lesson 12 biological causes of OCD Flashcards
Genetic causes of ocd
-genes come in different form (alleles) and it seems that genes could be the main cause of ocd
-ocd might be inherited whereby sufferers have a genetic vulnerability/predisposition to get the illness
-often use family or twin studies to investigate genetics
-ocd has been classed as polygenic, not just one single gene is responsible for disorder instead meant genes might be responsible, known as candidate genes
COMT gene
-causes ocd, regulates the production of the neurotransmitter dopamine which in high levels associated with ocd
-high levels of dopamine are responsible for drive, motivation and possibly aggression
-found to be more common in ocd patients than in people who do not have ocd
SERT gene
-affects the transportation of serotonin which results in low levels leading to low mood and depressive symptoms
-Individuals have the SERT gene on chromosome 17, seems a mutations in this gene can cause ocd
-research conducted by Ozaki (2003) found evidence that 6 out of 7 family members who had ocd had a mutation of the SERT, gene mutates which then causes low levels of serotonin, seems there is a link with ocd and depression and this could account for it
-ocd does have a genetic basis
Genetics and ocd ao3
-Nestadt (2000) supports the genetic explanation, found people who had first degree relative who already had ocd were five times more likely to also get the illness, supports idea it is transmitted genetically
-Billett (1998) supports idea, found from a meta analysis of 14 twin studies that ocd is twice more likely to be concordant in idential mz twins rather than dz twins, supports ocd transmitted by genetics
-concordance rate for ocd is not 100%, therefore cannot be entirely caused by genetic factors, fails to take into account psychological and environmental factors that might contribute
-ocd is polygenic, one single gene is not responsible for causing the disorder, ocd has been genetically linked to other illness such as tourettes and autism, genetic cause for ocd is very complex and might be related to other illnesses, could be a predisposing factor
-behavioural approach contradicts, two process model suggests that ocd can be learnt and rewarded, gained a great deal of support in explaining ocd, behavioural therapies to treat it
-diathesis stress model argues that ocd can be caused by a combination of genes and a trigger in the environment, therefore genes alone cannot be the only cause of ocd, genes would need to be combined with other factors for the disorder to develop, weakens the genetics argument
genetics and ocd research
-Beekman and Cath 2005
-meta analysis of twin studies into ocd that had occured in the last 70 years
-mz twins compared against dz twins
-examined studies between 1929-1965 where ocd patients had been diagnosed using older criteria before DSM and ICD
-also examined studies after 2965 whereby ocd patients had been diagnosed using DSM critieria
-10034 twin pairs were studied overall, from 28 separate twin studies, from 1929-1965 there were 37 pairs of twins, from 1965 onwrds there were 9997 pairs of twins
-results found that in children ocd is inherited via genes and the genetic influce ranges from 45-65%
-results found that in adults ocd is inherited via genes and the genetic influce ranges from 27-47%
-conclusion that ocd is transmitted genetically and this was more apparent when examining children rather than adults
genetics and ocd research ao3
-majority of twin studies were not performed in controlled conditions, means that data is not very objective or scientific and therefore might affect the validity and reliability of the results, might question the idea that ocd really is genetics
-gene mapping was not taken into consideration when looking at whether ocd is genetic, gene mapping would look very closely at the dna of the twins that had ocd and compare this with twins that do not have ocd, a comparison needs to be made in order to make the results more valid and robust
-meta analysis means large sample, increases reliability
neural explanations of ocd
neurotransmitters and biochemistry
dopamine and ocd
-neurotransmitter that affects mood and might be a cause of ocd
-frontal lobes in the brain have been linked to dopamine activity
-ocd sufferers have high levels of dopamine
-research conducted on animals has found that high doses of drugs that enhance dopamine levels can induce movements that resemble compulsive and repetitive behaviour
-high dopamine levels have also been linked to over activity in the basal ganglia area in the brain (motor functioning and learning)
serotonin and ocd
-neurotransmitter that effects mood and might be a cause of ocd
-frontal lobes associated with serotonin activity
-ocd sufferers tend to have low levels of serotonin and this can cause depressive symptoms and obsessive thoughts
-many ocd sufferers are depressed due to low levels of serotonin
-serotonin plays a key role in operating the caudate nucleus in the brain and it seems that low levels of serotonin cause the caudate nucleus to malfunction
-plays a vital role in how the brain learns, specifically storing and processing of memories, works as a feedback processor, which means it uses information from past experiences to influence future actions and decisions, ocd patients have a malfunctioning caudate nucleus
neural explanations of ocd ao3
-great deal of research support to state neurotransmitters cause ocd, anti depressant drugs will increase serotonin levels in ocd pateients and has led to a reduction of symptoms,good evidence to suggest that low levels of serotonin could be a cause of ocd
-neurotransmitters may not necessarily cause ocd, instead low levels of serotonin and high levels of dopamine might be the effect of ocd, must be cautious when looking at cause and effect
-ocd is co morbid with depression therefore it is not clear whether low levels of serotonin cause ocd or depression or both, therefore the link between low levels od serotonin causing ocd is not vert clear and needs to be investigated
-Ciccerone (2000) found that giving ocd patients low doses of the drug risperidone helped to lower dopamine levels and alleviate some of the symptoms of ocd, seems high levels of dopamine could be a biological cause for ocd
-Menzies (2007) studied MRI scans in ocd patients and their immediate family members and compared them with healthy controls, it was found ocd patients and their families had reduced grey matter in key regions of the brain and they had unusual neural anatomy, concluded that ocd can be caused by abnormal brain structure which could be inherited via genes
-role of dopamine has been questioned, high levels of dopamine has been found to cause other psychological illnesses not just ocd, therefore not enough research evidence to suggest high levels of dopamine can cause ocd, combination of factors might be responsible
neuroanatomy and ocd research
-Jenike and Rauch
-might be a relationship between ocd being caused by some types of brain damage which might be caused by a virus
-brain damage might then cause a problem in the short term memory that causes a chain reaction of the person doubting whether they have performed a certain action recently, common characteristic of ocd and might result in repetitive behaviour
-ocd patients were studied using PET scans, shown an image of something dirty, evidence found that frontal lobes and basal ganglia were most active parts of the brain, seems basal ganglia might be overactive
-basal ganglia seems to malfunction in ocd sufferers, refers to a series of interconnected brain structures that are at the front of the brain, responsible for control of voluntary motor movements, procedural learning, habit learning, eye movements, cognition and emotion, overactive can lead to repetitive functions
-further research has found that ocd sufferers might have damage to the frontal cortex of the brain, this part of the brain is involved in selecting, controlling and inhibiting behaviour which ocd patients struggle with
neural explanations of ocd ao3
-cause and effect not clear
-uses PET scanning, scientific objective methods
-Rapoport (1990) reviewed an epidemic that occurred in Europe between 1916-1918 called the great sleeping sickness, there was widespread viral brain infections across Europe at this time, found that after this epidemic there was a major rise in the number of ocd cases reported, might be because the viral infection caused damage or brain abnormality that contributed to development of ocd, supports neural causes of ocd
