Lesson 12 The biological approach to explaining OCD - genetic and neural explanations Flashcards
The COMT gene
· Genes come in different forms (alleles) and it seems that genes could be the main cause of OCD.
· OCD might be inherited whereby sufferers have a genetic vulnerability or a genetic predisposition to get the illness
· Psychologists often use family or twin studies to investigate genetics
· OCD has been classed as polygenic; this means that one single gene is not responsible for the disorder.
· Instead, many genes might be responsible for causing OCD; and they are known as, candidate genes.
· The COMT gene causes OCD. The COMT gene regulates the production of the neurotransmitter dopamine where high levels are associated with OCD.
· High levels of dopamine are responsible for drive, motivation and aggression
· The COMT gene has been found to be more common in OCD patients than people who do not have the illness.
The SERT gene
· This gene affects the transportation of serotonin which results in low levels of serotonin (resulting in low mood and depressive symptoms)
· Individuals have the SERT gene on chromosome 17. It seems a mutation 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. The gene mutates which then causes low levels of serotonin to be produced. It seems that there is a link with OCD and depression and this might account for it.
· Therefore it seems that OCD does have a genetic basis.
Advantages of genetic explanations
- Nestadt (2000) supports the genetic explanation for OCD. He found that people who had a first degree relative who already had OCD were five times more likely to also get the illness. This supports the idea that OCD is transmitted genetically
- Billett (1998) supports the idea that OCD is transmitted genetically. He found from a meta-analysis of 14 twin studies that OCD is twice more likely to be concordant in identical monozygotic twins rather than dizygotic non identical twins. Therefore this supports the idea that OCD is transmitted by genetics
Disadvantages of genetic explanations
- A criticism of the genetics explanation is that the concordance rate for OCD is not 100%. Therefore OCD cannot be caused entirely by genetic factors. The genetics explanation fails to take into account psychological and environmental factors that might contribute to the cause of OCD
- A criticism for the genetics explanation for OCD is that it is polygenic and one single gene is not responsible for causing the disorder. OCD has been genetically linked to other illnesses such as Tourette’s syndrome, and autism. Therefore it seems that the genetic cause for OCD is very complex and might be related to other illness too. It could be that one specific gene is not responsible for OCD, but could be a predisposing factor.
- The behavioural approach would contradict the genetic explanation for OCD. The two process model would suggest that OCD can be learnt via classical conditioning, and then rewarded through reinforcement (operant conditioning). The behavioural approach has gained a great deal of support in explaining the cause of OCD, especially as OCD is often treated using behavioural therapies such as exposure (which is similar to systematic desensitisation).
- The diathesis stress model would argue that OCD can be caused by a combination of genes and a trigger in the environment (stress). Therefore genes alone cannot be the only cause of OCD; genes would need to be combined with other factors in order for the disorder to develop. The diathesis stress model would weaken the genetics argument
Research by Beekman and Cath into genetics and OCD
· A meta-analysis was conducted of twin studies and OCD
· MZ twins were compared against DZ twins
· OCD patients had been diagnosed with OCD using older criteria (before the DSM and ICD)
· The psychologists also examined studies whereby OCD patients had been diagnosed using DSM criteria
· 10,034 twin pairs were studied overall
· The results found that in children, OCD is inherited via genes and the genetic influence ranges from 45-65%
· The results found that in adults, OCD is inherited via genes and the genetic influence ranges from 27-47%
· The conclusion was that OCD is transmitted genetically and this was more apparent when examining children rather than adults.
Disadvantages of the research by Beekman and Cath
- The research can be criticised because the majority of the twin studies were not performed in controlled conditions. This means that the data is not very objective or scientific and therefore this might affect the validity and the reliability of the results gained from this research. This might question the idea that OCD is genetic
- The research can be criticised because gene mapping was not taken into consideration when looking at whether OCD is genetic. Gene mapping would look closely at the DNA of the twins that had OCD and compare this with twins that do not have OCD. A comparison need to be made in order to make the results more valid and robust.
