved in regulating development of the serotonin system. for example, gene 5HT1-D beta is implicated in the transport of serotonin across synapses
what does OCD being polygenic mean
OCD is not caused by one single gene but by a combination of genetic variation that together significantly increase vulnerability
what did Taylor 2013 find about OCD being polygenic
analysed findings of previous studies and found evidence that up to 230 different genes may be involved in OCD. genes that have been studies in relation to OCD include those associated with the action of dopamine as well as serotonin, both neurotransmitters believed to have a role in regulating mood
what has been found about different types of OCD
-one group of genes may cause OCD in one person but a different group of genes may cause ethe disorder in another person which means OCD is aetiologically heterogeneous meaning the origins(aetiology) of OCD very from one person to another (heterogenous)
what does evidence show different types of OCD may be the result of
particular genetic variations, such as hoarding disorder and religious obsession
what is the neural explanation of OCD
genes associated with OCD are likely to affect the levels of key neurotransmitters as well as structures in the brain.
what are the 2 neural explanations of OCD
-role of serotonin
-decision-making systems
what is the neural explanation for the role of serotonin
-neurotransmitter believed to help regulate mood. neurotransmitters are responsible for relaying information from one neuron to another. if a person has low levels of serotonin then normal transmission of mood-relevant information does not take place and a person may experience low moods (and other mental processes may be affected). at least some cases of OCD may be explained by a reduction in the functioning of serotonin system in the brain
decision-making systems
in some cases of OCD particularly hoarding disorder, seem to be associated with impaired decision-making. this in turn may be accosicted with abnormal functioning of the lateral of the the frontal lobed of the brain. the frontal lobed are the front part of the brain (behind forehead) that are responsible for logical thinking and making decisions. there is evidence to suggest the an area called the left parahippocampal gyrus, associated with processing unpleasant emotions, functions abnormally in OCD
strength of genetic explanation of OCD - research support
-strong evidence base
-evidence from a variety of sources which strongly suggests that some people are vulnerable to OCD as a result of their genetic makeup. one source of evidence is twin studies. in one study Nestadt et al 2010 reviewed twin studies and found that 68% of identical twins shared OCD as opposed to 31% of non-identical twins. another source of evidence for a genetic influence on OCD is family studies. research has found that a person with a family member diagnosed with OCD is around four times as likely to develop it as someone without (marini and Stebnicki 2012) –> research studies suggest that there must be some genetic influence on development of OCD
limitation of genetic explanation of OCD - environmental risk factors
-also environmental risk factors
-strong evidence for the idea that genetic variation can make a person more or less vulnerable to OCD. however, OCD does not appear to be entirely genetic in origin and it seem environmental risk factors can also trigger or increase the risk of developing OCD. in one study Cromer et al 2007 found that over half of the OCD clients in their sample had experienced a traumatic event in their past. OCD was also more severe in those with one or more traumas –> means that genetic vulnerability only provides a partial explanation for OCD
evaluation of genetic explanation of OCD - animal studies
-proved difficult to find candidate genes (genetic variations that are possible causes of OCD). there is evidence though from animal studies showing that particular genes are associated with repetitive behaviours in other species, for example mice (Ahmari 2016)
-however, although mice and humans share most genes, the human mind and brain are much more complex, and it may not be possible to generalise from animal repetitive behvaiour to human OCD
strength of neural explanation of OCD - research support
-existence of some supporting evidence
-antidepressants that work purely on serotonin are effective in reducing OCD symptoms and this suggests that serotonin may be involved in OCD. also, OCD symptoms form part of conditions that are known to be biological in origin, such as the degenerative brain disorder Parkinson’s disease, which caused muscle tremors and paralysis (Nestadt et al 2010). if a biological disorder produces OCD symptoms, then we may assume the biological processes underlie OCD –> suggests that biological factors such as serotonin and the process underlying certain disorders may be responsible for OCD
limitation of neural explanation of OCD - no unique neural system
-serotonin-OCD kink may not be unique to OCD
-many people with OCD also experience clinical depression. having two disorders together is called co-morbidity. this depression probably involved (though is not necessarily caused by) disruption to the action of serotonin. this leaves us with a logical problem when it comes to serotonin as a possible basis for OCD. it could simply be that serotonin activity is disrupted in many people with OCD because they are depressed as well –> means serotonin may not not be relevant to OCD symptoms
evaluation of neural explanation of OCD - correlation and causality
-evidence to show that some neural symptoms such as serotonin do not work normally in people with OCD. according to the biological model of mental disorder this is most easily explained by brain dysfunction causing the OCD
-however, this is simply a correlation between neural abnormality and OCD, and such correlation do not necessarily indicate a casual relationship. it is quite possible that the the OCD (or its accompanying depression) causes the abnormal brain function or both are influenced by a third factor