Advantages of the research by Beekman and Cath
- A very large sample size, over 10,000 twins, representative and reliable
- Used a meta analysis
What are the genetic causes of OCD
The COMT gene and the SERT gene
What are the neural causes of OCD
High levels of dopamine and low levels of serotonin
Dopamine
· Dopamine is a neurotransmitter that affects mood and might be a cause of OCD
· The 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, which is similar to what OCD sufferers would experience.
· High dopamine levels have also been linked to over activity in the basal ganglia area in the brain (motor function and learning).
Serotonin
· Serotonin is a neurotransmitters that affects mood and might be a cause of OCD
· The frontal lobes in the brain have been linked to serotonin activity.
· OCD sufferers tend to have low levels of serotonin and this can cause depressive like symptoms and also obsessive thoughts
· Many OCD sufferers are depressed due to the 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.
Advantages of neural explanations
- There has been a great deal of research support to state that neurotransmitters do cause OCD. Anti depressant drugs will increase serotonin levels in OCD patients, and this has led to a reduction of OCD symptoms. Therefore there is good evidence to suggest that low levels of serotonin could be a cause for OCD
- Research conducted by Ciccerone (2000) would support the neural explanations of OCD. He found that giving OCD patient’s low doses of the drug Risperidone helped to lower dopamine levels and alleviate some of the symptoms of OCD. Therefore it seems that high levels of dopamine could be a biological cause for OCD
- Menzies (2007) suggested research evidence that would support a genetic link to abnormal levels of neurotransmitters. Menzies studied MRI scans (magnetic resonance imaging) in OCD patients and their immediate family members and compared them with healthy controls. It was found that OCD patients and their families had reduced grey matter in key regions of the brain and they had an unusual neuroanatomy. It was concluded that OCD can be caused by abnormal brain structure which could be inherited via genes
Disadvantages of neural explanations
- A disadvantage of the neural explanation is that neurotransmitters such as dopamine and serotonin might not necessarily cause OCD. Instead low levels of serotonin and high levels of dopamine might be the effect of OCD. Therefore we must be cautious when looking at cause and effect of neurotransmitters
- A problem with the neural explanation is that OCD is co morbid with depression (exists alongside depression). Therefore it is not clear whether low levels of serotonin cause OCD or depression or both? Therefore the link between low levels of serotonin causing OCD is not very clear and needs to be investigated further
- The role of dopamine causing OCD has been questioned. It has been found that high levels of dopamine can also cause other psychological illnesses and not just OCD. For instance high dopamine can cause bipolar depression and schizophrenia. Therefore there is not enough research evidence to suggest the high levels of dopamine can cause OCD to occur. A combination of factors might be responsible for causing the illness
Neural explanation of OCD - Neuroanatomy by Jenike and Rauch
· There might be a relationship between OCD being caused by some types of brain damage which might be caused by a virus
· The brain damage might cause a problem in the short term memory that causes a chain reaction of the person doubting whether they have performed a certain action (e.g. did I lock the front door?) This is a common characteristic of OCD and might then result in repetitive behaviour (compulsions) of repeatedly locking/checking that the front door is locked.
· OCD patients were studied using PET scans (position emission tomography). They were shown an image of something dirty (they had a cleaning obsession). Evidence found that the frontal lobes and the basal ganglia were the most active parts of the brain (compared to non OCD sufferers). It seems the basal ganglia might be overactive
· The basal ganglia seems to malfunction in OCD sufferers.
· The basal ganglia refers to a series of interconnected brain structures that are at the front of the brain (near the orbital frontal cortex, which also seems to be overactive in OCD patients). The basal ganglia is responsible for control of voluntary motor movements, procedural learning, habit learning, eye movements, cognition, and emotion. An overactive basal ganglia can lead to repetitive motor functions
· Patients who have Tourette’s syndrome also have problems with the basal ganglia, and it seems that many patients who have Tourette’s also have OCD.
· 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.
Advantages of neural explanations of OCD
- A strength of the neural explanation is that it uses PET scanning, this means that it is objective and scientific, therefore making it reliable
- The Psychologist Rapoport (1990) found supporting evidence about neural causes of OCD. He 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. Rapoport found that after this epidemic there was a major rise in the number of OCD cases reported. This might be because the viral infection caused damage or brain abnormality that contributed to the development of OCD. This supports the idea about neural causes of OCD
